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Sample records for ac conductivity spectrum

  1. Study of AC electrical conduction mechanisms in an epoxy polymer

    NASA Astrophysics Data System (ADS)

    Jilani, Wissal; Mzabi, Nissaf; Gallot-Lavallée, Olivier; Fourati, Najla; Zerrouki, Chouki; Zerrouki, Rachida; Guermazi, Hajer

    2015-11-01

    The AC conductivity of an epoxy resin was investigated in the frequency range 10^{-1} - 106 Hz at temperatures ranging from -100 to 120 °C. The frequency dependence of σ_{ac} was described by the law: σ_{ac}=ω \\varepsilon0\\varepsilon^''_{HN}+Aωs. The study of temperature variation of the exponent (s) reveals two conduction models: the AC conduction dependence upon temperature is governed by the small polaron tunneling mechanism (SPTM) at low temperature (-100 -60 °C) and the correlated barrier hopping (CHB) model at high temperature (80-120 °C).

  2. Evolution of AC conductivity of wet illitic clay during drying

    NASA Astrophysics Data System (ADS)

    Csáki, Š.; Štubňa, I.; Trnovcová, V.; Ondruška, J.; Vozár, L.; Dobroň, P.

    2017-02-01

    The evolution of the AC electrical conductivity during drying as well as the relationship between sample volume and moisture of green illite samples were investigated. The samples were prepared from illitic clay (80 mass % illite, 4 mass % montmorillonite, 12 mass % quartz and 4 mass % of orthoclase) and distilled water with initial moisture content 36 mass % and were freely dried in air. Conductivity was measured by the volt-ampere method with AC power supply of 5 V in the frequency range from 50 Hz to 10 kHz. The AC conductivity steeply increased with increasing moisture, up to 15 mass %. At higher values of the moisture, the AC conductivity was high and almost constant. The volume of samples increased with increasing moisture when the moisture was higher than 8 mass %. Below this value, the dimensions of samples do not significantly change. The dependence of the relative volume change on moisture is presented in a form of the Bigot’s curve.

  3. AC Conductivity Studies of Lithium Based Phospho Vanadate Glasses

    NASA Astrophysics Data System (ADS)

    Nagendra, K.; Babu, G. Satish; Reddy, C. Narayana; Gowda, Veeranna

    2011-07-01

    Glasses in the system xLi2SO4-20Li2O-(80-x) [80P2O5-20V2O5] (5⩾x⩾20 mol%) has been prepared by melt quenching method. Dc and ac conductivity has been studied over a wide range of frequency (10 Hz to 10 MHz) and temperature (298 K-523 K). The dc conductivity found to increase with increase of Li2SO4 concentration. The ac conductivities have been fitted to the Almond-West type single power law equation σ(ω) = σ(0)+Aωs where `s' is the power law exponent. The ac conductivity found to increase with increase of Li2SO4 concentration. An attempt is made to elucidate the enhancement of lithium ion conduction in phosphor-vanadate glasses by considering the expansion of network structure.

  4. Impedance, AC conductivity and dielectric behavior Adeninium Trichloromercurate (II)

    NASA Astrophysics Data System (ADS)

    Fersi, M. Amine; Chaabane, I.; Gargouri, M.

    2016-09-01

    In this work, we report the measurements impedance spectroscopy technique for the organic-inorganic hybrid compound (C5H6N5) HgCl3, 11/2H2O measured in the 209 Hz-5 MHz frequency range from 378 to 428 K. Besides, the Cole-Cole (Z″ versus Z‧) plots were well fitted to an equivalent circuit built up by a parallel combination of resistance (R), fractal capacitance (CPE) and capacitance (C). Furthermore, the AC conductivity was investigated as a function of temperature and frequency in the same range. The experiment results indicated that AC conductivityac) was proportional to σdc + A ωS . The obtained results are discussed in terms of the correlated barrier hopping (CBH) model. An agreement between the experimental and theoretical results suggests that the AC conductivity behavior of Adeninium Trichloromercurate (II) can be successfully explained by CBH model. The contribution of single polaron hopping to AC conductivity in a present alloy was also studied.

  5. AC Conductivity Studies of Lithium Based Phospho Vanadate Glasses

    SciTech Connect

    Nagendra, K.; Babu, G. Satish; Gowda, Veeranna; Reddy, C. Narayana

    2011-07-15

    Glasses in the system xLi{sub 2}SO{sub 4}-20Li{sub 2}O-(80-x) [80P{sub 2}O{sub 5}-20V{sub 2}O{sub 5}](5{>=}x{>=}20 mol%) has been prepared by melt quenching method. Dc and ac conductivity has been studied over a wide range of frequency (10 Hz to 10 MHz) and temperature (298 K-523 K). The dc conductivity found to increase with increase of Li{sub 2}SO{sub 4} concentration. The ac conductivities have been fitted to the Almond-West type single power law equation {sigma}({omega}) = {sigma}(0)+A{omega}{sup s} where 's' is the power law exponent. The ac conductivity found to increase with increase of Li{sub 2}SO{sub 4} concentration. An attempt is made to elucidate the enhancement of lithium ion conduction in phosphor-vanadate glasses by considering the expansion of network structure.

  6. AC Conductivity and Dielectric Properties of Borotellurite Glass

    NASA Astrophysics Data System (ADS)

    Taha, T. A.; Azab, A. A.

    2016-10-01

    Borotellurite glasses with formula 60B2O3-10ZnO-(30 - x)NaF- xTeO2 ( x = 0 mol.%, 5 mol.%, 10 mol.%, and 15 mol.%) have been synthesized by thermal melting. X-ray diffraction (XRD) analysis confirmed that the glasses were amorphous. The glass density ( ρ) was determined by the Archimedes method at room temperature. The density ( ρ) and molar volume ( V m) were found to increase with increasing TeO2 content. The direct-current (DC) conductivity was measured in the temperature range from 473 K to 623 K, in which the electrical activation energy of ionic conduction increased from 0.27 eV to 0.48 eV with increasing TeO2 content from 0 mol.% to 15 mol.%. The dielectric parameters and alternating-current (AC) conductivity ( σ ac) were investigated in the frequency range from 1 kHz to 1 MHz and temperature range from 300 K to 633 K. The AC conductivity and dielectric constant decreased with increasing TeO2 content from 0 mol.% to 15 mol.%.

  7. Correction of the power law of ac conductivity in ion-conducting materials due to the electrode polarization effect.

    PubMed

    Khamzin, A A; Popov, I I; Nigmatullin, R R

    2014-03-01

    Based on the supposition related to fractal nature of transport processes in ion-conducting materials, an expression for the low-frequency ac conductivity dependence was derived. This expression for the ac conductivity generalizes the power-law dependence and gives a possibility to take into account the influence of the electrode polarization effect. The ac conductivity expression obtained is in excellent agreement with experimental data for a wide frequency range.

  8. AC conductivity studies of Fe doped TiO2 nanotubes

    NASA Astrophysics Data System (ADS)

    Vijayan, P. P.; Thomas, M.; George, K. C.

    2015-02-01

    Fe-doped TiO2 nanotubes are prepared by the combination of sol-gel process with hydrothermal treatment. The morphology and crystalline structure of TiO2 nanotubes are characterized by transmission electron microscopy (TEM), X-ray diffraction respectively (XRD). Fe doping induces a structural transformation from anatase to rutile. The temperature dependence of the ac electrical conductivity is investigated in the temperature range 303-413 K. Positive temperature coefficient of resistance is observed in the Fe doped TiO2 nanotubes. PL spectrum shows the presence of oxygen vacancies and self trapped excitons in Fe doped TiO2 nanotubes and undoped samples.

  9. The effect of bone conduction microphone placement on intensity and spectrum of transmitted speech items.

    PubMed

    Tran, Phuong K; Letowski, Tomasz R; McBride, Maranda E

    2013-06-01

    Speech signals can be converted into electrical audio signals using either conventional air conduction (AC) microphone or a contact bone conduction (BC) microphone. The goal of this study was to investigate the effects of the location of a BC microphone on the intensity and frequency spectrum of the recorded speech. Twelve locations, 11 on the talker's head and 1 on the collar bone, were investigated. The speech sounds were three vowels (/u/, /a/, /i/) and two consonants (/m/, /∫/). The sounds were produced by 12 talkers. Each sound was recorded simultaneously with two BC microphones and an AC microphone. Analyzed spectral data showed that the BC recordings made at the forehead of the talker were the most similar to the AC recordings, whereas the collar bone recordings were most different. Comparison of the spectral data with speech intelligibility data collected in another study revealed a strong negative relationship between BC speech intelligibility and the degree of deviation of the BC speech spectrum from the AC spectrum. In addition, the head locations that resulted in the highest speech intelligibility were associated with the lowest output signals among all tested locations. Implications of these findings for BC communication are discussed.

  10. Broadband AC Conductivity of XUV Excited Warm Dense Gold

    NASA Astrophysics Data System (ADS)

    Chen, Z.; Tsui, Y.; Toleikis, S.; Hering, P.; Brown, S.; Curry, C.; Tanikawa, T.; Hoeppner, H.; Levy, M.; Goede, S.; Ziaja-Motyka, B.; Rethfeld, B.; Recoules, Vanina; Ng, A.; Glenzer, S.

    2015-11-01

    The properties of ultrafast laser excited warm dense gold have been extensively studied in the past decade. In those studies, a 400nm ultrashort laser pulse was used to excite the 5 d electrons in gold to 6s/p state. Here we will present our recent study of warm dense gold with 245eV, 70fs pulses to selectively excite 4 f electrons using the XUV-FEL at FLASH. The AC conductivity of the warm dense gold was measured at different wavelengths (485nm, 520nm, 585nm, 640nm and 720nm) to cover the range from 5 d-6 s / p interband transitions to 6 s/ p intraband transitions. Preliminary result suggests that the onset of 5 d-6 s / p band transition shifts from 2.3eV to ~ 2eV, which is in agreement with the study of 400nm laser pulse excited warm dense gold. More detailed analysis of our data will also be presented.

  11. AC impedance spectroscopy and conductivity studies of Dy doped Bi4V2O11 ceramics

    NASA Astrophysics Data System (ADS)

    Bag, Sasmitarani; Das, Parthasarathi; Behera, Banarji

    2017-03-01

    The ac impedance and conductivity properties of Dy doped Bi4V2 - x Dy x O11 (x = 0.05, 0.10, 0.15 and 0.20) ceramics prepared by solid-state reaction technique, in a wide frequency range at different temperatures have been studied. All the samples exhibited β-type phase orthorhombic structure at room temperature. The Nyquist plot confirmed the presence of both grain and grain boundary effects for all Dy doped samples. Double relaxation behavior was also observed. The grain and grain boundary resistance decreases with rise in temperature for all the concentration and exhibits a typical negative temperature co-efficient of resistance (NTCR) behavior. An analysis of the electric modulus suggests the possible hopping mechanism for electrical transport processes of all the materials. The ac conductivity spectrum obeys Jonscher's universal power law. DC conductivity of the materials were also studied and values of the activation energy found to be 0.40, 0.49, 0.73 and 0.78 eV for the compositions x = 0.05, 0.10, 0.15 and 0.20, respectively, at different temperatures (150-375 °C).

  12. AC conductivity of a niobium thin film in a swept magnetic field.

    PubMed

    Tsindlekht, M I; Genkin, V M; Gazi, S; Chromik, S

    2013-02-27

    We report results of measurements of the ac conductivity of a Nb superconducting thin film in a swept dc magnetic field. In the mixed state the swept dc field creates vortices at the film surface which pass through the film and form the observed ac conductivity. Vortex rate generation does not depend on the value of the dc field and there is a large plateau-like region of dc magnetic fields where the dissipation is approximately constant. A proposed phenomenological model describes quite well the main features of the ac response in these fields, including its dependency on the sweep rate, ac amplitude, frequency, and value of the second and third harmonics.

  13. Polaron conductivity mechanism in potassium acid phthalate crystal: AC-conductivity investigation

    NASA Astrophysics Data System (ADS)

    Filipič, Cene; Levstik, Iva; Levstik, Adrijan; Hadži, Dušan

    2016-08-01

    The complex dielectric constant, \\varepsilon *(ν ,T), of potassium acid phthalate monocrystal (KAP) was investigated over the broad frequency and temperature range. While the imaginary part of dielectric constant ε‧‧(ν) increases rapidly with increasing temperature in the studied temperature range, the real part of dielectric constant ε‧(ν) increases only at high temperatures; there is almost no change of ε‧(ν) below 200 K. Both values of ε‧ and ε‧‧ are frequency dependent; the values increase with decreasing frequencies. At temperatures below 450 K the ac electrical conductivity and dielectric constant follow simultaneously the universal dielectric response (UDR). The analysis of the temperature dependence of the UDR parameter s in terms of the theoretical model for small polarons revealed that this mechanism governs the charge transport in KAP crystal in the studied temperature range.

  14. Scaling of the holographic AC conductivity for non-Fermi liquids at criticality

    NASA Astrophysics Data System (ADS)

    Kiritsis, Elias; Peña-Benitez, Francisco

    2015-11-01

    The frequency dependence of the AC conductivity is studied in a holographic model of a non-fermi liquid that is amenable to both analytical and numerical computation. In the regime that dissipation dominates the DC conductivity, the AC conductivity is described well in the IR by a Drude peak despite the absence of quasiparticles. In the regime where pair-production-like processes dominate the conductivity there is no Drude peak. A scaling tail is found for the AC conductivity that is independent of the charge density and momentum dissipation. Evidence is given that this scaling tail σ AC ˜ ω m appears generically in quantum critical holographic systems and the associated scaling exponent m is calculated in terms of the Lifshitz and conduction critical exponents.

  15. AC motor controller with 180 degree conductive switches

    NASA Technical Reports Server (NTRS)

    Oximberg, Carol A. (Inventor)

    1995-01-01

    An ac motor controller is operated by a modified time-switching scheme where the switches of the inverter are on for electrical-phase-and-rotation intervals of 180.degree. as opposed to the conventional 120.degree.. The motor is provided with three-phase drive windings, a power inverter for power supplied from a dc power source consisting of six switches, and a motor controller which controls the current controlled switches in voltage-fed mode. During full power, each switch is gated continuously for three successive intervals of 60.degree. and modulated for only one of said intervals. Thus, during each 60.degree. interval, the two switches with like signs are on continuously and the switch with the opposite sign is modulated.

  16. Structural, dielectric and AC conductivity properties of Co2+ doped mixed alkali zinc borate glasses

    NASA Astrophysics Data System (ADS)

    Madhu, B. J.; Banu, Syed Asma; Harshitha, G. A.; Shilpa, T. M.; Shruthi, B.

    2013-02-01

    The Co2+ doped 19.9ZnO+5Li2CO3+25Na2CO3+50B2O3 (ZLNB) mixed alkali zinc borate glasses have been prepared by a conventional melt quenching method. The structural (XRD & FT-IR), dielectric and a.c. conductivityac) properties have been investigated. Amorphous nature of these glasses has been confirmed from their XRD pattern. The dielectric properties and electrical conductivityac) of these glasses have been studied from 100Hz to 5MHz at the room temperature. Based on the observed trends in the a.c. conductivities, the present glass samples are found to exhibit a non-Debye behavior.

  17. Ocular vestibular evoked myogenic potentials to air conduction (AC oVEMP): useful in clinical practice?

    PubMed

    Walther, L E; Rogowski, M; Hörmann, K; Schaaf, H; Löhler, J

    2011-01-01

    Cervical vestibular-evoked myogenic potential (cVEMP) and ocular VEMP (oVEMP) stimuli can be used to measure otolith function using air (AC) and bone conducted (BC) stimuli. Cervical VEMPs reflect saccular function and can be recorded using air conduction (AC), whereas oVEMPs reflect probably predominantly utricular function. Air- and bone-conducted vibration can be used, because AC oVEMP methodology seems to be fast and simple in clinical practice to measure otolith function. In this study we discuss the advantages and problems of AC oVEMP stimulation. AC oVEMP can be easily and quickly obtained within a few seconds. N10 (first negative peak) and p15 (first positive peak) latencies may be used as parameters for clinical interpretation but amplitude fluctuations are relatively large. For daily clinical use of VEMP visualization in a normogram seems feasible. Especially the AC oVEMP methodology (100 dB nHL, tone burst 500 Hz) is fast and efficient in clinical practice to measure otolith function, predominantly utricular function.

  18. Optical, electrical and ac conductivity measurements of nonlinear optical Dimethylaminomethylphthalimide doped with cadmium chloride single crystal for nano applications

    NASA Astrophysics Data System (ADS)

    Subramani, K.; Joseph, P. S.; Shankar, G.

    2013-07-01

    Single crystals of Dimethylaminomethylphthalimide cadmium chloride (DAMPCC) were grown by a slow evaporation technique. The unit cell parameters and crystal structure were measured by the powder X-ray diffraction analysis. The modes of vibrations of different molecular groups present in the DAMPCC crystal have been identified by FTIR spectral analysis. The UV-vis-NIR spectral analysis is used to study the optical behaviors like absorption and transmission properties of the crystal. The diffuse reflectance spectrum in absorption studies is calculated. The optical band gap of the DAMPCC crystal is calculated to be cut off wavelength 360 nm at photon energy 4.772 eV. The optical conductivity, electrical conductivity and ac conductivity are also calculated. Finally the nonlinear optics (NLO) property of DAMPCC crystal was confirmed by second harmonic generation (SHG) test using the Nd:YAG laser of fundamental wavelength 1064 nm.

  19. ac conductance in granular insulating Co-ZrO{sub 2} thin films: A universal response

    SciTech Connect

    Konstantinovic, Zorica; Garcia del Muro, Montserrat; Kovylina, Miroslavna; Batlle, Xavier; Labarta, Amilcar

    2009-03-01

    The ac conductance in granular insulating Co-ZrO{sub 2} thin films prepared by pulsed laser deposition is systematically studied as a function of the Co volume content x. An absorption phenomenon at low frequencies that mimics the universal response of disordered dielectric materials is observed in the range of metal content below the Co percolation threshold x{sub p}{approx_equal}0.35 in the so-called dielectric regime. The temperature and frequency dependences of this absorption phenomenon are successfully analyzed in terms of random competing conduction channels between Co particles through thermally assisted tunneling and capacitive conductance. The ac conductance is well correlated with the nanostructure of the samples obtained by the transmission electron microscopy and perfectly matches the calculated ac response for a random resistor-capacitor network. We also show the occurrence of fractional power-law dependences on the frequency of the ac conductance taking place at very low frequencies as compared to the typical ranges at which dispersive behavior is observed in classical-disordered dielectric materials.

  20. Dielectric behavior and ac electrical conductivity in samarium substituted Mg-Ni ferrites

    NASA Astrophysics Data System (ADS)

    Melagiriyappa, E.; Veena, M.; Somashekarappa, A.; Shankaramurthy, G. J.; Jayanna, H. S.

    2014-08-01

    Samarium substituted MgNi ferrites with composition Mg1-xNixFe2-ySmyO4 ( x = 0, 0.2, 0.4, 0.6, 0.8, 1.0; y = 0.0, 0.05, 0.1) have been prepared by ceramic method. Dielectric measurements of the samples have been carried out at room temperature as a function of frequency and composition. X-ray diffraction patterns have confirmed the single-phase spinel cubic structure for all the samples. Dielectric constant ( ɛ') and dielectric loss (tan δ) decrease while ac electrical conductivity ( σ ac ) increases with increase in frequency. Dielectric properties have been explained on the basis of Maxwell-Wagner's two layer model. The conduction mechanism in these ferrites is due to electron hopping between Ni2+ and Ni3+ as well as Fe3+ and Fe2+ ions on octahedral sites. Dielectric constant and ac conductivity increases and decreases respectively with nickel content. A significant reduction in the values of dielectric constant and ac electrical conductivity has been observed in Sm3+ ions substituted samples.

  1. Charging in the ac Conductance of a Double Barrier Resonant Tunneling Structure

    NASA Technical Reports Server (NTRS)

    Anantram, M. P.; Saini, Subhash (Technical Monitor)

    1998-01-01

    There have been many studies of the linear response ac conductance of a double barrier resonant tunneling structure (DBRTS), both at zero and finite dc biases. While these studies are important, they fail to self consistently include the effect of the time dependent charge density in the well. In this paper, we calculate the ac conductance at both zero and finite do biases by including the effect of the time dependent charge density in the well in a self consistent manner. The charge density in the well contributes to both the flow of displacement currents in the contacts and the time dependent potential in the well. We find that including these effects can make a significant difference to the ac conductance and the total ac current is not equal to the simple average of the non-selfconsistently calculated conduction currents in the two contacts. This is illustrated by comparing the results obtained with and without the effect of the time dependent charge density included correctly. Some possible experimental scenarios to observe these effects are suggested.

  2. AC Conductivity Studies in Lithium-Borate Glass Containing Gold Nanoparticles

    NASA Astrophysics Data System (ADS)

    Shivaprakash, Y.; Anavekar, R. V.

    2011-07-01

    Gold nanoparticles have been synthesized in a base glass with composition 30Li2O-70B2O3 using gold chloride (HAuCl4.3H2O) as a dopant. The samples are characterized using XRD, ESR, SEM and optical absorption in the visible range. AC conductivity studies have been performed at RT over a frequency range 100 to 10 MHz. The dc conductivity is calculated from the complex impedence plot. The dc conductivity is found to be increasing with the increase of dopant concentration. AC conductivity data is fitted with Almond-West law with power exponent `s'. The values of `s' is found to lie in the range of 0.70-0.73.

  3. Effective conductance method for the primordial recombination spectrum

    NASA Astrophysics Data System (ADS)

    Ali-Haïmoud, Yacine

    2013-01-01

    As atoms formed for the first time during primordial recombination, they emitted bound-bound and free-bound radiation leading to spectral distortions to the cosmic microwave background. These distortions might become observable in the future with high-sensitivity spectrometers, and provide a new window into physical conditions in the early universe. The standard multilevel atom method habitually used to compute the recombination spectrum is computationally expensive, impeding a detailed quantitative exploration of the information contained in spectral distortions thus far. In this work it is shown that the emissivity in optically thin allowed transitions can be factored into a computationally expensive but cosmology-independent part and a computationally cheap, cosmology-dependent part. The slow part of the computation consists in pre-computing temperature-dependent effective “conductances,” linearly relating line or continuum intensity to departures from Saha equilibrium of the lowest-order excited states (2s and 2p), that can be seen as “voltages.” The computation of these departures from equilibrium as a function of redshift is itself very fast, thanks to the effective multilevel atom method introduced in an earlier work. With this factorization, the recurring cost of a single computation of the recombination spectrum is only a fraction of a second on a standard laptop, more than four orders of magnitude shorter than standard computations. The spectrum from helium recombination can be efficiently computed in an identical way, and a fast code computing the full primordial recombination spectrum with this method will be made publicly available soon.

  4. Quantal Heating of Conducting Electrons with Discrete Spectrum

    SciTech Connect

    Vitkalov, S. A.; Bykov, A. A.

    2011-12-23

    Usually heating of conducting electrons by dc electric field results in an increase of electron temperature. In this paper we show that the dc heating of 2D electrons, placed in quantized magnetic fields, results in a peculiar electron distribution, which has the same broadening or an effective 'temperature' as the unbiased electron system. The quantal heating, however, violates strongly the Ohm's Law. In the conducting system with discrete electron spectrum the quantal heating results in spectacular decrease of electron resistance and transition of the electrons into a state with zero differential resistance (ZDR). Finally the heating leads to apparent dc driven metal-insulator transition, which correlates with the transition into the ZDR state. The correlation is very unexpected and is not understood.

  5. ac and dc percolative conductivity of magnetite-cellulose acetate composites

    SciTech Connect

    Chiteme, C.; McLachlan, D. S.; Sauti, G.

    2007-03-01

    ac and dc conductivity results for a percolating system, which consists of a conducting powder (magnetite) combined with an 'insulating' powder (cellulose acetate), are presented. Impedance and modulus spectra are obtained in a percolation system. The temperature dependence of the resistivity of the cellulose acetate is such that at 170 deg. C, it is essentially a conductor at frequencies below 0.059{+-}0.002 Hz, and a dielectric above. The percolation parameters, from the dc conductivity measured at 25 and 170 deg. C, are determined and discussed in relation to the ac results. The experimental results scale as a function of composition, temperature, and frequency. An interesting result is the correlation observed between the scaling parameter (f{sub ce}), obtained from a scaling of the ac measurements, and the peak frequency (f{sub cp}) of the arcs, obtained from impedance spectra, above the critical volume fraction. Scaling at 170 deg. C is not as good as at 25 deg. C, probably indicating a breakdown in scaling at the higher temperature. The modulus plots show the presence of two materials: a conducting phase dominated by the cellulose acetate and the isolated conducting clusters below the critical volume fraction {phi}{sub c}, as well as the interconnected conducting clusters above {phi}{sub c}. These results are confirmed by computer simulations using the two exponent phenomenological percolation equation. These results emphasize the need to analyze ac conductivity results in terms of both impedance and modulus spectra in order to get more insight into the behavior of composite materials.

  6. Investigation on the AC loss characteristics of MgB 2 wires by using a conduction cooling device

    NASA Astrophysics Data System (ADS)

    Jin, H. B.; Li, Z.; Ryu, K.

    2011-11-01

    In this study, we have experimentally investigated the AC loss characteristics of MgB2 wires with matrix of Fe and Cu by using a conduction cooling device. We fabricated the conduction cooling device to cool MgB2 wires down to 4 K. We also developed our unique test method, which is called AC pulse technique, to evaluate their AC loss characteristics within few hundred milliseconds. The test results show that the AC loss of the Fe/MgB2 wire is mainly generated in the ferromagnetic Fe matrix. Its AC loss is ten times larger than that of the Cu/MgB2 wire. In this paper, the evaluation technique of AC loss by using the conduction cooling device is described and the test results are discussed.

  7. Experimental and theoretical study of AC electrical conduction mechanisms of semicrystalline parylene C thin films.

    PubMed

    Kahouli, Abdelkader; Sylvestre, Alain; Jomni, Fethi; Yangui, Béchir; Legrand, Julien

    2012-01-26

    The electrical conduction mechanisms of semicrystalline thermoplastic parylene C (-H(2)C-C(6)H(3)Cl-CH(2)-)(n) thin films were studied in large temperature and frequency regions. The alternative current (AC) electrical conduction in parylene C is governed by two processes which can be ascribed to a hopping transport mechanism: correlated barrier hopping (CBH) model at low [77-155 K] and high [473-533 K] temperature and the small polaron tunneling mechanism (SPTM) from 193 to 413 K within the framework of the universal law of dielectric response. The conduction mechanism is explained with the help of Elliot's theory, and the Elliot's parameters are determined. From frequency- and temperature-conductivity characteristics, the activation energy is found to be 1.27 eV for direct current (DC) conduction interpreted in terms of ionic conduction mechanism. The power law dependence of AC conductivity is interpreted in terms of electron hopping with a density N(E(F)) (~10(18) eV cm(-3)) over a 0.023-0.03 eV high barrier across a distance of 1.46-1.54 Å.

  8. AC Conductivity and Diffuse Reflectance Studies of Ag-TiO2 Nanoparticles

    NASA Astrophysics Data System (ADS)

    Abdul Gafoor, A. K.; Musthafa, M. M.; Pradyumnan, P. P.

    2012-09-01

    Silver (Ag)-TiO2 nanoparticles synthesized by a low-temperature hydrothermal method in the anatase phase have been investigated by x-ray diffraction. Transmission electron microscopy has been used for morphological studies. Surface areas were studied by the Brunauer-Emmett-Teller method. Alternating-current (AC) conductivity and dielectric properties were studied for various dopant levels of 0.25 wt.%, 0.5 wt.%, and 1.0 wt.% at 300 K in the frequency range from 42 Hz to 5 MHz. AC conductivity and dielectric properties of TiO2 nanoparticles were greatly affected by loading with Ag. At high frequencies, the materials showed high AC conductivity and low dielectric constant. Diffuse reflectance studies were carried out for various dopant levels at 300 K by ultraviolet-visible (UV-Vis) spectroscopy. Considerable absorption of visible light by 0.5 wt.% and 1.0 wt.% Ag-TiO2 nanoparticles was observed due to the decrease of the energy band gap on Ag loading.

  9. Influence of temperature on AC conductivity of nanocrystalline CuAlO2

    NASA Astrophysics Data System (ADS)

    Prakash, T.

    2012-07-01

    Nanocrystalline CuAlO2 was synthesized by mechanical alloying of Cu2O and α-Al2O3 powders in the molar ratio of 1:1 for 20 h in toluene medium with tungsten carbide balls and vials using planetary ball mill. The ball milling was carried out at 300 rpm with a ball to powder weight ratio of 10:1 and then annealed at 1373 K in a platinum crucible for 20 h to get CuAlO2 phase with average crystallite size 45 nm. Complex impedance spectroscopic measurement in the frequency region 1 Hz to 10 MHz between the temperatures 333 to 473 K was carried out for nanocrystalline CuAlO2 sample. The obtained complex impedance data was analyzed for AC conductivities, DC and AC conductivities correlations and crossover frequencies ( f co ). The BNN (Barton, Nakajima and Namikawa) relation was applied to understand the correlation between DC and AC conductivities. The observed experimental results were discussed in the paper.

  10. Microwave a.c. conductivity of domain walls in ferroelectric thin films

    PubMed Central

    Tselev, Alexander; Yu, Pu; Cao, Ye; Dedon, Liv R.; Martin, Lane W.; Kalinin, Sergei V.; Maksymovych, Petro

    2016-01-01

    Ferroelectric domain walls are of great interest as elementary building blocks for future electronic devices due to their intrinsic few-nanometre width, multifunctional properties and field-controlled topology. To realize the electronic functions, domain walls are required to be electrically conducting and addressable non-destructively. However, these properties have been elusive because conducting walls have to be electrically charged, which makes them unstable and uncommon in ferroelectric materials. Here we reveal that spontaneous and recorded domain walls in thin films of lead zirconate and bismuth ferrite exhibit large conductance at microwave frequencies despite being insulating at d.c. We explain this effect by morphological roughening of the walls and local charges induced by disorder with the overall charge neutrality. a.c. conduction is immune to large contact resistance enabling completely non-destructive walls read-out. This demonstrates a technological potential for harnessing a.c. conduction for oxide electronics and other materials with poor d.c. conduction, particularly at the nanoscale. PMID:27240997

  11. Microwave a.c. conductivity of domain walls in ferroelectric thin films.

    PubMed

    Tselev, Alexander; Yu, Pu; Cao, Ye; Dedon, Liv R; Martin, Lane W; Kalinin, Sergei V; Maksymovych, Petro

    2016-05-31

    Ferroelectric domain walls are of great interest as elementary building blocks for future electronic devices due to their intrinsic few-nanometre width, multifunctional properties and field-controlled topology. To realize the electronic functions, domain walls are required to be electrically conducting and addressable non-destructively. However, these properties have been elusive because conducting walls have to be electrically charged, which makes them unstable and uncommon in ferroelectric materials. Here we reveal that spontaneous and recorded domain walls in thin films of lead zirconate and bismuth ferrite exhibit large conductance at microwave frequencies despite being insulating at d.c. We explain this effect by morphological roughening of the walls and local charges induced by disorder with the overall charge neutrality. a.c. conduction is immune to large contact resistance enabling completely non-destructive walls read-out. This demonstrates a technological potential for harnessing a.c. conduction for oxide electronics and other materials with poor d.c. conduction, particularly at the nanoscale.

  12. Microwave a.c. conductivity of domain walls in ferroelectric thin films

    SciTech Connect

    Tselev, Alexander; Yu, Pu; Cao, Ye; Dedon, Liv R.; Martin, Lane W.; Kalinin, Sergei V.; Maksymovych, Petro

    2016-05-31

    Ferroelectric domain walls are of great interest as elementary building blocks for future electronic devices due to their intrinsic few-nanometre width, multifunctional properties and field-controlled topology. To realize the electronic functions, domain walls are required to be electrically conducting and addressable non-destructively. However, these properties have been elusive because conducting walls have to be electrically charged, which makes them unstable and uncommon in ferroelectric materials. Here we reveal that spontaneous and recorded domain walls in thin films of lead zirconate and bismuth ferrite exhibit large conductance at microwave frequencies despite being insulating at d.c. We explain this effect by morphological roughening of the walls and local charges induced by disorder with the overall charge neutrality. a.c. conduction is immune to large contact resistance enabling completely non-destructive walls read-out. Finally, this demonstrates a technological potential for harnessing a.c. conduction for oxide electronics and other materials with poor d.c. conduction, particularly at the nanoscale.

  13. Microwave a.c. conductivity of domain walls in ferroelectric thin films

    DOE PAGES

    Tselev, Alexander; Yu, Pu; Cao, Ye; ...

    2016-05-31

    Ferroelectric domain walls are of great interest as elementary building blocks for future electronic devices due to their intrinsic few-nanometre width, multifunctional properties and field-controlled topology. To realize the electronic functions, domain walls are required to be electrically conducting and addressable non-destructively. However, these properties have been elusive because conducting walls have to be electrically charged, which makes them unstable and uncommon in ferroelectric materials. Here we reveal that spontaneous and recorded domain walls in thin films of lead zirconate and bismuth ferrite exhibit large conductance at microwave frequencies despite being insulating at d.c. We explain this effect by morphologicalmore » roughening of the walls and local charges induced by disorder with the overall charge neutrality. a.c. conduction is immune to large contact resistance enabling completely non-destructive walls read-out. Finally, this demonstrates a technological potential for harnessing a.c. conduction for oxide electronics and other materials with poor d.c. conduction, particularly at the nanoscale.« less

  14. Temperature and frequency dependence of AC conductivity of new quaternary Se-Te-Bi-Pb chalcogenide glasses

    NASA Astrophysics Data System (ADS)

    Yadav, Preeti; Sharma, Ambika

    2016-05-01

    The aim of the present work is to study the temperature and frequency dependence of ac conductivity of new quaternary Se84-xTe15Bi1.0Pbx chalcogenide glasses. The Se84-xTe15Bi1.0Pbx (x = 2, 6) glassy alloys are prepared by using melt quenching technique. The temperature and frequency dependent behavior of ac conductivity σac(ω) has been carried out in the frequency range 42 Hz to 5 MHz and in the temperature range of 298-323 K below glass transition temperature. The behavior of ac conductivity is described in terms of the power law ωs. The obtained temperature dependence behavior of ac conductivity and frequency component (s) are explained by means of correlated barrier hopping model recommended by Elliot.

  15. Random free energy barrier hopping model for ac conduction in chalcogenide glasses

    NASA Astrophysics Data System (ADS)

    Murti, Ram; Tripathi, S. K.; Goyal, Navdeep; Prakash, Satya

    2016-03-01

    The random free energy barrier hopping model is proposed to explain the ac conductivityac) of chalcogenide glasses. The Coulomb correlation is consistently accounted for in the polarizability and defect distribution functions and the relaxation time is augmented to include the overlapping of hopping particle wave functions. It is observed that ac and dc conduction in chalcogenides are due to same mechanism and Meyer-Neldel (MN) rule is the consequence of temperature dependence of hopping barriers. The exponential parameter s is calculated and it is found that s is subjected to sample preparation and measurement conditions and its value can be less than or greater than one. The calculated results for a - Se, As2S3, As2Se3 and As2Te3 are found in close agreement with the experimental data. The bipolaron and single polaron hopping contributions dominates at lower and higher temperatures respectively and in addition to high energy optical phonons, low energy optical and high energy acoustic phonons also contribute to the hopping process. The variations of hopping distance with temperature is also studied. The estimated defect number density and static barrier heights are compared with other existing calculations.

  16. Effect of nanosilica on optical, electric modulus and AC conductivity of polyvinyl alcohol/polyaniline films

    NASA Astrophysics Data System (ADS)

    El-Sayed, Somyia; Abel-Baset, Tarob; Elfadl, Azza Abou; Hassen, Arafa

    2015-05-01

    Nanosilica (NS) was synthesized by a sol-gel method and mixed with 0.98 polyvinyl alcohol (PVA)/0.02 polyaniline (PANI) in different amounts to produce nanocomposite films. High-resolution transmission electron microscopy (HR-TEM) revealed the average particle size of the NS to be ca. 15 nm. Scanning electron microscopy (SEM) showed that the NS was well-dispersed on the surface of the PVA/PNAI films. The Fourier transform infrared (FTIR) spectra of the samples showed a significant change in the intensity of the characteristic peak of the functional groups in the composite films with the amount of NS added. The absorbance and refractive index (n) of the composites were studied in the UV-vis range, and the optical energy band gap, Eg, and different optical parameters were calculated. The dielectric loss modulus, M″ and ac conductivity, σac, of the samples were studied within 300-425 K and 0.1 kHz-5 MHz, respectively. Two relaxation peaks were observed in the frequency dependence of the dielectric loss modulus, M″. The behavior of σac(f) for the composite films indicated that the conduction mechanism was correlated barrier hopping (CBH). The results of this work are discussed and compared with those of previous studies of similar composites.

  17. Temperature characterization of dielectric permittivity and AC conductivity of nano copper oxide-doped polyaniline composite

    NASA Astrophysics Data System (ADS)

    Shubha, L. N.; Madhusudana Rao, P.

    2016-06-01

    The polyaniline/copper oxide (PANI/CuO) nanocomposite was prepared by mixing solutions of polyaniline and copper oxide nanoparticles in dimethyl sulfoxide (DMSO). The synthesized polymer nanocomposites were characterized by X-ray powder diffraction (XRD), scanning electron microscope (SEM) and UV-visible spectroscopy. The characteristic peaks in XRD and UV-visible spectra confirmed the presence of CuO in the polymer structure. SEM images indicated morphological changes in the composite matrix as compared to the pristine PANI. The DC conductivity measurements were performed using two-probe method for various temperatures. AC conductivity and dielectric response of the composites were investigated in the frequency range of 102-106Hz using LCR meter. Dielectric permittivity ɛ‧(w) and dielectric loss factor ɛ‧‧(w) were investigated. It was observed that ɛ‧(w) and ɛ‧‧(w) decrease with increase in frequency at all temperatures. At a particular frequency it is observed that both ɛ‧(w) and ɛ‧‧(w) increase with increase in temperature. It was also observed that AC conductivity increased with increase in frequency and temperature.

  18. AC conductivity scaling behavior in grain and grain boundary response regime of fast lithium ionic conductors

    NASA Astrophysics Data System (ADS)

    Mariappan, C. R.

    2014-05-01

    AC conductivity spectra of Li-analogues NASICON-type Li1.5Al0.5Ge1.5P3O12 (LAGP), Li-Al-Ti-P-O (LATP) glass-ceramics and garnet-type Li7La2Ta2O13 (LLTO) ceramic are analyzed by universal power law and Summerfield scaling approaches. The activation energies and pre-exponential factors of total and grain conductivities are following the Meyer-Neldel (M-N) rule for NASICON-type materials. However, the garnet-type LLTO material deviates from the M-N rule line of NASICON-type materials. The frequency- and temperature-dependent conductivity spectra of LAGP and LLTO are superimposed by Summerfield scaling. The scaled conductivity curves of LATP are not superimposed at the grain boundary response region. The superimposed conductivity curves are observed at cross-over frequencies of grain boundary response region for LATP by incorporating the exp ( {{{ - (EAt - EAg )} {{{ - (EAt - EAg )} {kT}}} ) factor along with Summerfield scaling factors on the frequency axis, where EAt and EAg are the activation energies of total and grain conductivities, respectively.

  19. AC and DC conductivity of ionic liquid containing polyvinylidene fluoride thin films

    NASA Astrophysics Data System (ADS)

    Frübing, Peter; Wang, Feipeng; Kühle, Till-Friedrich; Gerhard, Reimund

    2016-01-01

    Polarisation processes and charge transport in polyvinylidene fluoride (PVDF) with a small amount (0.01-10 wt%) of the ionic liquid (IL) 1-ethyl-3-methylimidazolium nitrate ({[EMIM]}^+[{NO}_3]^-) are investigated by means of dielectric spectroscopy. The response of PVDF that contains more than 0.01 wt% IL is dominated by a low-frequency relaxation which shows typical signatures of electrode polarisation. Furthermore, the α a relaxation, related to the glass transition, disappears for IL contents of more than 1 wt%, which indicates that the amorphous phase loses its glass-forming properties and undergoes structural changes. The DC conductivity is determined from the low-frequency limit of the AC conductivity and from the dielectric loss peak related to the electrode polarisation. DC conductivities of 10^{-10} to 10^{-2} {S}/{m} are obtained—increasing with IL content and temperature. The dependence of the DC conductivity on the IL content follows a power law with an exponent greater than one, indicating an increase in the ion mobility. The temperature dependence of the DC conductivity shows Vogel-Fulcher-Tammann behaviour, which implies that charge transport is coupled to polymer chain motion. Mobile ion densities and ion mobilities are calculated from the DC conductivity and the dielectric loss related to electrode polarisation, with the results that less than one per cent of the total ion concentration contributes to the conductivity and that the strong increase in conductivity with temperature is mainly caused by a strong increase in ion mobility. This leads to the conclusion that in particular the ion mobility must be reduced in order to decrease the DC conductivity.

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

    NASA Astrophysics Data System (ADS)

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

    2016-07-01

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

  1. Floquet spectrum and driven conductance in Dirac materials: Effects of Landau-Zener-Stückelberg-Majorana interferometry

    NASA Astrophysics Data System (ADS)

    Rodionov, Ya. I.; Kugel, K. I.; Nori, Franco

    2016-11-01

    Using the Landau-Zener-Stückelberg-Majorana-type (LZSM) semiclassical approach, we study both graphene and a thin film of a Weyl semimetal subjected to a strong ac electromagnetic field. The spectrum of quasienergies in the Weyl semimetal turns out to be similar to that of a graphene sheet. It has been predicted qualitatively that the transport properties of strongly irradiated graphene oscillate as a function of the radiation intensity [S. V. Syzranov et al., Phys. Rev. B 88, 241112 (2013)], 10.1103/PhysRevB.88.241112. Here we obtain rigorous quantitative results for a driven linear conductance of graphene and a thin film of a Weyl semimetal. The exact quantitative structure of oscillations exhibits two contributions. The first one is a manifestation of the Ramsauer-Townsend effect, while the second contribution is a consequence of the LZSM interference defining the spectrum of quasienergies.

  2. Electric properties of carbon nano-onion/polyaniline composites: a combined electric modulus and ac conductivity study

    NASA Astrophysics Data System (ADS)

    Papathanassiou, Anthony N.; Mykhailiv, Olena; Echegoyen, Luis; Sakellis, Ilias; Plonska-Brzezinska, Marta E.

    2016-07-01

    The complex electric modulus and the ac conductivity of carbon nano-onion/polyaniline composites were studied from 1 mHz to 1 MHz at isothermal conditions ranging from 15 K to room temperature. The temperature dependence of the electric modulus and the dc conductivity analyses indicate a couple of hopping mechanisms. The distinction between thermally activated processes and the determination of cross-over temperature were achieved by exploring the temperature dependence of the fractional exponent of the dispersive ac conductivity and the bifurcation of the scaled ac conductivity isotherms. The results are analyzed by combining the granular metal model (inter-grain charge tunneling of extended electron states located within mesoscopic highly conducting polyaniline grains) and a 3D Mott variable range hopping model (phonon assisted tunneling within the carbon nano-onions and clusters).

  3. AC conductivity and structural properties of Mg-doped ZnO ceramic

    NASA Astrophysics Data System (ADS)

    Othman, Zayani Jaafar; Hafef, Olfa; Matoussi, Adel; Rossi, Francesca; Salviati, Giancarlo

    2015-11-01

    Undoped ZnO and Zn1- x Mg x O ceramic pellets were synthesized by the standard sintering method at the temperature of 1200 °C. The influence of Mg doping on the morphological, structural and electrical properties was studied. The scanning electron microscopy images revealed rough surface textured by grain boundaries and compacted grains having different shapes and sizes. Indeed, the X-ray diffraction reveals the alloying of hexagonal ZnMgO phase and the segregation of cubic MgO phase. The crystallite size, strain and stress were studied using Williamson-Hall (W-H) method. The results of mean particle size of Zn1- x Mg x O composites showed an inter-correlation with W-H analysis and Sherrer method. The electrical conductivity of the films was measured from 173 to 373 K in the frequency range of 0.1 Hz-1 MHz to identify the dominant conductivity mechanism. The DC conductivity is thermally activated by electron traps having activation energy of about 0.09 to 0.8 eV. The mechanisms of AC conductivity are controlled by the correlated barrier hopping model for the ZnO sample and the small polaron tunneling (SPT) model for Zn0.64Mg0.36O and Zn0.60Mg0.40O composites.

  4. Synthesis, Spectroscopic, ac Conductivity and Thermal Studies on Co(III) Acetylacetonate-Iodine Complex

    NASA Astrophysics Data System (ADS)

    Hashem, H. A.; Refat, M. S.

    A spectrophotometric study of 1:1 donor-acceptor complex, cobalt (III) acetylacetonate (donor) and iodine (σ-acceptor) has been preformed. The equilibrium constants, (K) and the absorpitivity (ɛ) for the formation of the iodine complex have been calculated. The predicted structure of the solid triiodide charge-transfer complex reported in this study is further supported by thermal, far and mid infrared spectroscopic measurements. Electron transfer from Co (acac = 2, 4-pentanedionate)3 to iodine leads to the formation of an organic semiconductor with the formula of [Co(acac)3]_2 I+. I3-. The kinetic parameters (nonisothermal method) for their decomposition have been evaluated by graphical methods using the equations of Freeman-Carroll (FC), Horowitz-Metzger (HM) and Coats-Redfern (CR). The ac conductivity and dielectric properties of [Co(acac)3]_2 I+. I3- have been measured over the frequency 50-106 Hz at temperature 298 K.

  5. Phonon effects on the current noise spectra and the ac conductance of a single molecular junction.

    PubMed

    Ding, Guo-Hui; Dong, Bing

    2014-07-30

    By using nonequilibrium Green's functions and the equation of motion method, we formulate a self-consistent field theory for the electron transport through a single-molecule junction (SMJ) coupled with a vibrational mode. We show that the nonequilibrium dynamics of the phonons in a strong electron-phonon coupling regime can be taken into account appropriately in this self-consistent perturbation theory, and the self-energy of the phonons is connected with the current fluctuations in the molecular junction. We calculate the finite-frequency nonsymmetrized noise spectra and the ac conductance, which reveal a wealth of inelastic electron tunneling characteristics on the absorption and emission properties of this SMJ. In the presence of a finite bias voltage and the electron tunneling current, the vibration mode of the molecular junction is heated and driven to an unequilibrated state. The influences of unequilibrated phonons on the current and the noise spectra are investigated.

  6. Phonon effects on the current noise spectra and the ac conductance of a single molecular junction

    NASA Astrophysics Data System (ADS)

    Ding, Guo-Hui; Dong, Bing

    2014-07-01

    By using nonequilibrium Green’s functions and the equation of motion method, we formulate a self-consistent field theory for the electron transport through a single-molecule junction (SMJ) coupled with a vibrational mode. We show that the nonequilibrium dynamics of the phonons in a strong electron-phonon coupling regime can be taken into account appropriately in this self-consistent perturbation theory, and the self-energy of the phonons is connected with the current fluctuations in the molecular junction. We calculate the finite-frequency nonsymmetrized noise spectra and the ac conductance, which reveal a wealth of inelastic electron tunneling characteristics on the absorption and emission properties of this SMJ. In the presence of a finite bias voltage and the electron tunneling current, the vibration mode of the molecular junction is heated and driven to an unequilibrated state. The influences of unequilibrated phonons on the current and the noise spectra are investigated.

  7. Ionic ac and dc conductivities of NaCrP2O7 compound

    NASA Astrophysics Data System (ADS)

    Sassi, M.; Oueslati, A.; Gargouri, M.

    2015-05-01

    The NaCrP2O7 compound was prepared by the solid-state reaction method. The formation of a single-phase material was confirmed by the X-ray diffraction studies and found to be a monoclinic system. The electrical properties of this compound have been measured in the temperature range from 523 to 673 K and the frequency range from 209 Hz to 5 MHz. The Nyquist plots are well fitted to an equivalent circuit consisting of a series of combination of grains and grain boundary elements. The ac conductivity of NaCrP2O7 has been analyzed as a function of temperature and frequency. The scaling behavior of the imaginary part of the complex modulus suggests that the relaxation describes the same mechanism at various temperatures. The conductivity and modulus formalisms provide nearly the same activation energies for electrical relaxation of mobile ions suggesting that the ion transport is probably due to a hopping mechanism dominated by the motion of the monovalent ions Na+ along tunnels presented in the structure of the investigated material.

  8. Anomalous dielectric and AC conductivity behavior of the nanocrystalline Ni-Cu ferrite synthesized via combustion method

    SciTech Connect

    Madhu, B. J.; Rashmi, B. N.; Banu, Arshiya; Seema, G. A.; Shruthi, B.; Jayanna, H. S.

    2013-02-05

    Nanocrystalline Ni-Cu ferrites (Ni{sub 0.5}Cu{sub 0.5}Fe{sub 2}O{sub 4}) were prepared using solution combustion method. The structure of the samples were studied with the X-ray diffraction (XRD) using Cu-K{sub {alpha}} radiation. Frequency and temperature dependence of dielectric and a.c. conductivity studies have been undertaken on the Ni-Cu nanoferrites in the frequency region 100Hz-5MHz. The dielectric constant ({epsilon} Prime ) is found to decrease initially with the frequency and finally reaching a constant value at higher frequencies. Observed trends in the dielectric constant are ascribed to the Maxwell-Wagner type interfacial polarization, which is in agreement with the Koop'fs phenomenological theory. The a.c. conductivity ({sigma}{sub ac}) is found to increase with an increase in the frequency from room temperature up to 300 Degree-Sign C. However, at a temperature of 400 Degree-Sign C, the a.c. conductivity is found to decrease with an increase in the frequency exhibiting an abnormal behavior. The electrical conduction mechanism in the present nano nickel-copper ferrite is found to be in accordance with the electron hopping model.

  9. Anomalous dielectric and AC conductivity behavior of the nanocrystalline Ni-Cu ferrite synthesized via combustion method

    NASA Astrophysics Data System (ADS)

    Madhu, B. J.; Rashmi, B. N.; Banu, Arshiya; Seema, G. A.; Shruthi, B.; Jayanna, H. S.

    2013-02-01

    Nanocrystalline Ni-Cu ferrites (Ni0.5Cu0.5Fe2O4) were prepared using solution combustion method. The structure of the samples were studied with the X-ray diffraction (XRD) using Cu-Kα radiation. Frequency and temperature dependence of dielectric and a.c. conductivity studies have been undertaken on the Ni-Cu nanoferrites in the frequency region 100Hz-5MHz. The dielectric constant (ɛ') is found to decrease initially with the frequency and finally reaching a constant value at higher frequencies. Observed trends in the dielectric constant are ascribed to the Maxwell-Wagner type interfacial polarization, which is in agreement with the Koop'fs phenomenological theory. The a.c. conductivityac) is found to increase with an increase in the frequency from room temperature up to 300 °C. However, at a temperature of 400 °C, the a.c. conductivity is found to decrease with an increase in the frequency exhibiting an abnormal behavior. The electrical conduction mechanism in the present nano nickel-copper ferrite is found to be in accordance with the electron hopping model.

  10. A.c. conductivity and dielectric properties of LiNi 3/5Cu 2/5VO 4 ceramics

    NASA Astrophysics Data System (ADS)

    Ram, Moti

    2010-03-01

    The LiNi 3/5Cu 2/5VO 4 was synthesized using solution-based chemical method whose dielectric and a.c. conductivity properties were investigated using complex impedance spectroscopy (CIS) technique. Variation of dielectric constant ( εr) as a function of frequency at different temperatures indicates low frequency dispersion. A.c conductivity analysis indicates that electrical conduction in the material is a thermally activated process. Frequency dependence of a.c. conductivity at different temperatures obeys Jonscher's universal law: σ ac= σ dc+ A( ω) n.

  11. Studies on the activation energy from the ac conductivity measurements of rubber ferrite composites containing manganese zinc ferrite

    NASA Astrophysics Data System (ADS)

    Hashim, Mohd.; Alimuddin; Kumar, Shalendra; Shirsath, Sagar E.; Mohammed, E. M.; Chung, Hanshik; Kumar, Ravi

    2012-11-01

    Manganese zinc ferrites (MZF) have resistivities between 0.01 and 10 Ω m. Making composite materials of ferrites with either natural rubber or plastics will modify the electrical properties of ferrites. The moldability and flexibility of these composites find wide use in industrial and other scientific applications. Mixed ferrites belonging to the series Mn(1-x)ZnxFe2O4 were synthesized for different ‘x’ values in steps of 0.2, and incorporated in natural rubber matrix (RFC). From the dielectric measurements of the ceramic manganese zinc ferrite and rubber ferrite composites, ac conductivity and activation energy were evaluated. A program was developed with the aid of the LabVIEW package to automate the measurements. The ac conductivity of RFC was then correlated with that of the magnetic filler and matrix by a mixture equation which helps to tailor properties of these composites.

  12. The change in dielectric constant, AC conductivity and optical band gaps of polymer electrolyte film: Gamma irradiation

    SciTech Connect

    Raghu, S. Subramanya, K. Sharanappa, C. Mini, V. Archana, K. Sanjeev, Ganesh Devendrappa, H.

    2014-04-24

    The effects of gamma (γ) irradiation on dielectric and optical properties of polymer electrolyte film were investigated. The dielectric constant and ac conductivity increases with γ dose. Also optical band gap decreased from 4.23 to 3.78ev after irradiation. A large dependence of the polymer properties on the irradiation dose was noticed. This suggests that there is a possibility of improving polymer electrolyte properties on gamma irradiation.

  13. AC CONDUCTION PHENOMENON OF Li2O-WO3-B2O3 GLASSES DOPED WITH V2O5

    NASA Astrophysics Data System (ADS)

    Rao, Linganaboina Srinivasa; Veeraiah, Nalluri; Rao, Tumu Venkatappa

    2013-04-01

    The glass composition 40Li2O-5WO3-(55-x)B2O3: xV2O5 for x = 0.2, 0.4, 0.6 and 0.8 is chosen for the present study. The glass samples were synthesized by conventional melt-quenching technique. The dielectric properties such as constant (ɛ‧), loss (tan δ) and ac conductivityac) are carried out as a function of temperature (30-270°C) and frequency (102-105 Hz). The glass sample (at x = 0.6) exhibited highest ac conductivityac) and spreading factor (β) among all the samples. All glasses exhibited mixed conduction (both electronic and ionic) at high temperatures. The frequency exponent s denotes the ac conduction mechanism is associated with both QMT model (at low temperatures) and CBH model (at high temperatures).

  14. Gas sensing properties of magnesium doped SnO{sub 2} thin films in relation to AC conduction

    SciTech Connect

    Deepa, S.; Skariah, Benoy Thomas, Boben; Joseph, Anisha

    2014-01-28

    Conducting magnesium doped (0 to 1.5 wt %) tin oxide thin films prepared by Spray Pyrolysis technique achieved detection of 1000 ppm of LPG. The films deposited at 304 °C exhibit an enhanced response at an operating temperature of 350 °C. The microstructural properties are studied by means of X-ray diffraction. AC conductivity measurements are carried out using precision LCR meter to analyze the parameters that affect the variation in sensing. The results are correlated with compositional parameters and the subsequent modification in the charge transport mechanism facilitating an enhanced LPG sensing action.

  15. Gas sensing properties of magnesium doped SnO2 thin films in relation to AC conduction

    NASA Astrophysics Data System (ADS)

    Deepa, S.; Joseph, Anisha; Skariah, Benoy; Thomas, Boben

    2014-01-01

    Conducting magnesium doped (0 to 1.5 wt %) tin oxide thin films prepared by Spray Pyrolysis technique achieved detection of 1000 ppm of LPG. The films deposited at 304 °C exhibit an enhanced response at an operating temperature of 350 °C. The microstructural properties are studied by means of X-ray diffraction. AC conductivity measurements are carried out using precision LCR meter to analyze the parameters that affect the variation in sensing. The results are correlated with compositional parameters and the subsequent modification in the charge transport mechanism facilitating an enhanced LPG sensing action.

  16. A.C. Conductivity of Bi2Cu0.1V0.9O5.35 Films for Fuel Cell Application

    NASA Astrophysics Data System (ADS)

    Nimat, R. K.; Lokare, S. A.; Pawar, S. H.

    2011-07-01

    The A.C. conductivity and dielectric properties of Bi2Cu0.1V0.9O5.35 thin films were studied as a function of frequency and temperature. The A.C. conductivity of Bi2Cu0.1V0.9O5.35 film increases with frequency. The low frequency region corresponds to the D.C. conductivity where the inter-well hopping responsible for D.C. conduction completely dominates over the intra-well hopping associated with pure A.C. conduction. Higher values of A.C. conductivity for films formed on alumina substrates predict their suitability for fuel cell application

  17. Calculation of the ac to dc resistance ratio of conductive nonmagnetic straight conductors by applying FEM simulations

    NASA Astrophysics Data System (ADS)

    Riba, Jordi-Roger

    2015-09-01

    This paper analyzes the skin and proximity effects in different conductive nonmagnetic straight conductor configurations subjected to applied alternating currents and voltages. These effects have important consequences, including a rise of the ac resistance, which in turn increases power loss, thus limiting the rating for the conductor. Alternating current (ac) resistance is important in power conductors and bus bars for line frequency applications, as well as in smaller conductors for high frequency applications. Despite the importance of this topic, it is not usually analyzed in detail in undergraduate and even in graduate studies. To address this, this paper compares the results provided by available exact formulas for simple geometries with those obtained by means of two-dimensional finite element method (FEM) simulations and experimental results. The paper also shows that FEM results are very accurate and more general than those provided by the formulas, since FEM models can be applied in a wide range of electrical frequencies and configurations.

  18. Motor, Emotional, and Cognitive Empathy in Children and Adolescents with Autism Spectrum Disorder and Conduct Disorder

    ERIC Educational Resources Information Center

    Bons, Danielle; van den Broek, Egon; Scheepers, Floor; Herpers, Pierre; Rommelse, Nanda; Buitelaaar, Jan K.

    2013-01-01

    It is unclear which aspects of empathy are shared and which are uniquely affected in autism spectrum disorder (ASD) and conduct disorder (CD) as are the neurobiological correlates of these empathy impairments. The aim of this systematic review is to describe the overlap and specificity of motor, emotional, and cognitive aspects of empathy in…

  19. AC magnetic field-assisted method to develop porous carbon nanotube/conducting polymer composites for application in thermoelectric materials

    NASA Astrophysics Data System (ADS)

    Chuang, Chun-Yu; Yang, Shu-Chian; Chang, Su-Hua; Yang, Ta-I.

    2015-04-01

    Thermoelectric materials are very effective in converting waste heat sources into useful electricity. Researchers are continuing to develop new polymeric thermoelectric materials. The segregated-network carbon nanotube (CNT)- polymer composites are most promising. Thus, the goal of this study is to develop novel porous CNT -polymer composites with improved thermoelectric properties. The research efforts focused on modifying the surface of the CNT with magnetic nanoparticles so that heat was released when subjecting to an AC magnetic field. Subsequently, polymers covered on the surface of the CNT were crosslinked. The porous CNT -polymer composites can be obtained by removing the un-crosslinked polymers. Polydimethylsiloxane polymer was utilized to investigate the effect of porosity and electrical conductivity on the thermoelectric properties of the composites. This AC magnetic field-assisted method to develop porous carbon nanotube/polymer composites for application in thermoelectric materials is introduced for the first time. The advantage of this method is that the electrical conductivity of the composites was high since we can easily to manipulate the CNT to form a conducting path. Another advantage is that the high porosity significantly reduced the thermal conductivity of the composites. These two advantages enable us to realize the polymer composites for thermoelectric applications. We are confident that this research will open a new avenue for developing polymer thermoelectric materials.

  20. Dielectric relaxation and ac conductivity behavior of carboxyl functionalized multiwalled carbon nanotubes/poly (vinyl alcohol) composites

    NASA Astrophysics Data System (ADS)

    Amrin, Sayed; Deshpande, V. D.

    2017-03-01

    We study the dielectric relaxation and ac conductivity behavior of MWCNT-COOH/Polyvinyl alcohol nanocomposite films in the temperature (T) range 303-423 K and in the frequency (f) range 0.1 Hz-1 MHz. The dielectric constant increases with an increase in temperature and also with an increase in MWCNT-COOH loading into the polymer matrix, as a result of interfacial polarization. The permittivity data were found to fit well with the modified Cole-Cole equation. Temperature dependent values of the relaxation times, free charge carrier conductivity and space charge carrier conductivity were extracted from the equation. An observed increment in the ac conductivity for the nanocomposites was analysed by a Jonscher power law which suggests that the correlated barrier hopping is the dominant charge transport mechanism for the nanocomposite films. The electric modulus study revealed deviations from ideal Debye-type behavior which are explained by considering a generalized susceptibility function. XRD and DSC results show an increase in the degree of crystallinity.

  1. Development of the Exams Data Analysis Spreadsheet as a Tool to Help Instructors Conduct Customizable Analyses of Student ACS Exam Data

    ERIC Educational Resources Information Center

    Brandriet, Alexandra; Holme, Thomas

    2015-01-01

    The American Chemical Society Examinations Institute (ACS-EI) has recently developed the Exams Data Analysis Spread (EDAS) as a tool to help instructors conduct customizable analyses of their student data from ACS exams. The EDAS calculations allow instructors to analyze their students' performances both at the total score and individual item…

  2. Anomalous three-dimensional bulk ac conduction within the Kondo gap of SmB6 single crystals

    NASA Astrophysics Data System (ADS)

    Laurita, N. J.; Morris, C. M.; Koohpayeh, S. M.; Rosa, P. F. S.; Phelan, W. A.; Fisk, Z.; McQueen, T. M.; Armitage, N. P.

    2016-10-01

    The Kondo insulator SmB6 has long been known to display anomalous transport behavior at low temperatures, T <5 K. In this temperatures range, a plateau is observed in the dc resistivity, contrary to the exponential divergence expected for a gapped system. Recent theoretical calculations suggest that SmB6 may be the first topological Kondo insulator (TKI) and propose that the residual conductivity is due to topological surface states which reside within the Kondo gap. Since the TKI prediction many experiments have claimed to observe high mobility surface states within a perfectly insulating hybridization gap. Here, we investigate the low energy optical conductivity within the hybridization gap of single crystals of SmB6 via time domain terahertz spectroscopy. Samples grown by both optical floating zone and aluminum flux methods are investigated to probe for differences originating from sample growth techniques. We find that both samples display significant three-dimensional bulk conduction originating within the Kondo gap. Although SmB6 may be a bulk dc insulator, it shows significant bulk ac conduction that is many orders of magnitude larger than any known impurity band conduction. The nature of these in-gap states and their coupling with the low energy spin excitons of SmB6 is discussed. Additionally, the well-defined conduction path geometry of our optical experiments allows us to show that any surface states, which lie below our detection threshold if present, must have a sheet resistance of R /square≥ 1000 Ω .

  3. Dielectric and ac conductivity studies of ZnO/Eu3+: Titanosilicate matrix

    NASA Astrophysics Data System (ADS)

    Arun Kumar, K. V.; Sunil, Thomas; Ann Mary, K. A.; Cyriac, Joseph; Biju, P. R.; Unnikrishnan, N. V.

    2014-01-01

    ZnO nanoparticles /Eu3+ doped SiO2-TiO2 matrices were synthesized through sol-gel route. Structural and dielectric properties of ZnO nanocrystallites co-doped with Eu3+ in SiO2-TiO2 matrices were presented. The HRTEM and XRD measurements confirm the presence of ZnO nanocrystallites. The dielectric and electrical conductivity studies of the samples are completed for a frequency of 100 Hz to 2 MHz. The conductivity variation with the ZnO content in the Eu3+ doped SiO2-TiO2 system were explained by correlating the presence of ionic contribution to the electrical conductivity process. From the frequency dependence of dielectric constant and conductivity, the Cole-Cole parameters and power law parameters were evaluated. The dielectric relaxation phenomena were investigated using the dielectric moduli formulation.

  4. AC conductivity of (FeCoZr)x(PZT)(100-x) nanocomposites produced in vacuum chamber

    NASA Astrophysics Data System (ADS)

    Boiko, Oleksandr; Bondariev, Vitalii; Czarnacka, Karolina

    2015-09-01

    In this work, the temperature and frequency dependences of conductivity σ and Arrhenius plots of annealed nanocomposite films containing Fe45Co45Zr10 - based nanoparticles embedded in a doped PbZrTiO3 ferroelectric matrix were studied. The nanocomposites studied were deposited by sputtering with use of argon and oxygen ions in a vacuum chamber. Tested samples were followed by a 15-min annealing process in air in the temperature range of 398 K <= Ta <= 748 K with steps of 25 K. The σ(f,T) dependences of nanocomposite samples was measured in ambient temperature range of 77 K < Tp < 373 K at frequencies of 50 Hz < f < 1MHz. It was established that nanocomposite sample with metallic phase content x = 55.6 at.% demonstrates strong temperature and frequency dependences, which is typical for a percolation systems. Type of conduction in such nanostructure is defined as dielectric, which may be related with the additional oxidation of metallic nanoparticles during the annealing process. For the tested sample with x = 88.4 at.%. we observe metallic type of conduction, when metallic nanoparticles form a permanent conductive channels in dielectric matrix.

  5. AC conductivity and electrochemical studies of PVA/PEG based polymer blend electrolyte films

    NASA Astrophysics Data System (ADS)

    Polu, Anji Reddy; Kumar, Ranveer; Dehariya, Harsha

    2012-06-01

    Polymer blend electrolyte films based on Polyvinyl alcohol(PVA)/Poly(ethylene glycol)(PEG) and magnesium nitrate (Mg(NO3)2) were prepared by solution casting technique. Conductivity in the temperature range 303-373 K and transference number measurements have been employed to investigate the charge transport in this polymer blend electrolyte system. The highest conductivity is found to be 9.63 × 10-5 S/cm at 30°C for sample with 30 weight percent of Mg(NO3)2 in PVA/PEG blend matrix. Transport number data shows that the charge transport in this polymer electrolyte system is predominantly due to ions. Using this electrolyte, an electrochemical cell with configuration Mg/(PVA+PEG+Mg(NO3)2)/(I2+C+electrolyte) was fabricated and its discharge characteristics profile has been studied.

  6. Effects of Luttinger leads on the AC conductance of a quantum dot

    NASA Astrophysics Data System (ADS)

    Yang, Kai-Hua; Qin, Chang-Dong; Wang, Huai-Yu; Liu, Kai-Di

    2017-04-01

    We investigate the joint effects of the intralead electron interaction and an external alternating gate voltage on the transport of a quantum dot coupled to two Luttinger liquid leads in the Kondo regime. We find the transferring between two Kondo physics mechanics by investigation of differential conductance. For very weak intralead interaction, the satellite and main Kondo resonant peaks appear in the differential conductance. For moderately strong intralead interaction, all the peaks disappear and evolve into dips, which signifies that a photon-assisted single-channel Kondo (1CK) physics turns into two-channel Kondo (2CK) physics. The 1CK and 2CK mechanisms can coexist within a region of the intralead interaction parameter. The 1CK physics transits to the 2CK one gradually, not suddenly. In the limit of strong interaction, all dips disappear. When the bias voltage is small, there is no photon exchange between the quantum dot and alternative field, and the differential conductance scales as a power law both in bias voltage and in temperature. As the field becomes stronger, the quantum dot will emit and absorb photons.

  7. Estimation of Density of Localized States in Amorphous Se80Te20 and Se80Te10M10 (M = Cd, In, Sb) Alloys Using AC Conductivity Measurements

    NASA Astrophysics Data System (ADS)

    Chandel, N.; Mehta, N.; Kumar, A.

    2015-08-01

    The ac conductivity of amorphous Se80Te20 (a-Se80Te20) and amorphous Se80Te10M10 (a-Se80Te10M10) alloys has been measured as a function of temperature and frequency in a low-temperature regime. An analysis of the experimental data confirms that ac conductivity is reasonably well interpreted by the Austin-Mott model. The density of localized states was determined in the low-temperature region from 201 K to 280 K. Possible explanations of "metal-induced effects" on the conduction mechanism of a-Se80Te20 alloy are discussed.

  8. AC Hopping Conductance in Nanocomposite Films with Ferromagnetic Alloy Nanoparticles in a PbZrTiO3 Matrix

    NASA Astrophysics Data System (ADS)

    Koltunowicz, T. N.; Zukowski, P.; Boiko, O.; Saad, A.; Fedotova, J. A.; Fedotov, A. K.; Larkin, A. V.; Kasiuk, J.

    2015-07-01

    In this work, the temperature and frequency dependences of the real part of the admittance [ σ( f, T)] of annealed nanocomposite films containing Co45 Fe45Zr10-based nanoparticles covered with native oxides and embedded in a doped PbZrTiO3 ferroelectric matrix were studied. The nanocomposites studied were deposited by ion sputtering a complex target in a mixed Ar/O2 atmosphere followed by a 15-min annealing process (with steps of 25 K) in air in the temperature range of 398 K ≤ T a ≤ 573 K. The σ( f, T) of the annealed samples was measured in the temperature range of 77 K < T p < 373 K at frequencies of 50 Hz < f < 1 MHz. The observed σ( f, T) dependences confirmed that the annealed samples displayed the effects of negative capacitance over the whole frequency and temperature ranges studied because of the pronounced oxidation of the nanoparticles. The σ( f, T) dependences obtained are described using an earlier-developed AC hopping conductance model. Comparisons between experimental and simulation results allow the model parameters to be estimated, such as the activation energies of the hopping conductance and the lifetimes of the electrons in the nanoparticles.

  9. A single-shot spatial chirp method for measuring initial AC conductivity evolution of femtosecond laser pulse excited warm dense matter

    SciTech Connect

    Chen, Z.; Hering, P.; Brown, S. B.; Curry, C.; Tsui, Y. Y.; Glenzer, S. H.

    2016-09-19

    To study the rapid evolution of AC conductivity from ultrafast laser excited warm dense matter (WDM), a spatial chirp single-shot method is developed utilizing a crossing angle pump-probe configuration. The pump beam is shaped individually in two spatial dimensions so that it can provide both sufficient laser intensity to excite the material to warm dense matter state and a uniform time window of up to 1 ps with sub-100 fs FWHM temporal resolution. Here, temporal evolution of AC conductivity in laser excited warm dense gold was also measured.

  10. A single-shot spatial chirp method for measuring initial AC conductivity evolution of femtosecond laser pulse excited warm dense matter.

    PubMed

    Chen, Z; Hering, P; Brown, S B; Curry, C; Tsui, Y Y; Glenzer, S H

    2016-11-01

    To study the rapid evolution of AC conductivity from ultrafast laser excited warm dense matter (WDM), a spatial chirp single-shot method is developed utilizing a crossing angle pump-probe configuration. The pump beam is shaped individually in two spatial dimensions so that it can provide both sufficient laser intensity to excite the material to warm dense matter state and a uniform time window of up to 1 ps with sub-100 fs FWHM temporal resolution. Temporal evolution of AC conductivity in laser excited warm dense gold was also measured.

  11. Relating the disease mutation spectrum to the evolution of the cystic fibrosis transmembrane conductance regulator (CFTR).

    PubMed

    Rishishwar, Lavanya; Varghese, Neha; Tyagi, Eishita; Harvey, Stephen C; Jordan, I King; McCarty, Nael A

    2012-01-01

    Cystic fibrosis (CF) is the most common genetic disease among Caucasians, and accordingly the cystic fibrosis transmembrane conductance regulator (CFTR) protein has perhaps the best characterized disease mutation spectrum with more than 1,500 causative mutations having been identified. In this study, we took advantage of that wealth of mutational information in an effort to relate site-specific evolutionary parameters with the propensity and severity of CFTR disease-causing mutations. To do this, we devised a scoring scheme for known CFTR disease-causing mutations based on the Grantham amino acid chemical difference matrix. CFTR site-specific evolutionary constraint values were then computed for seven different evolutionary metrics across a range of increasing evolutionary depths. The CFTR mutational scores and the various site-specific evolutionary constraint values were compared in order to evaluate which evolutionary measures best reflect the disease-causing mutation spectrum. Site-specific evolutionary constraint values from the widely used comparative method PolyPhen2 show the best correlation with the CFTR mutation score spectrum, whereas more straightforward conservation based measures (ConSurf and ScoreCons) show the greatest ability to predict individual CFTR disease-causing mutations. While far greater than could be expected by chance alone, the fraction of the variability in mutation scores explained by the PolyPhen2 metric (3.6%), along with the best set of paired sensitivity (58%) and specificity (60%) values for the prediction of disease-causing residues, were marginal. These data indicate that evolutionary constraint levels are informative but far from determinant with respect to disease-causing mutations in CFTR. Nevertheless, this work shows that, when combined with additional lines of evidence, information on site-specific evolutionary conservation can and should be used to guide site-directed mutagenesis experiments by more narrowly defining the

  12. Influence of n-type nickel ferrite in enhancing the AC conductivity of optimized polyaniline-nickel ferrite nanocomposite

    NASA Astrophysics Data System (ADS)

    Megha, R.; Ravikiran, Y. T.; Vijaya Kumari, S. C.; Thomas, S.

    2017-04-01

    In the present work, n-type nickel ferrite (NF) particles prepared by sol gel autocombustion method were used to synthesize optimized polyaniline-nickel ferrite (PANI-NF) nanocomposite by in situ polymerization method. Then, NF, PANI and the composite were structurally characterized using Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques. Improved π-electron delocalization in PANI-NF composite as compared to that in PANI was confirmed from FTIR analysis. Interfacial interaction between PANI and NF was confirmed from XRD studies. Highly agglomerated, more densely packed particles of the composite facilitating easier charge transport were confirmed from SEM image. Transmission electron microscopy (TEM) image was analysed to calculate accurate average particle size of the composite by fitting the data to log-normal distribution function. Crystalline nature of the composite was confirmed from selected area electron diffraction (SAED) analysis. Remarkable increase in AC conductivity of the PANI-NF composite as compared to that of PANI due mainly to the formation of interfacial heterojunction barrier between p-type PANI and n-type NF was confirmed experimentally and well supported theoretically by calculating binding energy, hopping distance and density of states at Fermi level as per correlated barrier hopping (CBH) model.

  13. AC conductivity and its scaling behavior in MgO-Li2O-B2O3-Bi2O3 glasses

    NASA Astrophysics Data System (ADS)

    Purnima, M.; Bale, Shashidhar; Samee, M. A.; Ahmmad, Shaik Kareem; Rahman, Syed

    2013-02-01

    In the present work, the compositional dependence of density, refractive index and glass transition temperature of xMgO-(25-x)Li2O-50B2O3-25Bi2O3 glasses is studied. Impedance spectroscopy technique is employed on these samples and the data are analyzed using Cole-Cole type impedance response function. The AC conductivity behavior of the present glasses has been investigated in the frequency range from 100 Hz to 1 MHz and as a function of temperature the measured AC data are analyzed using the Jonscher’s universal power law to explain the observed dispersive behavior of the electrical conductivity. The temperature and composition dependence scaling behavior in the AC conductivity are satisfactorily explained by scaling the AC conductivity σ‧(ω) by hopping frequency ωp. The frequency response of dielectric constant ɛ‧ and dielectric loss tanδ as a function of temperature were studied. The tanδ peak shifts to higher frequency with increasing temperature, indicating dipolar relaxation character of dielectric loss in the present glasses.

  14. ac conduction in disordered solids: Comparison of effective-medium and distributed-transition-rate-response models

    NASA Astrophysics Data System (ADS)

    MacDonald, J. Ross

    1994-04-01

    Dyre has proposed that in the low-temperature limit an effective medium approximation, termed the Bryksin equation here (the BEM), predicts a universal frequency dependence for the normalized small-signal ac frequency relaxation response of nonmetallic disordered solids. This response has been claimed to be practically identical to that found for an exponential distribution of transition rates (EDTR) in the particular limiting uniform-energy-barrier-distribution case, but comparison of the two responses has been inadequate so far. Although it is shown here that they can be well differentiated, the question of which or either is universal still requires further comparisons with experiment for its answer. A generalization of the limiting low-temperature BEM equation applicable for nonzero temperatures, the GBEM, is developed and used to evaluate the temperature and frequency ranges for which the BEM is still adequate. It is found that GBEM response can be well approximated by the important EDTR solution and leads to a frequency exponent with the same temperature dependence as the latter. An expression derived herein for the dc conductivity predicted by the GBEM involves 1/3 of the maximum thermal activation energy (i.e., the effective percolation energy), however, rather than the energy itself. Further, unlike the BEM, the GBEM predicts the presence of an intrinsic temperature-independent high-frequency-limiting conductivity whose magnitude is evaluated. The combination of conductive- and dielectric-system response, always experimentally present for a conductive system, is evaluated for the GBEM, and in the frequency range where the GBEM and BEM are indistinguishable it leads to frequency and temperature response remarkably similar to that observed for most disordered materials. Finally, it is suggested that Dyre's macroscopic simulations of the relaxation problem do not seem fully relevant to physical situations of interest and thus should not be taken to confirm

  15. AC conductivity and dielectric relaxation of tris(N,N-dimethylanilinium) hexabromidostannate(IV) bromide: (C8H12N)3SnBr6.Br

    NASA Astrophysics Data System (ADS)

    Chouaib, H.; Kamoun, S.

    2015-10-01

    The X-ray powder analysis, thermogravimetric analysis, differential scanning calorimetry analysis and complex impedance spectroscopic data have been carried out on (C8H12N)3SnBr6.Br compound. The results show that this compound exhibits a phase transition at (T=365±2 K) which has been characterized by differential scanning calorimetry (DSC), AC conductivity and dielectric measurements. The AC conductivity, the modulus analysis, the dielectric constants and the polarizability have been studied using impedance in the temperature range from 334 K to 383 K and in the frequency range between 20 Hz and 2 MHz. The temperature dependence of DC conductivity follows the Arrhenius law. Moreover, the frequency dependence of conductivity follows Jonscher's dynamical law with the relation: σ(ω , T) =σDC + B(T)ω s(T) . Relaxation peaks can be observed in the complex modulus analysis and after a transformation of the complex permittivity ε* to the complex polarizability α*.

  16. Mutation Glu82Lys in lamin A/C gene is associated with cardiomyopathy and conduction defect

    SciTech Connect

    Wang Hu; Wang Jizheng; Zheng Weiyue; Wang Xiaojian; Wang Shuxia; Song Lei; Zou Yubao; Yao Yan; Hui Rutai . E-mail: huirutai@sglab.org

    2006-05-26

    Dilated cardiomyopathy is a form of heart muscle disease characterized by impaired systolic function and ventricular dilation. The mutations in lamin A/C gene have been linked to dilated cardiomyopathy. We screened genetic mutations in a large Chinese family of 50 members including members with dilated cardiomyopathy and found a Glu82Lys substitution mutation in the rod domain of the lamin A/C protein in eight family members, three of them have been diagnosed as dilated cardiomyopathy, one presented with heart dilation. The pathogenic mechanism of lamin A/C gene defect is poorly understood. Glu82Lys mutated lamin A/C and wild type protein was transfected into HEK293 cells. The mutated protein was not properly localized at the inner nuclear membrane and the emerin protein, which interacts with lamin A/C, was also aberrantly distributed. The nuclear membrane structure was disrupted and heterochromatin was aggregated aberrantly in the nucleus of the HEK293 cells stably transfected with mutated lamin A/C gene as determined by transmission electron microscopy.

  17. Motor, emotional, and cognitive empathy in children and adolescents with autism spectrum disorder and conduct disorder.

    PubMed

    Bons, Danielle; van den Broek, Egon; Scheepers, Floor; Herpers, Pierre; Rommelse, Nanda; Buitelaar, Jan K; Buitelaaar, Jan K

    2013-04-01

    It is unclear which aspects of empathy are shared and which are uniquely affected in autism spectrum disorder (ASD) and conduct disorder (CD) as are the neurobiological correlates of these empathy impairments. The aim of this systematic review is to describe the overlap and specificity of motor, emotional, and cognitive aspects of empathy in children and adolescents with ASD or CD. Motor and cognitive empathy impairments are found in both ASD and CD, yet the specificity seems to differ. In ASD facial mimicry and emotion recognition may be impaired for all basic emotions, whereas in CD this is only the case for negative emotions. Emotional empathy and the role of attention to the eyes therein need further investigation. We hypothesize that impaired motor and cognitive empathy in both disorders are a consequence of lack of attention to the eyes. However, we hypothesize major differences in emotional empathy deficits between ASD and CD, probably due to emotional autonomic and amygdala hyper-responsivity in ASD versus hypo-responsivity in CD, both resulting in lack of attention to the eyes.

  18. Ferromagnetic resonance and ac conductivity of a polymer composite of Fe3O4 and Fe3C nanoparticles dispersed in a graphite matrix

    NASA Astrophysics Data System (ADS)

    Guskos, N.; Anagnostakis, E. A.; Likodimos, V.; Bodziony, T.; Typek, J.; Maryniak, M.; Narkiewicz, U.; Kucharewicz, I.; Waplak, S.

    2005-01-01

    Ferromagnetic resonance (FMR) and ac conductivity have been applied to study a polymer composite containing as filler a binary mixture of magnetite (Fe3O4) and cementite (Fe3C) nanoparticles (30-50nm) dispersed in a diamagnetic carbon matrix, which was synthesized by the carburization of nanocrystalline iron. Ac conductivity measurements showed thermally activated behavior involving a range of activation energies and power law frequency dependence at high frequencies similar to conducting polymer composites randomly filled with metal particles. Ferromagnetic resonance measurements revealed a relatively narrow FMR line at high temperatures indicating the presence of ferromagnetic nanoparticles, where thermal fluctuations and interparticle interactions determine the FMR temperature variation. An abrupt change of the FMR spectra was observed at T <81K (ΔT⩽1K) coinciding with a sharp anomaly resolved in the temperature derivative of the ac conductivity. This behavior is attributed to the Verwey transition of Fe3O4 nanoparticles, where the concurrent skin depth variation unveils the FMR of large magnetite conglomerates and thus allows discriminating their contribution from relatively isolated nanoparticles.

  19. Associations between Language Development and Skin Conductance Responses to Faces and Eye Gaze in Children with Autism Spectrum Disorder

    ERIC Educational Resources Information Center

    Stagg, Steven D.; Davis, Robert; Heaton, Pamela

    2013-01-01

    Attention to social stimuli is associated with language development, and arousal is associated with the increased viewing of stimuli. We investigated whether skin conductance responses (SCRs) are associated with language development in autism spectrum disorder (ASD): a population that shows abnormalities in both attention to others and language…

  20. Determining Studies Conducted upon Individuals with Autism Spectrum Disorder Using High-Tech Devices

    ERIC Educational Resources Information Center

    Eliçin, Özge; Kaya, Ali

    2017-01-01

    This study explores 67 experimental research articles written about children with Autism Spectrum Disorder using high-tech devices. The studies in this research were accessed through EBSCO, Academic Search Complete, ERIC, and Uludag University online search engines using keywords such as "autism and technology", "autism and…

  1. AC Electrical Conduction of Cr-Doped SrTiO3 Thin Films with an Oxygen-Deficient Interface Layer

    NASA Astrophysics Data System (ADS)

    Phan, Bach Thang; Eom, Ki Tae; Lee, Jaichan

    2017-01-01

    The ac electrical conduction of Cr-doped SrTiO3 thin films with an oxygen-deficient interface layer was investigated as a function of temperature and frequency. The Cr-doped SrTiO3 (Cr-STO) thin films with an ultra-thin (˜2 nm) oxygen-deficient layer inserted between the top electrode and the Cr-STO layer exhibited two ac conduction mechanisms, i.e., variable-range hopping and small-polaron hopping conduction, accompanied by a relaxation process. Since high oxygen deficiency induces large lattice distortion in the depletion layer, the first relaxation process occurs at low frequencies in the thin oxygen depletion layer Cr-SrTiO3-δ , and the corresponding conduction behavior follows the small-polaron tunneling model. In the high frequency range, an additional relaxation process is involved and is associated with the variable-range hopping between the localized states in the band gap of the thick Cr-SrTiO3 layer.

  2. Dielectric properties and study of AC electrical conduction mechanisms by non-overlapping small polaron tunneling model in Bis(4-acetylanilinium) tetrachlorocuprate(II) compound

    NASA Astrophysics Data System (ADS)

    Abkari, A.; Chaabane, I.; Guidara, K.

    2016-09-01

    In the present work, the synthesis and characterization of the Bis(4-acetylanilinium) tetrachlorocuprate(II) compound are presented. The structure of this compound is analyzed by X-ray diffraction which confirms the formation of single phase and is in good agreement the literature. Indeed, the Thermo gravimetric Analysis (TGA) shows that the decomposition of the compound is observed in the range of 420-520 K. However, the differential thermal analysis (DTA) indicates the presence of a phase transition at T=363 k. Furthermore, the dielectric properties and AC conductivity were studied over a temperature range (338-413 K) and frequency range (200 Hz-5 MHz) using complex impedance spectroscopy. Dielectric measurements confirmed such thermal analyses by exhibiting the presence of an anomaly in the temperature range of 358-373 K. The complex impedance plots are analyzed by an electrical equivalent circuit consisting of resistance, constant phase element (CPE) and capacitance. The activation energy values of two distinct regions are obtained from log σT vs 1000/T plot and are found to be E=1.27 eV (T<363 K) and E=1.09 eV (363 Kac conductivity, σac, has been analyzed by Jonscher's universal power law σ(ω)=σdc+Aωs. The value of s is to be temperature-dependent, which has a tendency to increase with temperature and the non-overlapping small polaron tunneling (NSPT) model is the most applicable conduction mechanism in the title compound. Complex impedance spectra of [C8H10NO]2CuCl4 at different temperatures.

  3. A spectrum domain analysis for the microstrip patch antenna loaded by conducting posts

    NASA Astrophysics Data System (ADS)

    Zhang, W.-X.; Cheng, C.-H.

    Some samples of microstrip patch antennas, loaded or unloaded, with rectangular or equilateral triangle patches are analyzed and computed using the moment method and the spectrum domain method (SDM). A flexible technique for using SDM to analyze a perpendicular current in layered structures is introduced, and an integration technique to improve the convergence is suggested. The results show that loading posts cause a decrease rather than an increase in the resonant frequency.

  4. Conductance of single microRNAs chains related to the autism spectrum disorder

    NASA Astrophysics Data System (ADS)

    Oliveira, J. I. N.; Albuquerque, E. L.; Fulco, U. L.; Mauriz, P. W.; Sarmento, R. G.; Caetano, E. W. S.; Freire, V. N.

    2014-09-01

    The charge transport properties of single-stranded microRNAs (miRNAs) chains associated to autism disorder were investigated. The computations were performed within a tight-binding model, together with a transfer matrix technique, with ionization energies and hopping parameters obtained by quantum chemistry method. Current-voltage (I× V) curves of twelve miRNA chains related to the autism spectrum disorders were calculated and analysed. We have obtained both semiconductor and insulator behavior, and a relationship between the current intensity and the autism-related miRNA bases sequencies, suggesting that a kind of electronic biosensor can be developed to distinguish different profiles of autism disorders.

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

    NASA Astrophysics Data System (ADS)

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

    2016-11-01

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

  6. Crystal structure, NMR study, dielectric relaxation and AC conductivity of a new compound [Cd3(SCN)2Br6(C2H9N2)2]n

    NASA Astrophysics Data System (ADS)

    Saidi, K.; Kamoun, S.; Ayedi, H. Ferid; Arous, M.

    2013-11-01

    The crystal structure, the 13C NMR spectroscopy and the complex impedance have been carried out on [Cd3(SCN)2Br6(C2H9N2)2]n. Crystal structure shows a 2D polymeric network built up of two crystallographically independent cadmium atoms with two different octahedral coordinations. This compound exhibits a phase transition at (T=355±2 K) which has been characterized by differential scanning calorimetry (DSC), X-rays powder diffraction, AC conductivity and dielectric measurements. Examination of 13C CP/MAS line shapes shows indirect spin-spin coupling (14N and 13C) with a dipolar coupling constant of 1339 Hz. The AC conductivity of this compound has been carried out in the temperature range 325-376 K and the frequency range from 10-2 Hz to 10 MHz. The impedance data were well fitted to two equivalent electrical circuits. The results of the modulus study reveal the presence of two distinct relaxation processes. One, at low frequency side, is thermally activated due to the ionic conduction of the crystal and the other, at higher frequency side, gradually disappears when temperature reaches 355 K which is attributed to the localized dipoles in the crystal. Moreover, the temperature dependence of DC-conductivity in both phases follows the Arrhenius law and the frequency dependence of σ(ω,T) follows Jonscher's universal law. The near values of activation energies obtained from the conductivity data and impedance confirm that the transport is through the ion hopping mechanism.

  7. AC conductivity and dielectric properties of 2-(2,3-dihydro-1,5-dimethyl-3-oxo-2-phenyl-1 H-pyrazol-4-ylimino)-2-(4-nitrophenyl)acetonitrile thin films

    NASA Astrophysics Data System (ADS)

    El-Menyawy, E. M.; Zeyada, H. M.; El-Nahass, M. M.

    2010-12-01

    The dark AC conductivity and dielectric properties of thermally evaporated 2-(2,3-dihydro-1,5-dimethyl-3-oxo-2-phenyl-1 H-pyrazol-4-ylimino)-2-(4-nitrophenyl)acetonitrile (DOPNA) thin films in sandwich structure employing symmetrical gold ohmic contacts have been investigated as function of temperature (303-443 K) and frequency (100 Hz-5 MHz). The AC conductivity, σAC( ω), is found to obey Jonscher's universal power law, σAC( ω)= Aω s ( ω is the angular frequency). The AC conductivity of DOPNA thin films has been analyzed with reference to various theoretical models. The correlated barrier hopping is found to be the dominant conduction mechanism for charge carrier transport; the maximum barrier height, hopping length and the density of localized states are estimated. The temperature dependence of the AC conductivity shows Arrhenius type with two thermal activation energies. The activation energies are determined as a function of frequency. The behavior of the real and imaginary parts of the dielectric constant as a function of both temperature and frequency is discussed.

  8. Low-temperature AC conductivity of Bi 2Sr 2CaCu 2O 8+ δ

    NASA Astrophysics Data System (ADS)

    Corson, J.; Orenstein, J.; Eckstein, J. N.; Bozovic, I.

    2000-05-01

    We report measurements of anamolously large dissipative conductivities, σ1, in Bi 2Sr 2CaCu 2O 8+ δ at low temperatures. We have measured the complex conductivity of Bi 2Sr 2CaCu 2O 8+ δ thin films at 100-600 GHz as a function of doping from the underdoped to the overdoped state. At low temperatures there exists a residual σ1 which scales with the T=0 superfluid density as the doping is varied. This residual σ1 is larger than the possible contribution to σ1 from a thermal population of quasiparticles (QP) at the d-wave gap nodes.

  9. Dielectric and AC-conductivity studies of Dy2O3 doped (K0.5Na0.5)NbO3 ceramics

    NASA Astrophysics Data System (ADS)

    Peddigari, Mahesh; Thota, Subhash; Pamu, Dobbidi

    2014-08-01

    (K0.5Na0.5)NbO3 + x wt.% Dy2O3 (x = 0-1.5) ferroelectric ceramics were prepared by conventional solid state reaction method. XRD patterns revealed that orthorhombic symmetry has transformed into psuedocubic symmetry with increasing the substitution of Dy3+ in the Na+ site. Temperature and frequency dependences of relative dielectric permittivity maximum conforms the transformation from normal ferroelectric to relaxor ferroelectric behaviour. Frequency dependence of the relative dielectric permittivity maximum temperature observed for the samples with x ≥ 1.0 and satisfied the Vogel-Fulcher law. The diffuseness exponent γ (1.27-1.95) estimated from the high temperature slopes of the diffused dielectric permittivity data reveals that the degree of relaxor behavior increases with increasing the amount of Dy2O3. The temperature dependence of AC-conductivity σAC (T) analysis in the range 310 K < T < 470 K reveals the existence of variable range hopping of charge carriers with average hopping length RH and hopping energy EH are in the range 8.5-27 Å and 48-153 meV, respectively. Voltage dependent dielectric constant measurements confirm the ferroelectric nature of KNN+ x wt% Dy2O3 ceramics.

  10. Synthesis, crystal structure, NMR study and AC conductivity of [(C3H7)4N]2Cd2ClF5 compound

    NASA Astrophysics Data System (ADS)

    Hajji, Rachid; Oueslati, Abderrazak; Body, Monique; Hlel, Faouzi

    2015-08-01

    The [(C3H7)4N]2Cd2ClF5 compound was crystallized in the triclinic system with space group P1. The crystal structure consists of organic-inorganic layers, stacked along direction. The organic part consists of two cations types. The inorganic layer is made up of Cd2ClF5 dimmers composed of two in-equivalent irregular tetrahedra sharing one edge (Cl-F). The MAS NMR spectra showed two, three and five isotropic resonances relative to 111Cd, 13C and 19F nuclei, respectively. DSC measurement disclosed a phase transition at around 380 K. The impedance spectroscopy and AC electrical conductivity measurements of our compound were taken from 209 Hz to 5 MHz over the temperature range of 350-381 K. Nyquist plots ( Z″ vs Z') show semicircle arcs at different temperatures, and an electrical equivalent circuit has been proposed to explain the impedance results. The circuits consist of the parallel combination of bulk resistance ( R), capacitance ( C) and fractal capacitance (CPE). The conductivity σ p follows the Arrhenius relation. The near value of activation energies obtained from the conductivity data and circuit equivalent confirms that the transport is through hopping mechanism. The analysis of the experimental data shows that the reorientation motion of [N(C3H7)4]+ cations and/or [Cd2ClF5]2- anions is probably responsible for the observed conductivity.

  11. AC impedance analysis of ionic and electronic conductivities in electrode mixture layers for an all-solid-state lithium-ion battery

    NASA Astrophysics Data System (ADS)

    Siroma, Zyun; Sato, Tomohiro; Takeuchi, Tomonari; Nagai, Ryo; Ota, Akira; Ioroi, Tsutomu

    2016-06-01

    The ionic and electronic effective conductivities of an electrode mixture layers for all-solid-state lithium-ion batteries containing Li2Ssbnd P2S5 as a solid electrolyte were investigated by AC impedance measurements and analysis using a transmission-line model (TLM). Samples containing graphite (graphite electrodes) or LiNi0.5Co0.2Mn0.3O2 (NCM electrodes) as the active material were measured under a "substrate | sample | bulk electrolyte | sample | substrate" configuration (ion-electron connection) and a "substrate | sample | substrate" configuration (electron-electron connection). Theoretically, if the electronic resistance is negligibly small, which is the case with our graphite electrodes, measurement with the ion-electron connection should be effective for evaluating ionic conductivity. However, if the electronic resistance is comparable to the ionic resistance, which is the case with our NCM electrodes, the results with the ion-electron connection may contain some inherent inaccuracy. In this report, we theoretically and practically demonstrate the advantage of analyzing the results with the electron-electron connection, which gives both the ionic and electronic conductivities. The similarity of the behavior of ionic conductivity with the graphite and NCM electrodes confirms the reliability of this analysis.

  12. AC conductivity and relaxation mechanism in (Nd1/2Li1/2)(Fe1/2V1/2)O3 ceramics

    NASA Astrophysics Data System (ADS)

    Nath, Susmita; Barik, Subrat Kumar; Choudhary, R. N. P.

    2016-05-01

    In the present study we have synthesized polycrystalline sample of (Nd1/2Li1/2)(Fe1/2V1/2)O3 ceramic by a standard high-temperature solid-state reaction technique. Studies of dielectric and electrical properties of the compound have been carried out in a wide range of temperature (RT - 400 °C) and frequency (1kHz - 1MHz) using complex impedance spectroscopic technique. The imaginary vs. real component of the complex impedance plot (Nyquist plot) of the prepared sample exhibits the existence of grain, grain boundary contributions in the complex electrical parameters and negative temperature coefficient of resistance (NTCR) type behavior like semiconductor. Details study of ac conductivity plot reveals that the material obeys universal Jonscher's power law.

  13. Synthesis and characterization of cancrinite-type zeolite, and its ionic conductivity study by AC impedance analysis

    NASA Astrophysics Data System (ADS)

    Kriaa, A.; Ben Saad, K.; Hamzaoui, A. H.

    2012-12-01

    The synthesis of cancrinite in the system NaOH-SiO2-Al2O3-NaHCO3-H2O was performed, according to methods described in the literature, in an autoclave under hydrothermal conditions at T = 473 K. The electrical properties of cancrinite-type zeolite pellets were investigated by complex impedance spectroscopy in the temperature range 465-800°C. The effect of temperature on impedance parameters was studied using an impedance analyzer in a wide frequency range (1 Hz to 13 MHz). The real and imaginary parts of complex impedance trace semicircles in the complex plane are plotted. The bulk resistance of the material decreases with rise in temperature. This exhibits a typical negative temperature coefficient of resistance (NTCR) behavior of the material. The results of bulk electrical conductivity and its activation energy are presented. The modulus analysis suggests that the electrical transport processes in the material are very likely to be of electronic nature. Relaxation frequencies follow an Arrhenius behavior with activation energy values not comparable to those found for the electrical conductivity.

  14. AC conductivity and dielectric relaxation in Ba(Sm 1/2Nb 1/2)O 3 ceramic

    NASA Astrophysics Data System (ADS)

    Kumar, Pritam; Singh, B. P.; Sinha, T. P.; Singh, N. K.

    2011-01-01

    The complex perovskite oxide a barium samarium niobate (BSN) synthesized by solid-state reaction technique has single phase with cubic structure. The scanning electron micrograph of the sample shows the average grain size of BSN∼1.22 μm. The field dependence of dielectric response and loss tangent were measured in the temperature range from 323 to 463 K and in the frequency range from 50 Hz to 1 MHz. The complex plane impedance plots show the grain boundary contribution for higher value of dielectric constant in the low frequency region. An analysis of the dielectric constant ( ε‧) and loss tangent (tan δ) with frequency was performed assuming a distribution of relaxation times as confirmed by the scaling behaviour of electric modulus spectra. The low frequency dielectric dispersion corresponds to DC conductivity. The logarithmic angular frequency dependence of the loss peak is found to obey the Arrhenius law with an activation energy of 0.71 eV. The frequency dependence of electrical data is also analyzed in the framework of conductivity and electric modulus formalisms. Both these formalisms show qualitative similarities in relaxation times. The scaling behaviour of imaginary part of electric modulus M″ and dielectric loss spectra suggest that the relaxation describes the same mechanism at various temperatures in BSN. All the observations indicate the polydispersive relaxation in BSN.

  15. Experimental and theoretical study of AC electrical conduction mechanisms of Organic-inorganic hybrid compound Bis (4-acetylanilinium) tetrachlorocadmiate (II)

    NASA Astrophysics Data System (ADS)

    Jellibi, A.; Chaabane, I.; Guidara, K.

    2016-06-01

    A new organic-inorganic bis (4-acetylaniline) tetrachlorocadmate [C8H10NO]2[CdCl4] can be obtained by slow evaporation at room temperature and characterized by X-ray powder diffraction. It crystallized in an orthorhombic system (Cmca space group). The material electrical properties were characterized by impedance spectroscopy technique in the frequency range from 209 Hz-5 MHz and temperature 413 to 460 K. Besides, the impedance plots show semicircle arcs at different temperatures and an electrical equivalent circuit has been proposed to interpret the impedance results. The circuits consist of the parallel combination of a resistance (R), capacitance (C) and fractal capacitance (CPE). The variation of the exponent s as a function of temperature suggested that the conduction mechanism in Bis (4-acetylanilinium) tetrachlorocadmiate compound is governed by two processes which can be ascribed to a hopping transport mechanism: correlated barrier hopping (CBH) model below 443 K and the small polaron tunneling (SPT) model above 443 K.

  16. Impedance and AC conductivity study of nano crystalline, fine grained multiferroic bismuth ferrite (BiFeO3), synthesized by microwave sintering

    NASA Astrophysics Data System (ADS)

    Kolte, Jayant; Salame, Paresh H.; Daryapurkar, A. S.; Gopalan, P.

    2015-09-01

    In this paper, major reduction in sintering time,temperautre and significant improvement over final density of sitnered sample is reported for the microwave sintered nanocrystalline BiFeO3 (BFO) ceramic. Also, different sintering time and temperatures have been used to tailor the grain size and the final density of the resulting BFO ceramics synthesized from phase pure BFO nanoparticles ( d ¯ ≈ 10 n m ). Microwave sintering resulted in reducing the sintering time substantially (by 1h), and has resulted in submicron sized grains and high resistivity ˜1.8 GΩ-cm. The AC conductivity is seen to follow the Jonscher's power law behavior, suggesting correlated barrier hopping (CBH) mechanism in the sample. The role of oxygen vacancies at high temperature, due to volatility of bismuth, in dielectric and conductivity behavior is also discussed. Further, the sample displayed dielectric anomaly near magnetic transition temperature (˜180 °C) indicating bearing of magnetic moments on the dielectric properties. Using Impedance Spectroscopy (IS) we have established, the electrical heterogeneity of the ceramic BFO reavealing semiconducting nature of grains and insulating nature of grain boundary. This, formation of network of insulating grain boundaries and semiconducting grains could lead to formation of internal barrier layer capacitance (IBLC) leading to high dielectric constant in microwave sintered BFO.

  17. Electrical conductivity of the quark-gluon plasma and soft photon spectrum in heavy-ion collisions

    DOE PAGES

    Yin, Yi

    2014-10-06

    We extract the electrical conductivity σ0 of the quark gluon plasma (QGP) and study the effects of magnetic field and chiral anomaly on soft photon azimuthal anisotropy, v₂, based on the thermal photon spectrum at 0.4GeV < p⊥< 0.6GeV at the RHIC energy. As a basis for my analysis, we derive the behavior of retarded photon self-energy of a strongly interacting neutral plasma in hydrodynamic regime in the presence of magnetic field and chiral anomaly. By evolving the resulting soft thermal photon production rate over the realistic hydrodynamic background and comparing the results with the data from the PHENIX Collaboration,more » I found that the electrical conductivity at QGP temperature is in the range: 0.4 < σ₀/(e²T) < 1.1, which is comparable with recent studies on lattice. I also compare the contribution from the magnetic field and chiral anomaly to soft thermal photon v₂ with the data. I argue that at the CERN Large Hadron Collider, the chiral magnetic wave would give negative contribution to photon v₂.« less

  18. Electrical conductivity of the quark-gluon plasma and soft photon spectrum in heavy-ion collisions

    SciTech Connect

    Yin, Yi

    2014-10-06

    We extract the electrical conductivity σ0 of the quark gluon plasma (QGP) and study the effects of magnetic field and chiral anomaly on soft photon azimuthal anisotropy, v₂, based on the thermal photon spectrum at 0.4GeV < p⊥< 0.6GeV at the RHIC energy. As a basis for my analysis, we derive the behavior of retarded photon self-energy of a strongly interacting neutral plasma in hydrodynamic regime in the presence of magnetic field and chiral anomaly. By evolving the resulting soft thermal photon production rate over the realistic hydrodynamic background and comparing the results with the data from the PHENIX Collaboration, I found that the electrical conductivity at QGP temperature is in the range: 0.4 < σ₀/(e²T) < 1.1, which is comparable with recent studies on lattice. I also compare the contribution from the magnetic field and chiral anomaly to soft thermal photon v₂ with the data. I argue that at the CERN Large Hadron Collider, the chiral magnetic wave would give negative contribution to photon v₂.

  19. Linking xylem hydraulic conductivity and vulnerability to the leaf economics spectrum--a cross-species study of 39 evergreen and deciduous broadleaved subtropical tree species.

    PubMed

    Kröber, Wenzel; Zhang, Shouren; Ehmig, Merten; Bruelheide, Helge

    2014-01-01

    While the fundamental trade-off in leaf traits related to carbon capture as described by the leaf economics spectrum is well-established among plant species, the relationship of the leaf economics spectrum to stem hydraulics is much less known. Since carbon capture and transpiration are coupled, a close connection between leaf traits and stem hydraulics should be expected. We thus asked whether xylem traits that describe drought tolerance and vulnerability to cavitation are linked to particular leaf traits. We assessed xylem vulnerability, using the pressure sleeve technique, and anatomical xylem characteristics in 39 subtropical tree species grown under common garden conditions in the BEF-China experiment and tested for correlations with traits related to the leaf economics spectrum as well as to stomatal control, including maximum stomatal conductance, vapor pressure deficit at maximum stomatal conductance and vapor pressure deficit at which stomatal conductance is down-regulated. Our results revealed that specific xylem hydraulic conductivity and cavitation resistance were closely linked to traits represented in the leaf economic spectrum, in particular to leaf nitrogen concentration, as well as to log leaf area and leaf carbon to nitrogen ratio but not to any parameter of stomatal conductance. The study highlights the potential use of well-known leaf traits from the leaf economics spectrum to predict plant species' drought resistance.

  20. Reduction of Common-Mode Conducted Noise Emissions in PWM Inverter-fed AC Motor Drive Systems using Optimized Passive EMI Filter

    NASA Astrophysics Data System (ADS)

    Jettanasen, C.; Ngaopitakkul, A.

    2010-10-01

    Conducted electromagnetic interference (EMI) generated by PWM inverter-fed induction motor drive systems, which are currently widely used in many industrial and/or avionic applications, causes severe parasitic current problems, especially at high frequencies (HF). These restrict power electronic drive's evolution. In order to reduce or minimize these EMI problems, several techniques can be applied. In this paper, insertion of an optimized passive EMI filter is proposed. This filter is optimized by taking into account real impedances of each part of a considered AC motor drive system contrarily to commercial EMI filters designed by considering internal impedance of disturbance source and load, equal to 50Ω. Employing the latter EMI filter would make EMI minimization less effective. The proposed EMI filter optimization is mainly dedicated to minimize common mode (CM) currents due to its most dominant effects in this kind of system. The efficiency of the proposed optimization method using two-port network approach is deduced by comparing the minimized CM current spectra to an applied normative level (ex. DO-160D in aeronautics).

  1. Influence of temperature on the electric, dielectric and AC conductivity properties of nano-crystalline zinc substituted cobalt ferrite synthesized by solution combustion technique

    NASA Astrophysics Data System (ADS)

    Rani, Ritu; Kumar, Gagan; Batoo, Khalid M.; Singh, M.

    2014-06-01

    Cobalt-zinc nanoferrites with formulae Co ZnFeO, where x = 0.0, 0.1, 0.2 and 0.3, have been synthesized by solution combustion technique. The variation of DC resistivity with temperature shows the semiconducting behavior of all nanoferrites. The dielectric properties such as dielectric constant (') and dielectric loss tangent (tan are investigated as a function of temperature and frequency. Dielectric constant and loss tangent are found to be increasing with an increase in temperature while with an increase in frequency both, ' and tan , are found to be decreasing. The dielectric properties have been explained on the basis of space charge polarization according to Maxwell-Wagner's two-layer model and the hopping of charge between Fe and Fe. Further, a very high value of dielectric constant and a low value of tan are the prime achievements of the present work. The AC electrical conductivity ( is studied as a function of temperature as well as frequency and is observed to be increasing with the increase in temperature and frequency.

  2. Neural Bases of Theory of Mind in Children with Autism Spectrum Disorders and Children with Conduct Problems and Callous-Unemotional Traits

    ERIC Educational Resources Information Center

    O'Nions, Elizabeth; Sebastian, Catherine L.; McCrory, Eamon; Chantiluke, Kaylita; Happé, Francesca; Viding, Essi

    2014-01-01

    Individuals with autism spectrum disorders (ASD) have difficulty understanding other minds (Theory of Mind; ToM), with atypical processing evident at both behavioural and neural levels. Individuals with conduct problems and high levels of callous-unemotional (CU) traits (CP/HCU) exhibit reduced responsiveness to others' emotions and difficulties…

  3. Differentiating Children with Attention-Deficit/Hyperactivity Disorder, Conduct Disorder, Learning Disabilities and Autistic Spectrum Disorders by Means of Their Motor Behavior Characteristics

    ERIC Educational Resources Information Center

    Efstratopoulou, Maria; Janssen, Rianne; Simons, Johan

    2012-01-01

    The study was designed to investigate the discriminant validity of the Motor Behavior Checklist (MBC) for distinguishing four group of children independently classified with Attention-Deficit/Hyperactivity Disorder, (ADHD; N = 22), Conduct Disorder (CD; N = 17), Learning Disabilities (LD; N = 24) and Autistic Spectrum Disorders (ASD; N = 20).…

  4. The investigation of dielectric properties and ac conductivity of new ceramic diphosphate Ag0.6Na0.4FeP2O7 using impedance spectroscopy method

    NASA Astrophysics Data System (ADS)

    Nasri, S.; Megdiche, M.; Gargouri, M.

    2016-10-01

    In this paper, Ag0.6Na0.4FeP2O7 has been synthesized by solid state reaction method. The ceramic compound was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), vibrational spectroscopy and impedance measurements. In fact, the investigated sample has shown single phase type monoclinic structure with P21/C space group. The frequency-dependent electrical data are analyzed in the frame-work of conductivity and electric modulus formalisms. The real and imaginary parts of complex impedance are well fitted to equivalent circuit model based on the Z-View-software. Besides, the observed frequency dependence of conductivity is found to obey Jonscher's universal law. The temperature dependence of both ac conductivity and the parameter s is reasonably well interpreted by the correlated barrier hopping (CBH). The theoretical fitting between the proposed model and the experimental data showed good agreement. The contribution of single polaron and bipolaron hopping to a.c. conductivity in present compound is also studied. The ionic conductivity is discussed on the basis of the structural characteristics of the sample.

  5. Effect of the light spectrum of various substrates for inkjet printed conductive structures sintered with intense pulsed light

    SciTech Connect

    Weise, Dana Mitra, Kalyan Yoti Ueberfuhr, Peter; Baumann, Reinhard R.

    2015-02-17

    In this work, the novel method of intense pulsed light (IPL) sintering of a nanoparticle silver ink is presented. Various patterns are printed with the Inkjet technology on two flexible foils with different light spectra. One is a clear Polyethylenterephthalat [PET] foil and the second is a light brownish Polyimide [PI] foil. The samples are flashed with different parameters regarding to pulse intensity and pulse length. Microscopic images are indicating the impact of the flashing parameters and the different light spectra of the substrates on the sintered structures. Sheet and line resistance are measured and the conductivity is calculated. A high influence of the property of the substrate with respect to light absorption and thermal conductivity on the functionality of printed conductive structures could be presented. With this new method of IPL sintering, highly conductive inkjet printed silver patterns could be manufactured within milliseconds on flexible polymeric foils without damaging the substrate.

  6. Structural characterization, thermal, ac conductivity and dielectric properties of (C7H12N2)2[SnCl6]Cl2.1.5H2O

    NASA Astrophysics Data System (ADS)

    Hajji, Rachid; Oueslati, Abderrazek; Hajlaoui, Fadhel; Bulou, Alain; Hlel, Faouzi

    2016-05-01

    (C7H12N2)2[SnCl6]Cl2.1.5H2O is crystallized at room temperature in the monoclinic system (space group P21/n). The isolated molecules form organic and inorganic layers parallel to the (a, b) plane and alternate along the c-axis. The inorganic layer is built up by isolated SnCl6 octahedrons. Besides, the organic layer is formed by 2,4-diammonium toluene cations, between which the spaces are filled with free Cl- ions and water molecules. The crystal packing is governed by means of the ionic N-H...Cl and Ow-H...Cl hydrogen bonds, forming a three-dimensional network. The thermal study of this compound is reported, revealing two phase transitions around 360(±3) and 412(±3) K. The electrical and dielectric measurements were reported, confirming the transition temperatures detected in the differential scanning calorimetry (DSC). The frequency dependence of ac conductivity at different temperatures indicates that the correlated barrier hopping (CBH) model is the probable mechanism for the ac conduction behavior.

  7. Cognitive and affective empathy in children with conduct problems: additive and interactive effects of callous-unemotional traits and autism spectrum disorders symptoms.

    PubMed

    Pasalich, Dave S; Dadds, Mark R; Hawes, David J

    2014-11-30

    Callous-unemotional (CU) traits and autism spectrum disorders (ASD) symptoms are characterized by problems in empathy; however, these behavioral features are rarely examined together in children with conduct problems. This study investigated additive and interactive effects of CU traits and ASD symptoms in relation to cognitive and affective empathy in a non-ASD clinic-referred sample. Participants were 134 children aged 3 to 9 years (M=5.60; 79% boys) with oppositional defiant/conduct disorder, and their parents. Clinicians, teachers, and parents reported on dimensions of child behavior, and parental reports of family dysfunction and direct observations of parental warmth/responsiveness assessed quality of family relationships. Results from multiple regression analysis showed that, over and above the effects of child conduct problem severity and quality of family relationships, both ASD symptoms and CU traits were uniquely associated with deficits in cognitive empathy. Moreover, CU traits demonstrated an independent association with affective empathy, and this relationship was moderated by ASD symptoms. That is, there was a stronger negative association between CU traits and affective empathy at higher versus lower levels of ASD symptoms. These findings suggest including both CU traits and ASD-related social impairments in models delineating the atypical development of empathy in children with conduct problems.

  8. Dielectric Relaxation Behavior and AC Electrical Conductivity Study of 2-(1,2-Dihydro-7-Methyl-2-Oxoquinoline-5-yl) Malononitrile (DMOQMN)

    NASA Astrophysics Data System (ADS)

    El-Nahass, M. M.; El-Zaidia, E. F. M.; Darwish, A. A. A.; Salem, G. F.

    2017-02-01

    Dielectric relaxation and alternative current conductivity of a new organic compound 2-(1,2-dihydro-7-methyl-2-oxoquinoline-5-yl) malononitrile (DMOQMN) have been investigated. X-ray diffraction (XRD) at room temperature reveals that DMOQMN samples have a polycrystalline structure of the triclinic system. The analysis of the dielectric constant and dielectric loss index suggested the dominant polarization is performed and the Maxwell-Wagner-Sillar type polarization is dominating at low frequency and high temperature. These results have been confirmed by the XRD and dielectric modulus. The estimated relaxation time and the activation energy are 9 × 10-13 s and 0.43 eV, respectively. Our results indicated that the conduction mechanism of DMOQMN is controlled by the correlation barrier hopping (CBH) model.

  9. Studies on structural, thermal and AC conductivity scaling of PEO-LiPF6 polymer electrolyte with added ionic liquid [BMIMPF6

    NASA Astrophysics Data System (ADS)

    Chaurasia, S. K.; Saroj, A. L.; Shalu, Singh, V. K.; Tripathi, A. K.; Gupta, A. K.; Verma, Y. L.; Singh, R. K.

    2015-07-01

    Preparation and characterization of polymer electrolyte films of PEO+10wt.% LiPF6 + xwt.% BMIMPF6 (1-butyl-3-methylimidazolium hexafluorophosphate) containing dopant salt lithium hexafluorophosphate (LiPF6) and ionic liquid (BMIMPF6) having common anion PF6 - are reported. The ionic conductivity of the polymer electrolyte films has been found to increase with increasing concentration of BMIMPF6 in PEO+10 wt.% LiPF6 due to the plasticization effect of ionic liquid. DSC and XRD results show that the crystallinity of polymer electrolyte decreases with BMIMPF6 concentration which, in turn, is responsible for the increase in ionic conductivity. FTIR spectroscopic study shows the complexation of salt and/or ionic liquid cations with the polymer backbone. Ion dynamics behavior of PEO+LiPF6 as well as PEO+LiPF6 + BMIMPF6 polymer electrolytes was studied by frequency dependent conductivity, σ(f) measurements. The values σ(f) at various temperatures have been analyzed in terms of Jonscher power law (JPL) and scaled with respect to frequency which shows universal power law characteristics at all temperatures.

  10. Differentiating children with attention-deficit/hyperactivity disorder, conduct disorder, learning disabilities and autistic spectrum disorders by means of their motor behavior characteristics.

    PubMed

    Efstratopoulou, Maria; Janssen, Rianne; Simons, Johan

    2012-01-01

    The study was designed to investigate the discriminant validity of the Motor Behavior Checklist (MBC) for distinguishing four group of children independently classified with Attention-Deficit/Hyperactivity Disorder, (ADHD; N=22), Conduct Disorder (CD; N=17), Learning Disabilities (LD; N=24) and Autistic Spectrum Disorders (ASD; N=20). Physical education teachers used the MBC for children to rate their pupils based on their motor related behaviors. A multivariate analysis revealed significant differences among the groups on different problem scales. The results indicated that the MBC for children may be effective in discriminating children with similar disruptive behaviors (e.g., ADHD, CD) and autistic disorders, based on their motor behavior characteristics, but not children with Learning Disabilities (LD), when used by physical education teachers in school settings.

  11. Oppositional defiant and conduct disorder behaviors in boys with autism spectrum disorder with and without attention-deficit hyperactivity disorder versus several comparison samples.

    PubMed

    Guttmann-Steinmetz, Sarit; Gadow, Kenneth D; Devincent, Carla J

    2009-07-01

    We compared disruptive behaviors in boys with either autism spectrum disorder (ASD) plus ADHD (n = 74), chronic multiple tic disorder plus ADHD (n = 47), ADHD Only (n = 59), or ASD Only (n = 107). Children were evaluated with parent and teacher versions of the Child Symptom Inventory-4 including parent- (n = 168) and teacher-rated (n = 173) community controls. Parents rated children in the three ADHD groups comparably for each symptom of oppositional defiant disorder (ODD) and conduct disorder. Teacher ratings indicated that the ASD + ADHD group evidenced a unique pattern of ODD symptom severity, differentiating them from the other ADHD groups, and from the ASD Only group. The clinical features of ASD appear to influence co-morbid, DSM-IV-defined ODD, with implications for nosology.

  12. AC photovoltaic module magnetic fields

    SciTech Connect

    Jennings, C.; Chang, G.J.; Reyes, A.B.; Whitaker, C.M.

    1997-12-31

    Implementation of alternating current (AC) photovoltaic (PV) modules, particularly for distributed applications such as PV rooftops and facades, may be slowed by public concern about electric and magnetic fields (EMF). This paper documents magnetic field measurements on an AC PV module, complementing EMF research on direct-current PV modules conducted by PG and E in 1993. Although not comprehensive, the PV EMF data indicate that 60 Hz magnetic fields (the EMF type of greatest public concern) from PV modules are comparable to, or significantly less than, those from household appliances. Given the present EMF research knowledge, AC PV module EMF may not merit considerable concern.

  13. AC Electrokinetics of Physiological Fluids for Biomedical Applications.

    PubMed

    Lu, Yi; Liu, Tingting; Lamanda, Ariana C; Sin, Mandy L Y; Gau, Vincent; Liao, Joseph C; Wong, Pak Kin

    2015-12-01

    Alternating current (AC) electrokinetics is a collection of processes for manipulating bulk fluid mass and embedded objects with AC electric fields. The ability of AC electrokinetics to implement the major microfluidic operations, such as pumping, mixing, concentration, and separation, makes it possible to develop integrated systems for clinical diagnostics in nontraditional health care settings. The high conductivity of physiological fluids presents new challenges and opportunities for AC electrokinetics-based diagnostic systems. In this review, AC electrokinetic phenomena in conductive physiological fluids are described followed by a review of the basic microfluidic operations and the recent biomedical applications of AC electrokinetics. The future prospects of AC electrokinetics for clinical diagnostics are presented.

  14. AC Electrokinetics of Physiological Fluids for Biomedical Applications

    PubMed Central

    Lu, Yi; Liu, Tingting; Lamanda, Ariana C.; Sin, Mandy L Y; Gau, Vincent; Liao, Joseph C.; Wong, Pak Kin

    2016-01-01

    AC electrokinetics is a collection of processes for manipulating bulk fluid mass and embedded objects with AC electric fields. The ability of AC electrokinetics to implement the major microfluidic operations, such as pumping, mixing, concentration and separation, makes it possible to develop integrated systems for clinical diagnostics in non-traditional healthcare settings. The high conductivity of physiological fluids presents new challenges and opportunities for AC electrokinetics based diagnostic systems. In this review, AC electrokinetic phenomena in conductive physiological fluids are described followed by a review of the basic microfluidic operations and the recent biomedical applications of AC electrokinetics. The future prospects of AC electrokinetics for clinical diagnostics are presented. PMID:25487557

  15. Microstructure, AC impedance and DC electrical conductivity characteristics of NiFe2-xGdxO4 (x = 0, 0.05 and 0.075)

    NASA Astrophysics Data System (ADS)

    Kamala Bharathi, K.; Markandeyulu, G.; Ramana, C. V.

    2012-03-01

    The structure and electrical characteristics of Gd doped Ni ferrite materials, namely NiFe1.95Gd0.05O4 and NiFe1.925Gd0.075O4, are reported to demonstrate their improved electrical properties compared to that of pure NiFe2O4. NiFe1.95Gd0.05O4 and NiFe1.925Gd0.075O4 compounds crystallize in the cubic inverse spinel phase with a very small amount of GdFeO3 additional phase while pure NiFe2O4 crystallize in inverse spinel phase without any impurity phase. The back scattered electron imaging analysis indicate the primary and secondary formation in NiFe1.95Gd0.05O4 and NiFe1.925Gd0.075O4 compounds. Atomic force microscopy measurements indicate that the bulk grains are ˜2-5 micron size while the grain boundaries are thin compared to bulk grains. Impedance spectroscopic analysis at different temperature indicates the different relaxation mechanisms and their variation with temperature, bulk grain and grain-boundary contributions to the electrical conductivity (Rg) and capacitance (Cg) of these materials. The conductivity in pure NiFeO4 is found to be predominantly due to intrinsic bulk contribution (Rg=213 kΩ and Cg=4.5 x 10-8 F). In the case of NiFe1.95Gd0.05O4 and NiFe1.925Gd0.075O4 compounds, grain and grain-boundary contributions to the conductivity are clearly observed. The DC conductivity values (at 300 K) of NiFe2O4, NiFe1.95Gd0.05O4 and NiFe1.925Gd0.075O4 compounds are found to be 1.06 x 10-7 Ω-1 cm-1, 5.73 x 10-8 Ω-1 cm-1 and 1.28 x 10-8 Ω-1 cm-1 respectively.

  16. Interrelationship between Number of Mobile Protons, Diffusion Coefficient, and AC Conductivity in Superprotonic Conductors, CsHSO4 and Rb3H(SeO4)2

    NASA Astrophysics Data System (ADS)

    Kamazawa, Kazuya; Harada, Masashi; Araki, Toru; Matsuo, Yasumitsu; Tyagi, Madhusudan; Sugiyama, Jun

    2014-07-01

    Using quasielastic neutron scattering (QENS), we investigated the proton dynamics for two superprotonic conductors, CsHSO4 and Rb3H(SeO4)2. To evaluate the self-diffusion coefficients and the number of mobile protons on both superprotonic and normal phases, we focused on proton dynamics not only in the phase above Tc, but also in the phase below Tc. In Rb3H(SeO4)2, the self-diffusion of protons was observed even below the Tc phase. In contrast to popular belief, no large changes in the self-diffusion coefficients were observed across Tc. Nevertheless, the increase in the number of mobile protons across Tc was about 14.5 times, which was estimated from the integrated intensity of QENS spectra, and this change could not account for the increased magnitude of proton conductivity, which is about 500 times. As a large translational self-diffusion coefficient has not been reported in previous works by QENS experiments, there are still unknown factors that contribute to the Nernst-Einstein relation that need to be discovered.

  17. Analyses of temperature-dependent interface states, series resistances, and AC electrical conductivities of Al/p—Si and Al/Bi4Ti3O12/p—Si structures by using the admittance spectroscopy method

    NASA Astrophysics Data System (ADS)

    Mert, Yıldırım; Perihan, Durmuş; Şemsettin, Altındal

    2013-10-01

    In this study, Al/p—Si and Al/Bi4Ti3O12/p—Si structures are fabricated and their interface states (Nss), the values of series resistance (Rs), and AC electrical conductivityac) are obtained each as a function of temperature using admittance spectroscopy method which includes capacitance—voltage (C—V) and conductance—voltage (G—V) measurements. In addition, the effect of interfacial Bi4Ti3O12 (BTO) layer on the performance of the structure is investigated. The voltage-dependent profiles of Nss and Rs are obtained from the high-low frequency capacitance method and the Nicollian method, respectively. Experimental results show that Nss and Rs, as strong functions of temperature and applied bias voltage, each exhibit a peak, whose position shifts towards the reverse bias region, in the depletion region. Such a peak behavior is attributed to the particular distribution of Nss and the reordering and restructuring of Nss under the effect of temperature. The values of activation energy (Ea), obtained from the slope of the Arrhenius plot, of both structures are obtained to be bias voltage-independent, and the Ea of the metal-ferroelectric-semiconductor (MFS) structure is found to be half that of the metal—semiconductor (MS) structure. Furthermore, other main electrical parameters, such as carrier concentration of acceptor atoms (NA), built-in potential (Vbi), Fermi energy (EF), image force barrier lowering (Δ Φb), and barrier height (Φb), are extracted using reverse bias C-2—V characteristics as a function of temperature.

  18. Neural bases of Theory of Mind in children with autism spectrum disorders and children with conduct problems and callous-unemotional traits

    PubMed Central

    O'Nions, Elizabeth; Sebastian, Catherine L; McCrory, Eamon; Chantiluke, Kaylita; Happé, Francesca; Viding, Essi

    2014-01-01

    Individuals with autism spectrum disorders (ASD) have difficulty understanding other minds (Theory of Mind; ToM), with atypical processing evident at both behavioural and neural levels. Individuals with conduct problems and high levels of callous-unemotional (CU) traits (CP/HCU) exhibit reduced responsiveness to others' emotions and difficulties interacting with others, but nonetheless perform normally in experimental tests of ToM. The present study aimed to examine the neural underpinnings of ToM in children (aged 10–16) with ASD (N = 16), CP/HCU (N = 16) and typically developing (TD) controls (N = 16) using a non-verbal cartoon vignette task. Whilst individuals with ASD were predicted to show reduced fMRI responses across regions involved in ToM processing, CP/HCU individuals were predicted to show no differences compared with TD controls. The analyses indicated that neural responses did not differ between TD and CP/HCU groups during ToM. TD and CP/HCU children exhibited significantly greater medial prefrontal cortex responses during ToM than did the ASD group. Within the ASD group, responses in medial prefrontal cortex and right temporoparietal junction (TPJ) correlated with symptom severity as measured by the Autism Diagnostic Observation Schedule (ADOS). Findings suggest that although both ASD and CP/HCU are characterized by social difficulties, only children with ASD display atypical neural processing associated with ToM. PMID:24636205

  19. Deuterium isotope effects on the ionization constant of acetic acid in H2O and D2O by AC conductance from 368 to 548 K at 20 MPa.

    PubMed

    Erickson, K M; Arcis, H; Raffa, D; Zimmerman, G H; Tremaine, P R

    2011-03-31

    Values of the ionization constant of acetic acid in H(2)O and D(2)O (K(HAc) and K(DAc)) and the deuterium isotope effect, ΔpK = pK(DAc) - pK(HAc), have been determined from T = 368 K to T = 548 K at p = 20 MPa, using a flow-through ac conductance cell built at the University of Delaware. Measurements were made on dilute (ionic strength ∼ 10(-4) mol·kg(-1)) solutions of acetic acid, sodium acetate, hydrochloric acid, and sodium chloride in H(2)O and D(2)O, injected in sequence at each temperature and pressure, so that systematic errors in the measured conductance of each solution would cancel. Experimental values for the molar conductivity, Λ, of the strong electrolytes were used to calculate the molar conductivity at infinite dilution, Λ°, using the Fuoss-Hsia-Fernández-Prini (FHFP) equation. These were used to calculate the molar conductivity at infinite dilution for acetic acid which was in turn used to calculate the degree of dissociation and finally the ionization constants of acetic acid. This same procedure was done for the pertinent deuterated solutes in D(2)O. Measured values of log K(HAc), log K(DAc), and ΔpK were obtained to a precision of ±0.008. The present results are in agreement with the only other accurate study at high temperatures and pressures (Mesmer, R. E.; Herting, D. L. J. Solution Chem.1978, 7, 901-913). The deuterium isotope effects, ΔpK, become independent of temperature above ∼420 K, at a value approximately 0.1 unit lower than that at 298 K. These values are ΔpK = 0.43 ± 0.01 and ΔpK = 0.51 ± 0.01, respectively. The temperature dependence of the Walden product ratio, (λ°η)(D(2)O)/(λ°η)(H(2)O), indicates a change in the relative hydration behavior of ions, whereby the effective Stokes radii of the sodium, chloride, and acetate ions in D(2)O relative to H(2)O reverse above ∼423 K. The results also suggest that the greater efficiency of the well-established proton-hopping transport mechanisms for OH(-) and H(3)O

  20. Evaluation of the Fourier Frequency Spectrum Peaks of Milk Electrical Conductivity Signals as Indexes to Monitor the Dairy Goats’ Health Status by On-Line Sensors

    PubMed Central

    Zaninelli, Mauro; Agazzi, Alessandro; Costa, Annamaria; Tangorra, Francesco Maria; Rossi, Luciana; Savoini, Giovanni

    2015-01-01

    The aim of this study is a further characterization of the electrical conductivity (EC) signal of goat milk, acquired on-line by EC sensors, to identify new indexes representative of the EC variations that can be observed during milking, when considering not healthy (NH) glands. Two foremilk gland samples from 42 Saanen goats, were collected for three consecutive weeks and for three different lactation stages (LS: 0–60 Days In Milking (DIM); 61–120 DIM; 121–180 DIM), for a total amount of 1512 samples. Bacteriological analyses and somatic cells counts (SCC) were used to define the health status of the glands. With negative bacteriological analyses and SCC < 1,000,000 cells/mL, glands were classified as healthy. When bacteriological analyses were positive or showed a SCC > 1,000,000 cells/mL, glands were classified as NH. For each milk EC signal, acquired on-line and for each gland considered, the Fourier frequency spectrum of the signal was calculated and three representative frequency peaks were identified. To evaluate data acquired a MIXED procedure was used considering the HS, LS and LS × HS as explanatory variables in the statistical model.Results showed that the studied frequency peaks had a significant relationship with the gland’s health status. Results also explained how the milk EC signals’ pattern change in case of NH glands. In fact, it is characterized by slower fluctuations (due to the lower frequencies of the peaks) and by an irregular trend (due to the higher amplitudes of all the main frequency peaks). Therefore, these frequency peaks could be used as new indexes to improve the performances of algorithms based on multivariate models which evaluate the health status of dairy goats through the use of gland milk EC sensors. PMID:26307993

  1. Evaluation of the Fourier Frequency Spectrum Peaks of Milk Electrical Conductivity Signals as Indexes to Monitor the Dairy Goats' Health Status by On-Line Sensors.

    PubMed

    Zaninelli, Mauro; Agazzi, Alessandro; Costa, Annamaria; Tangorra, Francesco Maria; Rossi, Luciana; Savoini, Giovanni

    2015-08-21

    The aim of this study is a further characterization of the electrical conductivity (EC) signal of goat milk, acquired on-line by EC sensors, to identify new indexes representative of the EC variations that can be observed during milking, when considering not healthy (NH) glands. Two foremilk gland samples from 42 Saanen goats, were collected for three consecutive weeks and for three different lactation stages (LS: 0-60 Days In Milking (DIM); 61-120 DIM; 121-180 DIM), for a total amount of 1512 samples. Bacteriological analyses and somatic cells counts (SCC) were used to define the health status of the glands. With negative bacteriological analyses and SCC < 1,000,000 cells/mL, glands were classified as healthy. When bacteriological analyses were positive or showed a SCC > 1,000,000 cells/mL, glands were classified as NH. For each milk EC signal, acquired on-line and for each gland considered, the Fourier frequency spectrum of the signal was calculated and three representative frequency peaks were identified. To evaluate data acquired a MIXED procedure was used considering the HS, LS and LS × HS as explanatory variables in the statistical model.Results showed that the studied frequency peaks had a significant relationship with the gland's health status. Results also explained how the milk EC signals' pattern change in case of NH glands. In fact, it is characterized by slower fluctuations (due to the lower frequencies of the peaks) and by an irregular trend (due to the higher amplitudes of all the main frequency peaks). Therefore, these frequency peaks could be used as new indexes to improve the performances of algorithms based on multivariate models which evaluate the health status of dairy goats through the use of gland milk EC sensors.

  2. Training Adults with an Autism Spectrum Disorder to Conduct Discrete-Trial Training for Young Children with Autism: A Pilot Study

    ERIC Educational Resources Information Center

    Lerman, Dorothea C.; Hawkins, Lynn; Hoffman, Rachel; Caccavale, Mia

    2013-01-01

    We evaluated a behavioral skills training program for adults with autism spectrum disorder and mild or no intellectual disabilities who were interested in learning the skills used by behavior therapists to work with young children with autism and other developmental disabilities. Four adults, aged 21 to 30 years, participated. We trained each…

  3. Oppositional Defiant and Conduct Disorder Behaviors in Boys with Autism Spectrum Disorder with and without Attention-Deficit Hyperactivity Disorder versus Several Comparison Samples

    ERIC Educational Resources Information Center

    Guttmann-Steinmetz, Sarit; Gadow, Kenneth D.; DeVincent, Carla J.

    2009-01-01

    We compared disruptive behaviors in boys with either autism spectrum disorder (ASD) plus ADHD (n = 74), chronic multiple tic disorder plus ADHD (n = 47), ADHD Only (n = 59), or ASD Only (n = 107). Children were evaluated with parent and teacher versions of the Child Symptom Inventory-4 including parent- (n = 168) and teacher-rated (n = 173)…

  4. Comprehensive analysis of human cells motion under an irrotational AC electric field in an electro-microfluidic chip.

    PubMed

    Vaillier, Clarisse; Honegger, Thibault; Kermarrec, Frédérique; Gidrol, Xavier; Peyrade, David

    2014-01-01

    AC electrokinetics is a versatile tool for contact-less manipulation or characterization of cells and has been widely used for separation based on genotype translation to electrical phenotypes. Cells responses to an AC electric field result in a complex combination of electrokinetic phenomena, mainly dielectrophoresis and electrohydrodynamic forces. Human cells behaviors to AC electrokinetics remain unclear over a large frequency spectrum as illustrated by the self-rotation effect observed recently. We here report and analyze human cells behaviors in different conditions of medium conductivity, electric field frequency and magnitude. We also observe the self-rotation of human cells, in the absence of a rotational electric field. Based on an analytical competitive model of electrokinetic forces, we propose an explanation of the cell self-rotation. These experimental results, coupled with our model, lead to the exploitation of the cell behaviors to measure the intrinsic dielectric properties of JURKAT, HEK and PC3 human cell lines.

  5. Comprehensive Analysis of Human Cells Motion under an Irrotational AC Electric Field in an Electro-Microfluidic Chip

    PubMed Central

    Kermarrec, Frédérique; Gidrol, Xavier; Peyrade, David

    2014-01-01

    AC electrokinetics is a versatile tool for contact-less manipulation or characterization of cells and has been widely used for separation based on genotype translation to electrical phenotypes. Cells responses to an AC electric field result in a complex combination of electrokinetic phenomena, mainly dielectrophoresis and electrohydrodynamic forces. Human cells behaviors to AC electrokinetics remain unclear over a large frequency spectrum as illustrated by the self-rotation effect observed recently. We here report and analyze human cells behaviors in different conditions of medium conductivity, electric field frequency and magnitude. We also observe the self-rotation of human cells, in the absence of a rotational electric field. Based on an analytical competitive model of electrokinetic forces, we propose an explanation of the cell self-rotation. These experimental results, coupled with our model, lead to the exploitation of the cell behaviors to measure the intrinsic dielectric properties of JURKAT, HEK and PC3 human cell lines. PMID:24736275

  6. Phonon spectrum in a CdSe nanowire

    NASA Astrophysics Data System (ADS)

    Barrett, Chris; Wang, Lin-Wang

    2011-03-01

    It is important to calculate the phonon spectrum of realistic nanowires, e.g. to understand its thermo conductivity or to calculate the electron-phonon interaction. In this talk, we will present results of phonon spectrum calculation using valence force field (VFF) method. An important issue is to construct the VFF to describe the surface atomic displacement. We have developed a general VFF formalism to fit our VFF result with the density functional theory (DFT) calculated surface atom displacement energies. In particular, the (10-10) CdSe surface is modelled with Cd-Se dimerization. We will discuss the quality of such VFF model. The phonon spectrum of the nanowire will be presented, and its implication on the phonon transport and electron-phonon coupling will also be discussed. This work is supported by U.S. Department of Energy BES, office of science, under Contract No. DE-AC02-05CH11231.

  7. ACS: ALMA Common Software

    NASA Astrophysics Data System (ADS)

    Chiozzi, Gianluca; Šekoranja, Matej

    2013-02-01

    ALMA Common Software (ACS) provides a software infrastructure common to all ALMA partners and consists of a documented collection of common patterns and components which implement those patterns. The heart of ACS is based on a distributed Component-Container model, with ACS Components implemented as CORBA objects in any of the supported programming languages. ACS provides common CORBA-based services such as logging, error and alarm management, configuration database and lifecycle management. Although designed for ALMA, ACS can and is being used in other control systems and distributed software projects, since it implements proven design patterns using state of the art, reliable technology. It also allows, through the use of well-known standard constructs and components, that other team members whom are not authors of ACS easily understand the architecture of software modules, making maintenance affordable even on a very large project.

  8. Microtubule alignment and manipulation using AC electrokinetics.

    PubMed

    Uppalapati, Maruti; Huang, Ying-Ming; Jackson, Thomas N; Hancock, William O

    2008-09-01

    The kinesin-microtubule system plays an important role in intracellular transport and is a model system for integrating biomotor-driven transport into microengineered devices. AC electrokinetics provides a novel tool for manipulating and organizing microtubules in solution, enabling new experimental geometries for investigating and controlling the interactions of microtubules and microtubule motors in vitro. By fabricating microelectrodes on glass substrates and generating AC electric fields across solutions of microtubules in low-ionic-strength buffers, bundles of microtubules are collected and aligned and the electrical properties of microtubules in solution are measured. The AC electric fields result in electro-osmotic flow, electrothermal flow, and dielectrophoresis of microtubules, which can be controlled by varying the solution conductivity, AC frequency, and electrode geometry. By mapping the solution conductivity and AC frequency over which positive dielectrophoresis occurs, the apparent conductivity of taxol-stabilized bovine-brain microtubules in PIPES buffer is measured to be 250 mS m(-1). By maximizing dielectrophoretic forces and minimizing electro-osmotic and electrothermal flow, microtubules are assembled into opposed asters. These experiments demonstrate that AC electrokinetics provides a powerful new tool for kinesin-driven transport applications and for investigating the role of microtubule motors in development and maintenance of the mitotic spindle.

  9. Training adults with an autism spectrum disorder to conduct discrete-trial training for young children with autism: a pilot study.

    PubMed

    Lerman, Dorothea C; Hawkins, Lynn; Hoffman, Rachel; Caccavale, Mia

    2013-01-01

    We evaluated a behavioral skills training program for adults with autism spectrum disorder and mild or no intellectual disabilities who were interested in learning the skills used by behavior therapists to work with young children with autism and other developmental disabilities. Four adults, aged 21 to 30 years, participated. We trained each individually using verbal and written instructions, modeling, and role play with feedback to teach 2 basic skills to an adult who played the role of a young child with autism. We evaluated generalization of the discrete-trial training skills by having the participant (a) teach the adult confederate 2 additional targets that we had not included in training and (b) teach a new skill to a young child with autism. Results indicated that 3 of the 4 participants rapidly acquired discrete-trial training skills and that these skills generalized to new targets with the confederate adults and to teaching an actual child with autism.

  10. The AC-120: The advanced commercial transport

    NASA Technical Reports Server (NTRS)

    Duran, David; Griffin, Ernest; Mendoza, Saul; Nguyen, Son; Pickett, Tim; Noernberg, Clemm

    1993-01-01

    The main objective of this design was to fulfill a need for a new airplane to replace the aging 100 to 150 passenger, 1500 nautical mile range aircraft such as the Douglas DC9 and Boeing 737-100 airplanes. After researching the future aircraft market, conducting extensive trade studies, and analysis on different configurations, the AC-120 Advanced Commercial Transport final design was achieved. The AC-120's main design features include the incorporation of a three lifting surface configuration which is powered by two turboprop engines. The AC-120 is an economically sensitive aircraft which meets the new FM Stage Three noise requirements, and has lower NO(x) emissions than current turbofan powered airplanes. The AC-120 also improves on its contemporaries in passenger comfort, manufacturing, and operating cost.

  11. Microfabricated AC impedance sensor

    DOEpatents

    Krulevitch, Peter; Ackler, Harold D.; Becker, Frederick; Boser, Bernhard E.; Eldredge, Adam B.; Fuller, Christopher K.; Gascoyne, Peter R. C.; Hamilton, Julie K.; Swierkowski, Stefan P.; Wang, Xiao-Bo

    2002-01-01

    A microfabricated instrument for detecting and identifying cells and other particles based on alternating current (AC) impedance measurements. The microfabricated AC impedance sensor includes two critical elements: 1) a microfluidic chip, preferably of glass substrates, having at least one microchannel therein and with electrodes patterned on both substrates, and 2) electrical circuits that connect to the electrodes on the microfluidic chip and detect signals associated with particles traveling down the microchannels. These circuits enable multiple AC impedance measurements of individual particles at high throughput rates with sufficient resolution to identify different particle and cell types as appropriate for environmental detection and clinical diagnostic applications.

  12. AC magnetohydrodynamic microfluidic switch

    SciTech Connect

    Lemoff, A V; Lee, A P

    2000-03-02

    A microfluidic switch has been demonstrated using an AC Magnetohydrodynamic (MHD) pumping mechanism in which the Lorentz force is used to pump an electrolytic solution. By integrating two AC MHD pumps into different arms of a Y-shaped fluidic circuit, flow can be switched between the two arms. This type of switch can be used to produce complex fluidic routing, which may have multiple applications in {micro}TAS.

  13. Zellweger Spectrum

    MedlinePlus

    ... Resources Conference News Contact Us Donate The Zellweger Spectrum Zellweger Syndrome, Neonatal Adrenoleukodystrophy (NALD), and Infantile Refsum’s ... of severity of disease. What causes the Zellweger spectrum of diseases? As we mentioned, disorders of the ...

  14. ac electroosmosis in rectangular microchannels.

    PubMed

    Campisi, Michele; Accoto, Dino; Dario, Paolo

    2005-11-22

    Motivated by the growing interest in ac electroosmosis as a reliable no moving parts strategy to control fluid motion in microfluidic devices for biomedical applications, such as lab-on-a-chip, we study transient and steady-state electrokinetic phenomena (electroosmosis and streaming currents) in infinitely extended rectangular charged microchannels. With the aid of Fourier series and Laplace transforms we provide a general formal solution of the problem, which is used to study the time-dependent response to sudden ac applied voltage differences in case of finite electric double layer. The Debye-Huckel approximation has been adopted to allow for an algebraic solution of the Poisson-Boltzmann problem in Fourier space. We obtain the expressions of flow velocity profiles, flow rates, streaming currents, as well as expressions of the complex hydraulic and electrokinetic conductances. We analyze in detail the dependence of the electrokinetic conductance on the extension of linear dimensions relative to the Debye length, with an eye on finite electric double layer effects.

  15. ac electroosmosis in rectangular microchannels

    NASA Astrophysics Data System (ADS)

    Campisi, Michele; Accoto, Dino; Dario, Paolo

    2005-11-01

    Motivated by the growing interest in ac electroosmosis as a reliable no moving parts strategy to control fluid motion in microfluidic devices for biomedical applications, such as lab-on-a-chip, we study transient and steady-state electrokinetic phenomena (electroosmosis and streaming currents) in infinitely extended rectangular charged microchannels. With the aid of Fourier series and Laplace transforms we provide a general formal solution of the problem, which is used to study the time-dependent response to sudden ac applied voltage differences in case of finite electric double layer. The Debye-Hückel approximation has been adopted to allow for an algebraic solution of the Poisson-Boltzmann problem in Fourier space. We obtain the expressions of flow velocity profiles, flow rates, streaming currents, as well as expressions of the complex hydraulic and electrokinetic conductances. We analyze in detail the dependence of the electrokinetic conductance on the extension of linear dimensions relative to the Debye length, with an eye on finite electric double layer effects.

  16. Tevatron AC dipole system

    SciTech Connect

    Miyamoto, R.; Kopp, S.E.; Jansson, A.; Syphers, M.J.; /Fermilab

    2007-06-01

    The AC dipole is an oscillating dipole magnet which can induce large amplitude oscillations without the emittance growth and decoherence. These properties make it a good tool to measure optics of a hadron synchrotron. The vertical AC dipole for the Tevatron is powered by an inexpensive high power audio amplifier since its operating frequency is approximately 20 kHz. The magnet is incorporated into a parallel resonant system to maximize the current. The use of a vertical pinger magnet which has been installed in the Tevatron made the cost relatively inexpensive. Recently, the initial system was upgraded with a more powerful amplifier and oscillation amplitudes up to 2-3{sigma} were achieved with the 980 GeV proton beam. This paper discusses details of the Tevatron AC dipole system and also shows its test results.

  17. ACS CCDs daily monitor

    NASA Astrophysics Data System (ADS)

    Sirianni, Marco

    2006-07-01

    This program consists of a set of basic tests to monitor, the read noise, thedevelopment of hot pixels and test for any source of noise in ACS CCDdetectors. The files, biases and dark will be used to create referencefiles for science calibration. This programme will be for the entire lifetime of ACS.For cycle 15 the program will cover 18 months 12.1.06->05.31.08and it has been divied into three different proposal each covering six months.The three poroposal are 11041-11042-11043.

  18. ac bidirectional motor controller

    NASA Technical Reports Server (NTRS)

    Schreiner, K.

    1988-01-01

    Test data are presented and the design of a high-efficiency motor/generator controller at NASA-Lewis for use with the Space Station power system testbed is described. The bidirectional motor driver is a 20 kHz to variable frequency three-phase ac converter that operates from the high-frequency ac bus being designed for the Space Station. A zero-voltage-switching pulse-density-modulation technique is used in the converter to shape the low-frequency output waveform.

  19. Numerical simulation of ac plasma arc thermodynamics

    NASA Astrophysics Data System (ADS)

    Wu, Han-Ming; Carey, G. F.; Oakes, M. E.

    1994-05-01

    A mathematical model and approximate analysis for the energy distribution of an ac plasma arc with a moving boundary is developed. A simplified electrical conductivity function is assumed so that the dynamic behavior of the arc may be determined, independent of the gas type. The model leads to a reduced set of non-linear partial differential equations which governs the quasi-steady ac arc. This system is solved numerically and it is found that convection plays an important role, not only in the temperature distribution, but also in arc disruptions. Moreover, disruptions are found to be influenced by convection only for a limited frequency range. The results of the present studies are applicable to the frequnecy range of 10-10(exp 2) Hz which includes most industry ac arc frequencies.

  20. Numerical Simulation of AC Plasma Arc Thermodynamics

    NASA Astrophysics Data System (ADS)

    Wu, Han-Ming; Carey, G. F.; Oakes, M. E.

    1994-05-01

    A mathematical model and approximate analysis for the energy distribution of an ac plasma arc with a moving boundary is developed. A simplified electrical conductivity function is assumed so that the dynamic behavior of the arc may be determined, independent of the gas type. The model leads to a reduced set of non-linear partial differential equations which governs the quasi-steady ac arc. This system is solved numerically and it is found that convection plays an important role, not only in the temperature distribution, but also in arc disruptions. Moreover, disruptions are found to be influenced by convection only for a limited frequency range. The results of the present studies are applicable to the frequency range of 10-102 Hz which includes most industry ac arc frequencies.

  1. Ac magnetorestriction hysteresis and magnetization direction in grain oriented silicon steels

    SciTech Connect

    Mogi, Hisashi; Matsuo, Yukio; Kumano, Tomoji

    1999-09-01

    A hysteresis curve of ac magnetostriction was measured, magnetizing a grain oriented silicon steel in the direction deviated from rolling direction of a sample. The ac magnetostriction ({lambda} ac) curves were analyzed as harmonics in the interest of noise spectrum of such as a power transformer. The domain structure model in this magnetostriction process was proposed. The hysteresis was large in the magnetization direction inclined at 30 and 90{degree} from the rolling direction.

  2. AC/DC converter

    NASA Astrophysics Data System (ADS)

    Jain, Praveen K.

    1992-08-01

    In a system such as a 20 kHz space station primary electrical power distribution system, power conversion from AC to DC is required. Some of the basic requirements for this conversion are high efficiency, light weight and small volume, regulated output voltage, close to unity input power factor, distortionless input current, soft-starting, low electromagnetic interference, and high reliability. An AC-to-DC converter is disclosed which satisfies the main design objectives of such converters for use in space. The converter of the invention comprises an input transformer, a resonant network, a current controller, a diode rectifier, and an output filter. The input transformer is for connection to a single phase, high frequency, sinusoidal waveform AC voltage source and provides a matching voltage isolating from the AC source. The resonant network converts this voltage to a sinusoidal, high frequency bidirectional current output, which is received by the current controller to provide the desired output current. The diode rectifier is connected in parallel with the current controller to convert the bidirectional current into a unidirectional current output. The output filter is connected to the rectifier to provide an essentially ripple-free, substantially constant voltage DC output.

  3. AC/RF Superconductivity

    SciTech Connect

    Ciovati, Gianluigi

    2015-02-01

    This contribution provides a brief introduction to AC/RF superconductivity, with an emphasis on application to accelerators. The topics covered include the surface impedance of normal conductors and superconductors, the residual resistance, the field dependence of the surface resistance, and the superheating field.

  4. The A to Z of A/C plasmids.

    PubMed

    Harmer, Christopher J; Hall, Ruth M

    2015-07-01

    Plasmids belonging to incompatibility groups A and C (now A/C) were among the earliest to be associated with antibiotic resistance in Gram-negative bacteria. A/C plasmids are large, conjugative plasmids with a broad host range. The prevalence of A/C plasmids in collections of clinical isolates has revealed their importance in the dissemination of extended-spectrum β-lactamases and carbapenemases. They also mobilize SGI1-type resistance islands. Revived interest in the family has yielded many complete A/C plasmid sequences, revealing that RA1, designated A/C1, is different from the remainder, designated A/C2. There are two distinct A/C2 lineages. Backbones of 128-130 kb include over 120 genes or ORFs encoding proteins of at least 100 amino acids, but very few have been characterized. Genes potentially required for replication, stability and transfer have been identified, but only the replication system of RA1 and the regulation of transfer have been studied. There is enormous variety in the antibiotic resistance genes carried by A/C2 plasmids but they are usually clustered in larger regions at various locations in the backbone. The ARI-A and ARI-B resistance islands are always at a specific location but have variable content. ARI-A is only found in type 1 A/C2 plasmids, which disseminate blaCMY-2 and blaNDM-1 genes, whereas ARI-B, carrying the sul2 gene, is found in both type 1 and type 2. This review summarizes current knowledge of A/C plasmids, and highlights areas of research to be considered in the future.

  5. Evaluation of modern IGBT-modules for hard-switched AC/DC/AC converters

    SciTech Connect

    Blaabjerg, F.; Pedersen, J.K.; Jaeger, U.

    1995-12-31

    The development of IGBT devices is still producing faster devices with lower losses. The applications become more advanced like a complete hard-switched AC/DC/AC converter with almost clean input current and regenerating capabilities. This paper will first focus on a detailed characterization and comparison of eight different IGBT-modules representing state-of-the-art for both PT and NPT technologies. The voltage level of the devices is 1,200V and 1,600V/1,700V. The characterization is done on an advanced measurement system which is briefly described. The characterization is based on static and dynamic tests for both IGBT and the diodes in the IGBT-modules at a junction temperature at 125 C. The comparison is first done directly based on conduction losses and switching losses, and later the measurements are used in a loss model for a complete AC/DC/AC converter application. In the AC/DC/AC converter the power losses are modelled, and different operating conditions are compared like different voltage levels in the DC-link. It is concluded dependent on operation conditions different devices will be preferable, but the high voltage devices have the highest losses even at a high operating voltage.

  6. Spectrum Recombination.

    ERIC Educational Resources Information Center

    Greenslade, Thomas B., Jr.

    1984-01-01

    Describes several methods of executing lecture demonstrations involving the recombination of the spectrum. Groups the techniques into two general classes: bringing selected portions of the spectrum together using lenses or mirrors and blurring the colors by rapid movement or foreshortening. (JM)

  7. Characterization and Conductivity Behavior of Magnetic Activated Carbon (MAC) from FeCl2.4H2O-Containing Carbon

    NASA Astrophysics Data System (ADS)

    Aripin, Department Of Physics, Faculty Of Mathematics; Natural Science, Haluoleo University, Kampus Bumi Tridharma Anduonohu Kendari 93232 Indonesia

    2007-05-01

    Activated carbons (AC) and magnetic-containing activated carbons (MAC) have been synthesized using coconut shells as carbon sources and FeCl2.4H2O as magnetic precursor. The samples were characterized by nitrogen sorption, XRD, and FTIR. The BET surface area and total pore volume of MAC increase as the temperature increased. AC has XRD peaks, which evidences an amorphous carbon framework and MAC shows that this material consists of an organized carbon with the nanocrystalline magnetite embedded in its structure. The FTIR spectrum of MAC shows that carboxyl groups decreased as the temperature increased. Absorption bands of MAC shows the stretching and torsional vibration modes of the magnetite Fe-O bond in tetrahedral and octahedral sites, respectively. The electrical conductivity studies showed that conductivity of MAC is more than the AC due to structural properties of carbons exists on a framework containing metal structures.

  8. Structural characterization and AC conductivity of bis tetrapropylammonium hexachlorado-dicadmate, [N(C{sub 3}H{sub 7}){sub 4}]{sub 2}Cd{sub 2}Cl{sub 6}

    SciTech Connect

    Hannachi, N.; Guidara, K.; Bulou, A.; Hlel, F.

    2010-11-15

    Synthesis, crystal structure, vibrational study, {sup 13}C, {sup 111}Cd CP-MAS-NMR analysis and electrical properties of the compound [N(C{sub 3}H{sub 7}){sub 4}]{sub 2}Cd{sub 2}Cl{sub 6}, are reported. The latter crystallizes in the triclinic system (space group P1-bar, Z = 2) with the following unit cell dimensions: a = 9.530(1) A, b = 11.744(1) A, c = 17.433(1) A, {alpha} = 79.31(1){sup o}, {beta} = 84.00(1){sup o} and {gamma} = 80.32(1){sup o}. Besides, its structure was solved using 6445 independent reflections down to R = 0.037. The atomic arrangement can be described by alternating organic and inorganic layers parallel to the (11-bar 0) plan, made up of tetrapropylammonium groups and Cd{sub 2}Cl{sub 6} dimers, respectively. In crystal structure, the inorganic layer, built up by Cd{sub 2}Cl{sub 6} dimers, is connected to the organic ones through van der Waals interaction in order to build cation-anion-cation cohesion. Impedance spectroscopy study, reported in the sample, reveals that the conduction in the material is due to a hopping process. The temperature and frequency dependence of dielectric constants of the single crystal sample has been investigated to determine some related parameters to the dielectric relaxation.

  9. Optimal design of AC filter circuits in HVDC converter stations

    SciTech Connect

    Saied, M.M.; Khader, S.A.

    1995-12-31

    This paper investigates the reactive power as well as the harmonic conditions on both the valve and the AC-network sides of a HVDC converter station. The effect of the AC filter circuits is accurately modeled. The program is then augmented by adding an optimization routine. It can identify the optimal filter configuration, yielding the minimum current distortion factor at the AC network terminals for a prespecified fundamental reactive power to be provided by the filter. Several parameter studies were also conducted to illustrate the effect of accidental or intentional deletion of one of the filter branches.

  10. AC resistance measuring instrument

    DOEpatents

    Hof, P.J.

    1983-10-04

    An auto-ranging AC resistance measuring instrument for remote measurement of the resistance of an electrical device or circuit connected to the instrument includes a signal generator which generates an AC excitation signal for application to a load, including the device and the transmission line, a monitoring circuit which provides a digitally encoded signal representing the voltage across the load, and a microprocessor which operates under program control to provide an auto-ranging function by which range resistance is connected in circuit with the load to limit the load voltage to an acceptable range for the instrument, and an auto-compensating function by which compensating capacitance is connected in shunt with the range resistance to compensate for the effects of line capacitance. After the auto-ranging and auto-compensation functions are complete, the microprocessor calculates the resistance of the load from the selected range resistance, the excitation signal, and the load voltage signal, and displays of the measured resistance on a digital display of the instrument. 8 figs.

  11. AC Resistance measuring instrument

    DOEpatents

    Hof, Peter J.

    1983-01-01

    An auto-ranging AC resistance measuring instrument for remote measurement of the resistance of an electrical device or circuit connected to the instrument includes a signal generator which generates an AC excitation signal for application to a load, including the device and the transmission line, a monitoring circuit which provides a digitally encoded signal representing the voltage across the load, and a microprocessor which operates under program control to provide an auto-ranging function by which range resistance is connected in circuit with the load to limit the load voltage to an acceptable range for the instrument, and an auto-compensating function by which compensating capacitance is connected in shunt with the range resistance to compensate for the effects of line capacitance. After the auto-ranging and auto-compensation functions are complete, the microprocessor calculates the resistance of the load from the selected range resistance, the excitation signal, and the load voltage signal, and displays of the measured resistance on a digital display of the instrument.

  12. AC Optimal Power Flow

    SciTech Connect

    2016-10-04

    In this work, we have implemented and developed the simulation software to implement the mathematical model of an AC Optimal Power Flow (OPF) problem. The objective function is to minimize the total cost of generation subject to constraints of node power balance (both real and reactive) and line power flow limits (MW, MVAr, and MVA). We have currently implemented the polar coordinate version of the problem. In the present work, we have used the optimization solver, Knitro (proprietary and not included in this software) to solve the problem and we have kept option for both the native numerical derivative evaluation (working satisfactorily now) as well as for analytical formulas corresponding to the derivatives being provided to Knitro (currently, in the debugging stage). Since the AC OPF is a highly non-convex optimization problem, we have also kept the option for a multistart solution. All of these can be decided by the user during run-time in an interactive manner. The software has been developed in C++ programming language, running with GCC compiler on a Linux machine. We have tested for satisfactory results against Matpower for the IEEE 14 bus system.

  13. Identification of /sup 233/Ac

    SciTech Connect

    Chu, Y.Y.; Zhou, M.L.

    1983-09-01

    We report in this paper identification of the new isotope /sup 233/Ac. Uranium targets were irradiated with 28 GeV protons; after rapid retrieval of the target and separation of actinium from thorium, /sup 233/Ac was allowed to decay into the known /sup 233/Th daughter. Exhaustive chemical purification was employed to permit the identification of /sup 233/Th via its characteristic ..gamma.. radiations. The half-life derived for /sup 233/Ac from several experiments is 2.3 +- 0.3 min. The production cross section for /sup 233/Ac is 100 ..mu..b.

  14. AC-electric field dependent electroformation of giant lipid vesicles.

    PubMed

    Politano, Timothy J; Froude, Victoria E; Jing, Benxin; Zhu, Yingxi

    2010-08-01

    Giant vesicles of larger than 5 microm, which have been of intense interest for their potential as drug delivery vehicles and as a model system for cell membranes, can be rapidly formed from a spin-coated lipid thin film under an electric field. In this work, we explore the AC-field dependent electroformation of giant lipid vesicles in aqueous media over a wide range of AC-frequency from 1 Hz to 1 MHz and peak-to-peak field strength from 0.212 V/mm to 40 V/mm between two parallel conducting electrode surfaces. By using fluorescence microscopy, we perform in-situ microscopic observations of the structural evolution of giant vesicles formed from spin-coated lipid films under varied uniform AC-electric fields. The real-time observation of bilayer bulging from the lipid film, vesicle growth and fusing further examine the critical role of AC-induced electroosmotic flow of surrounding fluids for giant vesicle formation. A rich AC-frequency and field strength phase diagram is obtained experimentally to predict the AC-electroformation of giant unilamellar vesicles (GUVs) of l-alpha-phosphatidylcholine, where a weak dependence of vesicle size on AC-frequency is observed at low AC-field voltages, showing decreased vesicle size with a narrowed size distribution with increased AC-frequency. Formation of vesicles was shown to be constrained by an upper field strength of 10 V/mm and an upper AC-frequency of 10 kHz. Within these parameters, giant lipid vesicles were formed predominantly unilamellar and prevalent across the entire electrode surfaces.

  15. Theory of hopping conductivity in pig insulin

    NASA Astrophysics Data System (ADS)

    Ye, Yuan-Jie; Ladik, János

    1993-08-01

    The ac conductivity for a native protein, pig insulin, was calculated in the ab initio scheme using Clementi's minimal basis set. The hopping centers and ``main residue'' of an orbital are defined. It is assumed that the hopping events of charge carriers happen among these centers of main residues. The analysis of primary hopping events shows that there might be a relationship between the distribution of the hopping centers and the biochemical activity of insulin, and that the disulfur bridges of insulin have particular relevance for the ac conduction. The formulas for calculation of the ac conductivity of proteins are given. The results show that the curve of the frequency versus ac conductivity of pig insulin lies in the range of some typical inorganic amorphous conductors and confirm that proteins if doped are amorphous conductors. Finally, the possibility of direct comparison of the theoretical results with experiments is discussed.

  16. Digital ac monitor

    DOEpatents

    Hart, George W.; Kern, Jr., Edward C.

    1987-06-09

    An apparatus and method is provided for monitoring a plurality of analog ac circuits by sampling the voltage and current waveform in each circuit at predetermined intervals, converting the analog current and voltage samples to digital format, storing the digitized current and voltage samples and using the stored digitized current and voltage samples to calculate a variety of electrical parameters; some of which are derived from the stored samples. The non-derived quantities are repeatedly calculated and stored over many separate cycles then averaged. The derived quantities are then calculated at the end of an averaging period. This produces a more accurate reading, especially when averaging over a period in which the power varies over a wide dynamic range. Frequency is measured by timing three cycles of the voltage waveform using the upward zero crossover point as a starting point for a digital timer.

  17. Digital ac monitor

    DOEpatents

    Hart, G.W.; Kern, E.C. Jr.

    1987-06-09

    An apparatus and method is provided for monitoring a plurality of analog ac circuits by sampling the voltage and current waveform in each circuit at predetermined intervals, converting the analog current and voltage samples to digital format, storing the digitized current and voltage samples and using the stored digitized current and voltage samples to calculate a variety of electrical parameters; some of which are derived from the stored samples. The non-derived quantities are repeatedly calculated and stored over many separate cycles then averaged. The derived quantities are then calculated at the end of an averaging period. This produces a more accurate reading, especially when averaging over a period in which the power varies over a wide dynamic range. Frequency is measured by timing three cycles of the voltage waveform using the upward zero crossover point as a starting point for a digital timer. 24 figs.

  18. Cooling Floor AC Systems

    NASA Astrophysics Data System (ADS)

    Jun, Lu; Hao, Ding; Hong, Zhang; Ce, Gao Dian

    The present HVAC equipments for the residential buildings in the Hot-summer-and-Cold-winter climate region are still at a high energy consuming level. So that the high efficiency HVAC system is an urgently need for achieving the preset government energy saving goal. With its advantage of highly sanitary, highly comfortable and uniform of temperature field, the hot-water resource floor radiation heating system has been widely accepted. This paper has put forward a new way in air-conditioning, which combines the fresh-air supply unit and such floor radiation system for the dehumidification and cooling in summer or heating in winter. By analyze its advantages and limitations, we found that this so called Cooling/ Heating Floor AC System can improve the IAQ of residential building while keep high efficiency quality. We also recommend a methodology for the HVAC system designing, which will ensure the reduction of energy cost of users.

  19. Automated ac galvanomagnetic measurement system

    NASA Technical Reports Server (NTRS)

    Szofran, F. R.; Espy, P. N.

    1985-01-01

    An automated, ac galvanomagnetic measurement system is described. Hall or van der Pauw measurements in the temperature range 10-300 K can be made at a preselected magnetic field without operator attendance. Procedures to validate sample installation and correct operation of other system functions, such as magnetic field and thermometry, are included. Advantages of ac measurements are discussed.

  20. Dielectric relaxation and alternating current conductivity of lanthanum, gadolinium, and erbium-polyvinyl alcohol doped films

    NASA Astrophysics Data System (ADS)

    Hanafy, Taha A.

    2012-08-01

    Fourier transform infrared (FTIR) spectrum dielectric constant, ɛ', loss tangent, tan(δ), electric modulus, M*, and ac conductivity, σac, of pure polyvinyl alcohol (PVA) as well as La-, Gd-, and Er-PVA doped samples have been carried out. The dielectric properties have been studied in the temperature and frequency ranges; 300-450 K and 1 kHz-4 MHz, respectively. FTIR measurements reveal that La3+, Gd3+, and Er3+ ions form complex configuration within PVA structure. Two relaxation processes, namely, ρ and α were observed in pure PVA sample. The first process is due to the interfacial or Maxwell-Wagner-Sillers polarization. The second one is related to the micro-Brownian motion of the main chains. For doped PVA samples, α-relaxation process splits into αa and αc. This splitting is due to the segmental motion in the amorphous (αa) and crystalline (αc) phases of PVA matrix. Electric modulus analysis was discussed to understand the mechanism of the electrical transport process. The behavior of ac conductivity for all PVA samples indicates that the conduction mechanism is correlated barrier hopping.

  1. Dielectric and AC conductivity studies of Nd substituted 0.8BaTiO3-0.2(Bi0.5(1-x)Nd0.5xK0.5)TiO3 lead free ceramics

    NASA Astrophysics Data System (ADS)

    Ramesh, M. N. V.; Ramesh, K. V.

    2016-05-01

    0.8BaTiO3 - 0.2(Bi0.5(1-x)Nd0.5xK0.5)TiO3 (0.01 ≤ x ≤ 0.06) lead free ceramic materials have been prepared by solid state reaction method and followed by high energy ball milling process. X-ray diffraction studies confirm the tetragonal structure of the materials at room temperature. Lattice parameters and density are decreasing with increase of Nd substitution. Microstructure studies were done by using Scanning electron microscope and it found that grain size is decreasing with increase of Nd substitution. Temperature and frequency dependent dielectric studies reveal relaxor behaviour of the materials. Dielectric constant, dielectric loss and Curie temperature are decreasing with Nd substitution. Maximum Curie temperature of 195°C was observed at 1MHz for x=0.01 Nd substituted sample. Degree of diffuseness was calculated from the modified Curie-Weiss law and it is increasing with Nd substitution. AC conductivity is increasing with increase of Nd substitution and observed maximum activation energy of 0.52 eV for x=0.02 Nd substituted sample.

  2. Perceptions of breath alcohol concentration (BrAC) levels among a sample of bar patrons with BrAC values of 0.08% or higher.

    PubMed

    Martin, Ryan J; Chaney, Beth H; Cremeens-Matthews, Jennifer; Vail-Smith, Karen

    2016-09-01

    Breath alcohol concentration (BrAC) is a commonly used measure of alcohol intoxication. Because of the potential negative consequences of excessive alcohol consumption, it is important to examine how accurately intoxicated individuals can estimate their BrAC values, especially individuals over the legal BrAC driving threshold (i.e., 0.08%). To better understand perceptions of BrAC values among intoxicated individuals, this field study examined actual BrAC values and BrAC range estimates (0.08% and above, 0.02-0.07%, less than 0.02%) among a sample of bar patrons (N = 454) with BrAC levels at 0.08% or higher. Bivariate and multivariate analyses were conducted to examine the relationship between actual BrAC values and perceived BrAC levels. We also examined whether the following demographic and drinking variables were associated with underestimating BrAC in this sample: gender, age, race, college student status, plans to get home, and hazardous drinking. Results indicated that the majority (60.4%) of participants underestimated their BrAC (i.e., less than 0.08%) and lower BrAC values correlated with underestimating BrAC ranges (p < .001, 95% CI[0.2, 0.6]). Further, females (p = .001, 95% CI[1.3, 3.3]) and participants under 21 (p = .039, 95% CI = 1.0, 2.6) were significantly more likely to estimate their BrAC to be less than 0.08%, which is concerning given that young (less than 21) intoxicated females are a group at high risk for sexual assault on college campuses. (PsycINFO Database Record

  3. Phylogenetic ecology of the freshwater Actinobacteria acI lineage.

    PubMed

    Newton, Ryan J; Jones, Stuart E; Helmus, Matthew R; McMahon, Katherine D

    2007-11-01

    The acI lineage of freshwater Actinobacteria is a cosmopolitan and often numerically dominant member of lake bacterial communities. We conducted a survey of acI 16S rRNA genes and 16S-23S rRNA internal transcribed spacer regions from 18 Wisconsin lakes and used standard nonphylogenetic and phylogenetic statistical approaches to investigate the factors that determine acI community composition at the local scale (within lakes) and at the regional scale (across lakes). Phylogenetic reconstruction of 434 acI 16S rRNA genes revealed a well-defined and highly resolved phylogeny. Eleven previously unrecognized monophyletic clades, each with > or =97.9% within-clade 16S rRNA gene sequence identity, were identified. Clade community similarity positively correlated with lake environmental similarity but not with geographic distance, implying that the lakes represent a single biotic region containing environmental filters for communities that have similar compositions. Phylogenetically disparate clades within the acI lineage were most abundant at the regional scale, and local communities were comprised of more closely related clades. Lake pH was a strong predictor of the community composition, but only when lakes with a pH below 6 were included in the data set. In the remaining lakes (pH above 6) biogeographic patterns in the landscape were instead a predictor of the observed acI community structure. The nonrandom distribution of the newly defined acI clades suggests potential ecophysiological differences between the clades, with acI clades AI, BII, and BIII preferring acidic lakes and acI clades AII, AVI, and BI preferring more alkaline lakes.

  4. Structural, Optical and AC Electrical Properties of Ce3+-Doped TiO2-SiO2 Matrices

    NASA Astrophysics Data System (ADS)

    Vidyadharan, Viji; Vasudevan, Prathibha; Karthika, S.; Joseph, Cyriac; Unnikrishnan, N. V.; Biju, P. R.

    2015-08-01

    We report the structural, photoluminescence and alternating current (AC) electrical properties of Ce3+-doped titanosilicate matrices prepared by nonhydrolytic sol-gel method, with different annealing temperatures. The structural characterization of the prepared samples was done by x-ray diffraction, energy dispersive spectrum and Fourier transform infrared spectroscopy measurements. The thermal stability of the prepared matrices was studied by the differential scanning calorimetric analysis. The photoluminescence spectrum shows two luminescence bands centered at 360 nm and 464 nm corresponding to the transitions 2D3/2 to 2F7/2 and 2F5/2, respectively. The dielectric responses of the samples were investigated for the frequency range 1 kHz-3 MHz at room temperature. The variation of AC conductivity, real part of dielectric constant ɛ' and imaginary part of dielectric constant ɛ″ with frequency were also studied. The Cole-Cole parameters were calculated and the semicircles observed in the plots indicate a single relaxation process which can be modelled by an equivalent parallel resistor-capacitor circuit.

  5. Layoff Handling Still Lags ACS Standards.

    ERIC Educational Resources Information Center

    Chemical and Engineering News, 1981

    1981-01-01

    Reviews termination procedures of professional chemists and the compliance of these terminations to the American Chemical Society's (ACS's) Professional Employment Guidelines. Provides the ACS guidelines. (DS)

  6. Phase modulation mode of scanning ion conductance microscopy

    SciTech Connect

    Li, Peng; Zhang, Changlin; Liu, Lianqing E-mail: gli@engr.pitt.edu; Wang, Yuechao; Yang, Yang; Li, Guangyong E-mail: gli@engr.pitt.edu

    2014-08-04

    This Letter reports a phase modulation (PM) mode of scanning ion conductance microscopy. In this mode, an AC current is directly generated by an AC voltage between the electrodes. The portion of the AC current in phase with the AC voltage, which is the current through the resistance path, is modulated by the tip-sample distance. It can be used as the input of feedback control to drive the scanner in Z direction. The PM mode, taking the advantages of both DC mode and traditional AC mode, is less prone to electronic noise and DC drift but maintains high scanning speed. The effectiveness of the PM mode has been proven by experiments.

  7. Indicators: Conductivity

    EPA Pesticide Factsheets

    Conductivity is a measure of the ability of water to pass an electrical current. Because dissolved salts and other inorganic chemicals conduct electrical current, conductivity increases as salinity increases.

  8. Fission Spectrum

    DOE R&D Accomplishments Database

    Bloch, F.; Staub, H.

    1943-08-18

    Measurements of the spectrum of the fission neutrons of 25 are described, in which the energy of the neutrons is determined from the ionization produced by individual hydrogen recoils. The slow neutrons producing fission are obtained by slowing down the fast neutrons from the Be-D reaction of the Stanford cyclotron. In order to distinguish between fission neutrons and the remaining fast cyclotron neutrons both the cyclotron current and the pusle amplifier are modulated. A hollow neutron container, in which slow neutrons have a lifetime of about 2 milliseconds, avoids the use of large distances. This method results in much higher intensities than the usual modulation arrangement. The results show a continuous distribution of neutrons with a rather wide maximum at about 0.8 MV falling off to half of its maximum value at 2.0 MV. The total number of netrons is determined by comparison with the number of fission fragments. The result seems to indicate that only about 30% of the neutrons have energies below .8 MV. Various tests are described which were performed in order to rule out modification of the spectrum by inelastic scattering. Decl. May 4, 1951

  9. AC electrophoretic deposition of organic-inorganic composite coatings.

    PubMed

    Yoshioka, T; Chávez-Valdez, A; Roether, J A; Schubert, D W; Boccaccini, A R

    2013-02-15

    Alternating current electrophoretic deposition (AC-EPD) of polyacrylic acid (PAA)-titanium oxide (TiO(2)) nanoparticle composites on stainless steel electrodes was investigated in basic aqueous solution. AC square wave with duty cycle of 80% was applied at a frequency of 1 kHz. FTIR-ATR spectra showed that both AC and direct current (DC) EPD successfully deposited PAA-TiO(2) composites. The deposition rate using AC-EPD was lower than that obtained in direct current DC-EPD. However, the microstructure and surface morphology of the deposited composite coatings were different depending on the type of electric field applied. AC-EPD applied for not more than 5 min led to smooth films without bubble formation, while DC-EPD for 1 min or more showed deposits with microstructural defects possibly as result of water electrolysis. AC-EPD was thus for the first time demonstrated to be a suitable technique to deposit organic-inorganic composite coatings from aqueous suspensions, showing that applying a square wave and frequency of 1 kHz leads to uniform PAA-TiO(2) composite coatings on conductive materials.

  10. Lagrangian Frequency Spectrum as a Diagnostic for Magnetohydrodynamic Turbulence Dynamics

    SciTech Connect

    Busse, Angela; Mueller, Wolf-Christian; Gogoberidze, Grigol

    2010-12-03

    For the phenomenological description of magnetohydrodynamic turbulence competing models exist, e.g., Boldyrev [Phys. Rev. Lett. 96, 115002 (2006)] and Gogoberidze [Phys. Plasmas 14, 022304 (2007)], which predict the same Eulerian inertial-range scaling of the turbulent energy spectrum although they employ fundamentally different basic interaction mechanisms. A relation is found that links the Lagrangian frequency spectrum with the autocorrelation time scale of the turbulent fluctuations {tau}{sub ac} and the associated cascade time scale {tau}{sub cas}. Thus, the Lagrangian energy spectrum can serve to identify weak ({tau}{sub ac}<<{tau}{sub cas}) and strong ({tau}{sub ac{approx}{tau}cas}) interaction mechanisms providing insight into the turbulent energy cascade. The new approach is illustrated by results from direct numerical simulations of two- and three-dimensional incompressible MHD turbulence.

  11. A type III ACC synthase, ACS7, is involved in root gravitropism in Arabidopsis thaliana.

    PubMed

    Huang, Shih-Jhe; Chang, Chia-Lun; Wang, Po-Hsun; Tsai, Min-Chieh; Hsu, Pang-Hung; Chang, Ing-Feng

    2013-11-01

    Ethylene is an important plant hormone that regulates developmental processes in plants. The ethylene biosynthesis pathway is a highly regulated process at both the transcriptional and post-translational level. The transcriptional regulation of these ethylene biosynthesis genes is well known. However, post-translational modifications of the key ethylene biosynthesis enzyme 1-aminocyclopropane-1-carboxylate (ACC) synthase (ACS) are little understood. In vitro kinase assays were conducted on the type III ACS, AtACS7, fusion protein and peptides to determine whether the AtACS7 protein can be phosphorylated by calcium-dependent protein kinase (CDPK). AtACS7 was phosphorylated at Ser216, Thr296, and Ser299 by AtCDPK16 in vitro. To investigate further the function of the ACS7 gene in Arabidopsis, an acs7-1 loss-of-function mutant was isolated. The acs7-1 mutant exhibited less sensitivity to the inhibition of root gravitropism by treatment with the calcium chelator ethylene glycol tetraacetic acid (EGTA). Seedlings were treated with gradient concentrations of ACC. The results showed that a certain concentration of ethylene enhanced the gravity response. Moreover, the acs7-1 mutant was less sensitive to inhibition of the gravity response by treatment with the auxin polar transport inhibitor 1-naphthylphthalamic acid, but exogenous ACC application recovered root gravitropism. Altogether, the results indicate that AtACS7 is involved in root gravitropism in a calcium-dependent manner in Arabidopsis.

  12. NONLINEAR DIAGNOSTICS USING AC DIPOLES.

    SciTech Connect

    PEGGS,S.

    1999-03-29

    There are three goals in the accurate nonlinear diagnosis of a storage ring. First, the beam must be moved to amplitudes many times the natural beam size. Second, strong and long lasting signals must be generated. Third, the measurement technique should be non-destructive. Conventionally, a single turn kick moves the beam to large amplitudes, and turn-by-turn data are recorded from multiple beam position monitors (BPMs) [1-6]. Unfortunately, tune spread across the beam causes the center of charge beam signal to ''decohere'' on a time scale often less than 100 turns. Filamentation also permanently destroys the beam emittance (in a hadron ring). Thus, the ''strong single turn kick'' technique successfully achieves only one out of the three goals. AC dipole techniques can achieve all three. Adiabatically excited AC dipoles slowly move the beam out to large amplitudes. The coherent signals then recorded last arbitrarily long. The beam maintains its original emittance if the AC dipoles are also turned off adiabatically, ready for further use. The AGS already uses an RF dipole to accelerate polarized proton beams through depolarizing resonances with minimal polarization loss [7]. Similar AC dipoles will be installed in the horizontal and vertical planes of both rings in RHIC [8]. The RHIC AC dipoles will also be used as spin flippers, and to measure linear optical functions [9].

  13. Electrical Conductivity.

    ERIC Educational Resources Information Center

    Allen, Philip B.

    1979-01-01

    Examines Drude's classical (1900) theory of electrical conduction, details the objections to and successes of the 1900 theory, and investigates the Quantum (1928) theory of conduction, reviewing its successes and limitations. (BT)

  14. Study of AC/RF properties of SRF ingot niobium

    SciTech Connect

    Dhakal, Pashupati; Tsindlekht, Menachem I; Genkin, Valery M; Ciovati, Gianluigi; Myneni, Ganapati Rao

    2013-09-01

    In an attempt to correlate the performance of superconducting radiofrequency cavities made of niobium with the superconducting properties, we present the results of the magnetization and ac susceptibility of the niobium used in the superconducting radiofrequency cavity fabrication. The samples were subjected to buffer chemical polishing (BCP) surface and high temperature heat treatments, typically applied to the cavities fabrications. The analysis of the results show the different surface and bulk ac conductivity for the samples subjected to BCP and heat treatment. Furthermore, the RF surface impedance is measured on the sample using a TE011 microwave cavity for a comparison to the low frequency measurements.

  15. 47 CFR 15.315 - Conducted limits.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 47 Telecommunication 1 2010-10-01 2010-10-01 false Conducted limits. 15.315 Section 15.315... Communications Service Devices § 15.315 Conducted limits. An unlicensed PCS device that is designed to be connected to the public utility (AC) power line must meet the limits specified in § 15.207....

  16. Spectrum of Fascicular Arrhythmias.

    PubMed

    Sung, Raphael; Scheinman, Melvin

    2016-09-01

    Fascicular arrhythmias encompass a wide spectrum of ventricular arrhythmias that depend on the specialized conduction system of the right and left ventricles. These arrhythmias include premature ventricular complexes, monomorphic ventricular tachycardia, polymorphic ventricular tachycardia, and ventricular fibrillation. These arrhythmias may be organized by mechanism, including intrafascicular reentry, interfascicular reentry, and focal. Mapping and ablation of the fascicular system can result in high cure rates of debilitating and potentially life-threatening arrhythmias. When approaching these arrhythmias, careful consideration of the structure of the His Purkinje system as well as their electrophysiologic properties may help guide even the most complex of arrhythmias.

  17. Synergistic interactions between Cry1Ac and natural cotton defenses limit survival of Cry1Ac-resistant Helicoverpa zea (Lepidoptera: Noctuidae) on Bt cotton.

    PubMed

    Anilkumar, Konasale J; Sivasupramaniam, Sakuntala; Head, Graham; Orth, Robert; Van Santen, Edzard; Moar, William J

    2009-07-01

    Larvae of the bollworm Helicoverpa zea (Boddie) show some tolerance to Bacillus thuringiensis (Bt) Cry1Ac, and can survive on Cry1Ac-expressing Bt cotton, which should increase resistance development concerns. However, field-evolved resistance has not yet been observed. In a previous study, a population of H. zea was selected for stable resistance to Cry1Ac toxin. In the present study, we determined in laboratory bioassays if larvae of the Cry1Ac toxin-resistant H. zea population show higher survival rates on field-cultivated Bt cotton squares (= flower buds) collected prebloom-bloom than susceptible H. zea. Our results show that Cry1Ac toxin-resistant H. zea cannot complete larval development on Cry1Ac-expressing Bt cotton, despite being more than 150-fold resistant to Cry1Ac toxin and able to survive until pupation on Cry1Ac toxin concentrations greater than present in Bt cotton squares. Since mortality observed for Cry1Ac-resistant H. zea on Bt cotton was higher than expected, we investigated whether Cry1Ac interacts with gossypol and or other compounds offered with cotton powder in artificial diet. Diet incorporation bioassays were conducted with Cry1Ac toxin alone, and with gossypol and 4% cotton powder in the presence and absence of Cry1Ac. Cry1Ac toxin was significantly more lethal to susceptible H. zea than to resistant H. zea, but no difference in susceptibility to gossypol was observed between strains. However, combinations of Cry1Ac with gossypol or cotton powder were synergistic against resistant, but not against susceptible H. zea. Gossypol concentrations in individual larvae showed no significant differences between insect strains, or between larvae fed gossypol alone vs. those fed gossypol plus Cry1Ac. These results may help explain the inability of Cry1Ac-resistant H. zea to complete development on Bt cotton, and the absence of field-evolved resistance to Bt cotton by this pest.

  18. Electrical conductivity of polyazomethine/fullerene C60 nanocomposites

    NASA Astrophysics Data System (ADS)

    Bronnikov, Sergei; Podshivalov, Aleksandr; Kostromin, Sergei; Asandulesa, Mihai; Cozan, Vasile

    2017-02-01

    We prepared the polyazomethine/fullerene C60 nanocomposites varying in C60 loading. With a broadband dielectric relaxation spectrometer, we measured their electrical conductivity σm being a sum of dc conductivity σdc and ac conductivity σac. A small C60 content (0.25 and 0.5 wt.%) was shown to decrease σdc, whereas a larger amount of C60 (2.5 wt.%) was found to increase σdc of the nanocomposite. The temperature dependences of σac were described with the Arrhenius equation, while the frequency dependences of σac were characterized with a power function. The correlated barrier hopping was accepted as the most suitable mechanism to explain the σac behavior of the nanocomposites.

  19. Occurrence of electrical percolation threshold and observation of phase transition in chitosan(1- x):AgI x (0.05 ≤ x ≤ 0.2)-based ion-conducting solid polymer composites

    NASA Astrophysics Data System (ADS)

    Aziz, Shujahadeen B.

    2016-07-01

    This paper reports on the investigation of electrical percolation threshold and ion transport mechanism for ion-conducting solid polymer composites based on chitosan. The composite samples were prepared by solution cast technique. The result of DC conductivity versus percolation threshold (Φ^{ - 1/3} ) confirmed that at low AgI concentration, the tunneling effect governs ionic conduction mechanism. Nevertheless, at high filler concentration, the DC conductivity showed a plateau behavior. The DC conductivity as a function of reciprocal temperature revealed that the ion conduction mechanism is slightly temperature dependent and the ion-ion correlational effect is dominant. A steep increase in DC conductivity above 323 K is observed, which indicated the existence of some phase transition near the beta (β)-phase. The drop of DC conductivity at high temperatures is anticipated from the impedance plots. The AC conductivity spectrum exhibited three distinct regions at low temperatures. The high-frequency regions of AC conductivity spectra were almost temperature independent at low temperatures (303-323 K) and obeyed the Jonscher's power law. The variation in frequency exponent versus temperature reveals that ion conduction mechanism follows QMT and CBH models at low and high temperatures, respectively. The valuable achievement of this work is that the temperature dependence of DC conductivity and the frequency exponent ( s) is correlated to interpret the Ag+ ion dynamic and ion-ion correlational effect. The Argand plots were used to explain the relaxation processes.

  20. ACS from development to operations

    NASA Astrophysics Data System (ADS)

    Caproni, Alessandro; Colomer, Pau; Jeram, Bogdan; Sommer, Heiko; Chiozzi, Gianluca; Mañas, Miguel M.

    2016-08-01

    The ALMA Common Software (ACS), provides the infrastructure of the distributed software system of ALMA and other projects. ACS, built on top of CORBA and Data Distribution Service (DDS) middleware, is based on a Component- Container paradigm and hides the complexity of the middleware allowing the developer to focus on domain specific issues. The transition of the ALMA observatory from construction to operations brings with it that ACS effort focuses primarily on scalability, stability and robustness rather than on new features. The transition came together with a shorter release cycle and a more extensive testing. For scalability, the most problematic area has been the CORBA notification service, used to implement the publisher subscriber pattern because of the asynchronous nature of the paradigm: a lot of effort has been spent to improve its stability and recovery from run time errors. The original bulk data mechanism, implemented using the CORBA Audio/Video Streaming Service, showed its limitations and has been replaced with a more performant and scalable DDS implementation. Operational needs showed soon the difference between releases cycles for Online software (i.e. used during observations) and Offline software, which requires much more frequent releases. This paper attempts to describe the impact the transition from construction to operations had on ACS, the solution adopted so far and a look into future evolution.

  1. Simple Equipment for Imaging AC.

    ERIC Educational Resources Information Center

    Kamata, Masahiro; Anayama, Takayuki

    2003-01-01

    Presents an effective way to demonstrate the difference between direct current and alternating current using red and green LEDs. Describes how to make a tool that shows how an AC voltage changes with time using the afterimage effect of the LEDs. (Author/NB)

  2. On the Absolutely Continuous Spectrum of Stark Operators

    NASA Astrophysics Data System (ADS)

    Perelman, Galina

    The stability of the absolutely continuous spectrum of the one-dimensional Stark operator under perturbations of the potential is discussed. The focus is on proving this stability under minimal assumptions on smoothness of the perturbation. A general criterion is presented together with some applications. These include the case of periodic perturbations where we show that any perturbation vL1()∩H-1/2() preserves the a.c. spectrum.

  3. Electrothermally driven flows in ac electrowetting.

    PubMed

    García-Sánchez, Pablo; Ramos, Antonio; Mugele, Frieder

    2010-01-01

    Mixing within sessile drops can be enhanced by generating internal flow patterns using ac electrowetting. While for low ac frequencies, the flow patterns have been attributed to oscillations of the drop surface, we provide here the driving mechanism of the hitherto unexplained high-frequency flows. We show that: (1) the electric field in the liquid bulk becomes important, leading to energy dissipation due to Joule heating and a temperature increase of several degrees Celsius, and (2) the fluid flow at these frequencies is generated by electrothermal effect, i.e., gradients in temperature give rise to gradients in conductivity and permittivity, the electric field acting on these inhomogeneities induces an electrical body force that generates the flow. We solved numerically the equations for the electric, temperature and flow fields. The temperature is obtained from a convection-diffusion equation where Joule heating is introduced as a source term. From the solution of the electric field and the temperature, we compute the electrical force that acts as a body force in Stokes equations. Our numerical results agree with previous experimental observations.

  4. AC impedance analysis of polypyrrole thin films

    NASA Technical Reports Server (NTRS)

    Penner, Reginald M.; Martin, Charles R.

    1987-01-01

    The AC impedance spectra of thin polypyrrole films were obtained at open circuit potentials from -0.4 to 0.4 V vs SCE. Two limiting cases are discussed for which simplified equivalent circuits are applicable. At very positive potentials, the predominantly nonfaradaic AC impedance of polypyrrole is very similar to that observed previously for finite porous metallic films. Modeling of the data with the appropriate equivalent circuit permits effective pore diameter and pore number densities of the oxidized film to be estimated. At potentials from -0.4 to -0.3 V, the polypyrrole film is essentially nonelectronically conductive and diffusion of polymer oxidized sites with their associated counterions can be assumed to be linear from the film/substrate electrode interface. The equivalent circuit for the polypyrrole film at these potentials is that previously described for metal oxide, lithium intercalation thin films. Using this model, counterion diffusion coefficients are determined for both semi-infinite and finite diffusion domains. In addition, the limiting low frequency resistance and capacitance of the polypyrrole thin fims was determined and compared to that obtained previously for thicker films of the polymer. The origin of the observed potential dependence of these low frequency circuit components is discussed.

  5. Microwave conductance of aligned multiwall carbon nanotube textile sheets

    NASA Astrophysics Data System (ADS)

    Brown, Brian L.; Bykova, Julia S.; Howard, Austin R.; Zakhidov, Anvar A.; Shaner, Eric A.; Lee, Mark

    2014-12-01

    Multiwall carbon nanotube (MWNT) sheets are a class of nanomaterial-based multifunctional textile with potentially useful microwave properties. To understand better the microwave electrodynamics, complex AC conductance measurements from 0.01 to 50 GHz were made on sheets of highly aligned MWNTs with the alignment texture both parallel and perpendicular to the microwave electric field polarization. In both orientations, the AC conductance is modeled to first order by a parallel frequency-independent conductance and capacitance with no inductive contribution. This is consistent with low-frequency diffusive Drude AC conduction up to 50 GHz, in contrast to the "universal disorder" AC conduction reported in many types of single-wall nanotube materials.

  6. Electrical Conductivity.

    ERIC Educational Resources Information Center

    Hershey, David R.; Sand, Susan

    1993-01-01

    Explains how electrical conductivity (EC) can be used to measure ion concentration in solutions. Describes instrumentation for the measurement, temperature dependence and EC, and the EC of common substances. (PR)

  7. ac-resistance-measuring instrument

    SciTech Connect

    Hof, P.J.

    1981-04-22

    An auto-ranging ac resistance measuring instrument for remote measurement of the resistance of an electrical device or circuit connected to the instrument includes a signal generator which generates an ac excitation signal for application to a load, including the device and the transmission line, a monitoring circuit which provides a digitally encoded signal representing the voltage across the load, and a microprocessor which operates under program control to provide an auto-ranging function by which range resistance is connected in circuit with the load to limit the load voltage to an acceptable range for the instrument, and an auto-compensating function by which compensating capacitance is connected in shunt with the range resistance to compensate for the effects of line capacitance.

  8. Simultaneous distribution of AC and DC power

    DOEpatents

    Polese, Luigi Gentile

    2015-09-15

    A system and method for the transport and distribution of both AC (alternating current) power and DC (direct current) power over wiring infrastructure normally used for distributing AC power only, for example, residential and/or commercial buildings' electrical wires is disclosed and taught. The system and method permits the combining of AC and DC power sources and the simultaneous distribution of the resulting power over the same wiring. At the utilization site a complementary device permits the separation of the DC power from the AC power and their reconstruction, for use in conventional AC-only and DC-only devices.

  9. The Absorption Spectrum of Iodine Vapour

    ERIC Educational Resources Information Center

    Tetlow, K. S.

    1972-01-01

    A laboratory experiment is described which presents some molecular parameters of iodine molecule by studying iodine spectrum. Points out this experiment can be conducted by sixth form students in high school laboratories. (PS)

  10. Reliable 100 kbps low-voltage ac powerline communications

    NASA Astrophysics Data System (ADS)

    Ladas, Chris; Propp, Michael

    1995-12-01

    Achieving reliable, 100 kbps powerline communications on the low voltage, AC powerlines has been realized by combining new techniques in spread spectrum technology with a robust, powerline specific protocol. This approach enables reliable, high speed data networking on the electrically hostile, low voltage powerline. Applications for the new technology include utility DA/DSM (distribution automation/demand side management), intraoffice LANs, powerline based telephony, and industrial data networking applications. This technological advancement was made possible through statistical modeling of the low voltage powerline, and developing unique spread spectrum and protocol techniques specific to the resulting powerline environment. The technology has been implemented as a highly integrated, CMOS chip set, allowing straightforward integration into OEM systems and products.

  11. AC Josephson effect applications in microwave systems

    NASA Astrophysics Data System (ADS)

    Larkin, Serguey Y.

    1996-12-01

    analysis allow to get the picture of temperature distribution along the plasma cord diameter in accordance with dynamics of thermonuclear process development. Modem raclioastronomic research gives scientists the unique information on the world tructure. It is also necessary to analyze Space microwave radiation providing exclusive sensitivity of the equipment. In both cases equipment is required to be superwide band, to have high sensitivity and ability to operate at more than 300 GHz frequencies. Today all these requirements are met by the devices using the ac Josephson effect. The Josephson junctions are used as an active transforming element in such devices. At the end of 20 century the sphere of their utilization embraces medicine, communications, radiophysics, space exploration, ecology, military use, etc. The State Research Center "Fonon" ( SRC "Fonon") of the State Committee on Science and Technology of Ukraine was founded in 1991. The main aim of its creation was to concentrate the scientific and financial efforts for development and production of unique devices based on the results of fundamental study in physics of high T superconductivity. First of all we were interested in technological research on the obtaining of low impedance Josephson junctions out of the High T thin films. Using such junctions in combination with our original techniques developed in our Center we have succeed in creating the following new generation equipment: industrial set-up of the frequency meter in the range of 60 ... 600 GHz; experimental set-up of the spectrum analyzer operating in the range of 50 250 GHz; experimental model of radiometric receiver in 180...260 GHz range. All the above devices are based on the using ac Josephson effect for the receiving and processing mm- and submm- microwave signals.

  12. Appropriate Conduct

    ERIC Educational Resources Information Center

    Di Lullo, Louis

    2004-01-01

    Many years ago when the author assumed the role of assistant principal for school climate, discipline, and attendance, he inherited many school policies and guidelines that were outdated, unfair, and without merit in the current school climate. Because the school conduct code had not been revised since the school opened in 1960, many of the…

  13. Dynamics of lamin A/C in porcine embryos produced by nuclear transfer.

    PubMed

    Lee, Kiho; Fodor, William L; Machaty, Zoltan

    2007-09-01

    This study was conducted to investigate the presence of lamin A/C in porcine nuclear transfer embryos and to determine whether lamin A/C can serve as a potential marker for nuclear reprogramming. First, lamin A/C was studied in oocytes and embryos produced by fertilization or parthenogenetic oocyte activation. We found that lamin A/C was present in the nuclear lamina of oocytes at the germinal vesicle stage while it was absent in mature oocytes. Lamin A/C was detected throughout preimplantation development in both in vivo-derived and parthenogenetic embryos. Incubation of the activated oocytes in the presence of alpha-amanitin (an inhibitor of RNA polymerase II), or cycloheximide (a protein synthesis inhibitor) did not perturb lamin A/C assembly, indicating that the assembly resulted from solubilized lamins dispersed in the cytoplasm. In nuclear transfer embryos, the lamin A/C signal that had previously been identified in fibroblast nuclei disappeared soon after fusion. It became detectable again after the formation of the pronucleus-like structure, and all nuclear transfer embryos displayed lamin A/C staining during early development. Olfactory bulb progenitor cells lacked lamin A/C; however, when such cells were fused with enucleated oocytes, the newly formed nuclear envelopes stained positive for lamin A/C. These findings suggest that recipient oocytes remodel the donor nuclei using type A lamins dispersed in the ooplasm. The results also indicate that lamin A/C is present in the nuclear envelope of pig oocytes and early embryos and unlike in some other species, its presence after nuclear transfer is not an indicator of erroneous reprogramming.

  14. Rotational spectrum of tryptophan

    NASA Astrophysics Data System (ADS)

    Sanz, M. Eugenia; Cabezas, Carlos; Mata, Santiago; Alonso, Josè L.

    2014-05-01

    The rotational spectrum of the natural amino acid tryptophan has been observed for the first time using a combination of laser ablation, molecular beams, and Fourier transform microwave spectroscopy. Independent analysis of the rotational spectra of individual conformers has conducted to a definitive identification of two different conformers of tryptophan, with one of the observed conformers never reported before. The analysis of the 14N nuclear quadrupole coupling constants is of particular significance since it allows discrimination between structures, thus providing structural information on the orientation of the amino group. Both observed conformers are stabilized by an O-H...N hydrogen bond in the side chain and a N-H...π interaction forming a chain that reinforce the strength of hydrogen bonds through cooperative effects.

  15. Rotational spectrum of tryptophan

    SciTech Connect

    Sanz, M. Eugenia Cabezas, Carlos Mata, Santiago Alonso, Josè L.

    2014-05-28

    The rotational spectrum of the natural amino acid tryptophan has been observed for the first time using a combination of laser ablation, molecular beams, and Fourier transform microwave spectroscopy. Independent analysis of the rotational spectra of individual conformers has conducted to a definitive identification of two different conformers of tryptophan, with one of the observed conformers never reported before. The analysis of the {sup 14}N nuclear quadrupole coupling constants is of particular significance since it allows discrimination between structures, thus providing structural information on the orientation of the amino group. Both observed conformers are stabilized by an O–H···N hydrogen bond in the side chain and a N–H···π interaction forming a chain that reinforce the strength of hydrogen bonds through cooperative effects.

  16. Determination of the spectrum of low molecular mass organic acids in urine by capillary electrophoresis with contactless conductivity and ultraviolet photometric detection--an efficient tool for monitoring of inborn metabolic disorders.

    PubMed

    Tůma, Petr; Samcová, Eva; Stulík, Karel

    2011-01-24

    A mixture of 29 organic acids (OAs) occurring in urine was analyzed by capillary electrophoresis (CE) with capacitively coupled contactless conductivity detection (C(4)D) and UV photometric detection. The optimized analytical system involved a 100 cm long polyacrylamide-coated capillary (50 μm i.d.) and the background electrolyte of 20mM 2-morpholinoethanesulfonic acid (MES)/NaOH+10% (v/v) methanol, pH 6.0 (pH is related to the 20mM MES/NaOH buffer in water). The LOD values obtained by C(4)D for the OAs which do not absorb UV radiation range from 0.6 μM (oxalic acid) to 6.8 μM (pyruvic acid); those obtained by UV photometry for the remaining OAs range from 2.9 μM (5-hydroxy-3-indoleacetic acid) to 10.2 μM (uric acid). The repeatability of the procedure developed is characterized by the coefficients of variation, which vary between 0.3% (tartaric acid) and 0.6% (5-hydroxy-3-indoleacetic acid) for the migration time and between 1.3% (tartaric acid) and 3.5% (lactic acid) for the peak area. The procedure permitted quantitation of 20 OAs in a real urine sample and was applied to monitoring of the occurrence of the inborn metabolic fault of methylmalonic aciduria.

  17. AC Impedance Studies on Metal/Nanoporous Silicon/ p-Silicon Structures

    NASA Astrophysics Data System (ADS)

    Mabrook, M. F.; Ray, A. K.

    2017-04-01

    Alternating current (AC) impedance measurements have been performed on 10- to 15- μm thick porous silicon layers on a (100) p-type silicon ( p(+)Si) substrate with the aluminium (Al) top electrode in a sandwich configuration in the range of 20 Hz-1 MHz and in the temperature ranging between 152 K and 292 K. The ac conductivity σ ac was found to increase with frequency f according to the universal power law: σ_{{ac}} = Afs where the exponent s is a frequency and temperature-dependent quantity. A hopping process is found to be dominant at low temperatures and high frequencies, while a thermally activated free band process is responsible for conduction at higher temperatures. Capacitance is found to decrease with frequency but increase with temperature. Frequency dependence of the loss tangent is observed with a temperature-dependent minimum value.

  18. AC Impedance Studies on Metal/Nanoporous Silicon/p-Silicon Structures

    NASA Astrophysics Data System (ADS)

    Mabrook, M. F.; Ray, A. K.

    2016-11-01

    Alternating current (AC) impedance measurements have been performed on 10- to 15-μm thick porous silicon layers on a (100) p-type silicon (p(+)Si) substrate with the aluminium (Al) top electrode in a sandwich configuration in the range of 20 Hz-1 MHz and in the temperature ranging between 152 K and 292 K. The ac conductivity σ ac was found to increase with frequency f according to the universal power law: σ_{ac} = Afs where the exponent s is a frequency and temperature-dependent quantity. A hopping process is found to be dominant at low temperatures and high frequencies, while a thermally activated free band process is responsible for conduction at higher temperatures. Capacitance is found to decrease with frequency but increase with temperature. Frequency dependence of the loss tangent is observed with a temperature-dependent minimum value.

  19. New levitation scheme with AC superconducting magnet for EDS MAGLEV system

    SciTech Connect

    Kim, D.H.; Lee, J.K.; Hahn, S.Y.; Cha, G.

    1996-09-01

    This paper proposes a new magnetic levitation scheme which is able to generate levitation force for all speeds including a standstill. Auxiliary wheels which are needed in EDS MAGLEV vehicle can be eliminated. This scheme uses AC superconducting magnets to generate levitation force. In this paper, magnetic fields, forces and power dissipations generated by AC magnets moving above a conducting slab are calculated analytically. Results of calculation show characteristics of EDS system with AC magnet, such as levitation force and loss, are superior to those of EDS system with DC magnets for all speeds.

  20. ACS after SM4: On-orbit Verification of the HST Advanced Camera for Surveys Repair

    NASA Astrophysics Data System (ADS)

    Golimowski, David A.; Cheng, E. S.; Loose, M.; Sirianni, M.; Lupie, O. L.; Smith, L. J.; Arslanian, S.; Boyce, K. R.; Chapman, G.; Chiaberge, M.; Desjardins, T.; Dye, D.; Ellis, T.; Grogin, N. A.; Lim, P.; Lucas, R. A.; Maybhate, A.; Mil, K. J.; Mutchler, M.; Ricardo, R.; Scott, B.; Serrano, B.; Suchkov, A.; Waczynski, A.; Welty, A. D.; Wheeler, T.; Wilson, E.

    2010-01-01

    The newly replaced CCD electronics box (CEB-R) of the Hubble Space Telescope (HST) Advanced Camera for Surveys (ACS) features a programmable SIDECAR ASIC manufactured by Teledyne. The CEB-R not only restores the functionality of the ACS Wide Field Camera (WFC), but it allows optimization of the WFC's imaging performance via on-orbit adjustment of CCD bias and clock voltages and serial-data transmission timing. We describe the strategy, preparation, execution, and results of the ACS Optimization Campaign, an unprecedented on-orbit extension of ground-based integration and testing that was conducted during the HST Servicing Mission Observatory Verification period.

  1. An ac electroosmosis device for the detection of bioparticles with piezoresistive microcantilever sensors

    NASA Astrophysics Data System (ADS)

    Arefin, Md Shamsul; Porter, Timothy L.

    2012-03-01

    This work reports on the behavior of piezoresistive microcantilever sensors under optimizing conditions of ac electroosmotic enhancement. Piezoresistive microcantilevers are used as sensor elements for detection of concentrated bio-particles. Without preconcentrating the samples, using ac electroosmosis, these bio-particles have been manipulated onto the piezoresistive microcantilever. A piezoresistive microcantilever senses the dimensional changes upon particle exposure as a resistance change. This paper represents the integration of ac electroosmosis with a piezoresistive micro-cantilever sensor for the detection of bio-particles. A working prototype is presented here, and the experiments are conducted on Herpes Simplex type-1 virus (HSV-1) and Escherichia Coli (E. coli) bacteria.

  2. Effect of the magnetic material on AC losses in HTS conductors in AC magnetic field carrying AC transport current

    NASA Astrophysics Data System (ADS)

    Wan, Xing-Xing; Huang, Chen-Guang; Yong, Hua-Dong; Zhou, You-He

    2015-11-01

    This paper presents an investigation on the AC losses in several typical superconducting composite conductors using the H-formulation model. A single superconducting strip with ferromagnetic substrate or cores and a stack of coated conductors with ferromagnetic substrates are studied. We consider all the coated conductors carrying AC transport currents and simultaneously exposed to perpendicular AC magnetic fields. The influences of the amplitude, frequency, phase difference and ferromagnetic materials on the AC losses are investigated. The results show that the magnetization losses of single strip and stacked strips have similar characteristics. The ferromagnetic substrate can increase the magnetization loss at low magnetic field, and decrease the loss at high magnetic field. The ferromagnetic substrate can obviously increase the transport loss in stacked strips. The trends of total AC losses of single strip and stacked strips are similar when they are carrying current or exposed to a perpendicular magnetic field. The effect of the frequency on the total AC losses of single strip is related to the amplitude of magnetic field. The AC losses decrease with increasing frequency in low magnetic field region while increase in high magnetic field region. As the phase difference changes, there is a periodic variation for the AC losses. Moreover, when the strip is under only the transport current and magnetic field, the ferromagnetic cores will increase the AC losses for large transport current or field.

  3. Abscisic Acid Antagonizes Ethylene Production through the ABI4-Mediated Transcriptional Repression of ACS4 and ACS8 in Arabidopsis.

    PubMed

    Dong, Zhijun; Yu, Yanwen; Li, Shenghui; Wang, Juan; Tang, Saijun; Huang, Rongfeng

    2016-01-04

    Increasing evidence has revealed that abscisic acid (ABA) negatively modulates ethylene biosynthesis, although the underlying mechanism remains unclear. To identify the factors involved, we conducted a screen for ABA-insensitive mutants with altered ethylene production in Arabidopsis. A dominant allele of ABI4, abi4-152, which produces a putative protein with a 16-amino-acid truncation at the C-terminus of ABI4, reduces ethylene production. By contrast, two recessive knockout alleles of ABI4, abi4-102 and abi4-103, result in increased ethylene evolution, indicating that ABI4 negatively regulates ethylene production. Further analyses showed that expression of the ethylene biosynthesis genes ACS4, ACS8, and ACO2 was significantly decreased in abi4-152 but increased in the knockout mutants, with partial dependence on ABA. Chromatin immunoprecipitation-quantitative PCR assays showed that ABI4 directly binds the promoters of these ethylene biosynthesis genes and that ABA enhances this interaction. A fusion protein containing the truncated ABI4-152 peptide accumulated to higher levels than its full-length counterpart in transgenic plants, suggesting that ABI4 is destabilized by its C terminus. Therefore, our results demonstrate that ABA negatively regulates ethylene production through ABI4-mediated transcriptional repression of the ethylene biosynthesis genes ACS4 and ACS8 in Arabidopsis.

  4. Optical conductivity from pair density waves

    NASA Astrophysics Data System (ADS)

    Dai, Zhehao; Lee, Patrick A.

    2017-01-01

    We present a theory of optical conductivity in systems with finite-momentum Cooper pairs. In contrast to the BCS pairing where ac conductivity is purely imaginary in the clean limit, there is nonzero ac absorption across the superconducting gap for finite-momentum pairing if we break the Galilean symmetry explicitly in the electronic Hamiltonian. Vertex correction is crucial for maintaining the gauge invariance in the mean-field formalism and dramatically changes the optical conductivity in the direction of the pairing momentum. We carried out a self-consistent calculation and gave an explicit formula for optical conductivity in a simple case. This result applies to the Fulde-Ferrell-Larkin-Ovchinnikov state and candidates with pair density waves proposed for high-Tc cuprates. It may help detect pair density waves and determine the pairing gap as well as the direction of the pairing momentum in experiments.

  5. Temperature dependence of dc electrical conductivity of activated carbon-metal oxide nanocomposites. Some insight into conduction mechanisms

    NASA Astrophysics Data System (ADS)

    Barroso-Bogeat, Adrián; Alexandre-Franco, María; Fernández-González, Carmen; Sánchez-González, José; Gómez-Serrano, Vicente

    2015-12-01

    From a commercial activated carbon (AC) and six metal oxide (Al2O3, Fe2O3, SnO2, TiO2, WO3 and ZnO) precursors, two series of AC-metal oxide nanocomposites are prepared by wet impregnation, oven-drying at 120 °C, and subsequent heat treatment at 200 or 850 °C in inert atmosphere. The temperature-dependent dc electrical conductivity of AC and the as-prepared nanocomposites is measured from room temperature up to ca. 200 °C in air atmosphere by the four-probe method. The decrease in conductivity for the hybrid materials as compared to AC is the result of a complex interplay between several factors, including not only the intrinsic conductivity, crystallite size, content and chemical nature of the supported nanoparticles, which ultimately depend on the precursor and heat treatment temperature, but also the adsorption of oxygen and water from the surrounding atmosphere. The conductivity data are discussed in terms of a thermally activated process. In this regard, both AC and the prepared nanocomposites behave as semiconductors, and the temperature-dependent conductivity data have been interpreted on the basis of the classical model proposed by Mott and Davis. Because of its high content of heteroatoms, AC may be considered as a heavily doped semiconductor, so that conduction of thermally excited carriers via acceptor or donor levels is expected to be the dominant mechanism. The activation energies for the hybrid materials suggest that the supported metal oxide nanoparticles strongly modify the electronic band structure of AC by introducing new trap levels in different positions along its band gap. Furthermore, the thermally activated conduction process satisfies the Meyer-Neldel rule, which is likely connected with the shift of the Fermi level due to the introduction of the different metal oxide nanoparticles in the AC matrix.

  6. ACS PSF Variations with Temperatures

    NASA Astrophysics Data System (ADS)

    Sahu, Kailash C.; Lallo, Matt; Makidon, Russ

    2007-09-01

    We have used the HST ACS/WFC observations of a Galactic bulge field taken over a continuous interval of 7 days (Prop 9750) to investigate the possible dependence of the ACS focus with the external temperatures. This dataset allows us to investigate possible focus variations over timescales of a few hours to a few days. The engineering data related to the external temperatures for this duration show that the maximum temperature change occurred over the first 1.5 days. Among all the different temperatures recorded, the truss diametric differential and the truss axial temperatures are the only two temperatures which have the same timescale of variation as the PSFwidth variations. The PSF-widths also strongly correlate with these two temperatures during this time interval. We empirically fit the PSF-width variations with these 2 temperature sensor values. This suggests that the focus has a similar dependence, and we recommend that this finding be followed up with the determination of actual focus values to check if the focus values indeed have the same correlation. If so, the temperature data can be useful in estimating the focus values, which can then be used to predict the PSFs to a first order.

  7. RHIC spin flipper AC dipole controller

    SciTech Connect

    Oddo, P.; Bai, M.; Dawson, C.; Gassner, D.; Harvey, M.; Hayes, T.; Mernick, K.; Minty, M.; Roser, T.; Severino, F.; Smith, K.

    2011-03-28

    The RHIC Spin Flipper's five high-Q AC dipoles which are driven by a swept frequency waveform require precise control of phase and amplitude during the sweep. This control is achieved using FPGA based feedback controllers. Multiple feedback loops are used to and dynamically tune the magnets. The current implementation and results will be presented. Work on a new spin flipper for RHIC (Relativistic Heavy Ion Collider) incorporating multiple dynamically tuned high-Q AC-dipoles has been developed for RHIC spin-physics experiments. A spin flipper is needed to cancel systematic errors by reversing the spin direction of the two colliding beams multiple times during a store. The spin flipper system consists of four DC-dipole magnets (spin rotators) and five AC-dipole magnets. Multiple AC-dipoles are needed to localize the driven coherent betatron oscillation inside the spin flipper. Operationally the AC-dipoles form two swept frequency bumps that minimize the effect of the AC-dipole dipoles outside of the spin flipper. Both AC bumps operate at the same frequency, but are phase shifted from each other. The AC-dipoles therefore require precise control over amplitude and phase making the implementation of the AC-dipole controller the central challenge.

  8. The diagnostic performance of serum MUC5AC for cholangiocarcinoma

    PubMed Central

    Xuan, Ji; Li, Jing; Zhou, Zhirui; Zhou, Renrong; Xu, Huabing; Wen, Wei

    2016-01-01

    Abstract Specific diagnostic biomarker for cholangiocarcinoma (CCA) has been lacking. This systematic review and meta-analysis was performed aiming to investigate serum MUC5AC's diagnostic performance on CCA. Studies investigating serum MUC5AC's diagnostic value on CCA were retrieved from Pubmed, Embase, and Cochrane Library. The methodology quality of included studies was assessed according to QUADAS-2. Diagnostic 2 × 2 table was extracted from each eligible study, Meta-disc 1.4 was used for statistical analysis, data synthesis was done using a random-effects model. Subgroup analyses were conducted according to region and array method. Six eligible studies were identified, a total of 1213 patients were involved in the meta-analysis. The AUC on SROC was 0.9138, and the Q∗ was 8463. The pooled sensitivity, specificity, positive likelihood ratio, negative likelihood ratio, and diagnostic odds ratio (DOR) were 0.69 (95% CI: 0.65–0.73), 0.93 (95% CI: 0.91–0.95), 8.99 (95% CI: 5.65–14.30), 0.33 (95% CI: 0.24–0.46), and 33.98 (95% CI: 20.12–57.40), respectively. Targeting MUC5AC's epitope has a higher pooled sensitivity than targeting MUC5AC protein (0.77 vs 0.63). There was substantial cross-study heterogeneity. Serum MUC5AC might be potentially used as a surrogate marker in the diagnosis of CCA. However, the appropriate array method and the optimum cut-off value are yet to be decided. PMID:27310944

  9. Identify bipolar spectrum disorders.

    PubMed

    Mynatt, Sarah; Cunningham, Patricia; Manning, J Sloan

    2002-06-01

    Patients with bipolar spectrum disorders commonly present with depressive symptoms to primary care clinicians. This article details bipolar spectrum disorder assessment, treatment, and treatment response. By intervening early in the course of depressive and hypomanic episodes, you can help decrease the morbidity and suffering associated with bipolar spectrum disorders.

  10. Performance testing of the AC propulsion ELX electric vehicle

    SciTech Connect

    Kramer, W.E.; MacDowall, R.D.; Burke, A.F.

    1994-06-01

    Performance testing of the AC Propulsion ELX electric vehicle is described. Test data are presented and analyzed. The ELX vehicle is the first of a series of electric vehicles of interest to the California Air Resources Board. The test series is being conducted under a Cooperative Research and Development Agreement (CRADA) between the US Department of energy and the California Air Resources Board. The tests which were conducted showed that the AC Propulsion ELX electric vehicle has exceptional acceleration and range performance. when the vehicle`s battery was fully charged, the vehicle can accelerate from 0 to 96 km/h in about 10 seconds. Energy consumption and range tests using consecutive FUDS and HWFET Driving cycles (the all-electric cycle) indicate that the energy economy of the AC Propulsion ELX electric vehicle with regenerative braking is 97 W{center_dot}h/km, with a range of 153 km (95 miles). Computer simulations performed using the SIMPLEV Program indicate that the vehicle would have a range of 327 km (203 miles) on the all-electric cycle if the lead acid batteries were replaced with NiMH batteries having an energy density of 67 W{center_dot}h/kg. Comparisons of FUDS test data with and without regenerative braking indicated that regenerative braking reduced the energy consumption of the ELX vehicle by approximately 25%.

  11. An AC electrokinetic method for enhanced detection of DNA nanoparticles.

    PubMed

    Krishnan, Rajaram; Heller, Michael J

    2009-04-01

    In biomedical research and diagnostics it is a challenge to isolate and detect low levels of nanoparticles and nanoscale biomarkers in blood and other biological samples. While highly sensitive epifluorescent microscope systems are available for ultra low level detection, the isolation of the specific entities from large sample volumes is often the bigger limitation. AC electrokinetic techniques like dielectrophoresis (DEP) offer an attractive mechanism for specifically concentrating nanoparticles into microscopic locations. Unfortunately, DEP requires significant sample dilution thus making the technology unsuitable for biological applications. Using a microelectrode array device, special conditions have been found for the separation of hmw-DNA and nanoparticles under high conductance (ionic strength) conditions. At AC frequencies in the 3000-10 000 Hz range, 10 mum microspheres and human T lymphocytes can be isolated into the DEP low field regions, while hmw-DNA and nanoparticles can be concentrated into microscopic high field regions for subsequent detection using an epifluorescent system.

  12. Conducting a thermal conductivity survey

    NASA Technical Reports Server (NTRS)

    Allen, P. B.

    1985-01-01

    A physically transparent approximate theory of phonon decay rates is presented starting from a pair potential model of the interatomic forces in an insulator or semiconductor. The theory applies in the classical regime and relates the 3-phonon decay rate to the third derivative of the pair potential. Phonon dispersion relations do not need to be calculated, as sum rules relate all the needed quantities directly to the pair potential. The Brillouin zone averaged phonon lifetime turns out to involve a dimensionless measure of the anharmonicity multiplied by an effective density of states for 3-phonon decay. Results are given for rare gas and alkali halide crystals. For rare gases, the results are in good agreement with more elaborate perturbation calculations. Comparison to experimental data on phonon linewidths and thermal conductivity are made.

  13. Roebel assembled coated conductor cables (RACC): Ac-Losses and current carrying potential

    NASA Astrophysics Data System (ADS)

    Frank, A.; Heller, R.; Goldacker, W.; Kling, A.; Schmidt, C.

    2008-02-01

    Low ac-loss HTS cables for transport currents well above 1 kA are required for application in transformers and generators and are taken into consideration for future generations of fusion reactor coils. Coated conductors (CC) are suitable candidates for high field application at an operation temperature in the range 50-77 K. Ac-field applications require cables with low ac-losses and hence twisting of the individual strands. We solved this problem using the Roebel technique. Short lengths of Roebel bar cables were prepared from industrial DyBCO and YBCO-CC. Meander shaped tapes of 4 or 5 mm width with twist pitches of 123 or 127 mm were cut from the 10 or 12 mm wide CC tapes using a specially designed tool. Eleven or twelve of these strands were assembled to a cable. The electrical and mechanical connection of the tapes was achieved using a silver powder filled conductive epoxy resin. Ac-losses of a short sample in an external ac-field were measured as a function of frequency and field amplitude as well as the coupling current decay time constant. We discuss the results in terms of available theories and compare measured time constants in transverse field with measured coupling losses. Finally the potential of this cable type for ac-use is discussed with respect to ac-losses and current carrying capability.

  14. Experimental Investigation of Electrical Conductivity and Permittivity of SC-TiO 2 -EG Nanofluids.

    PubMed

    Fal, Jacek; Barylyak, Adriana; Besaha, Khrystyna; Bobitski, Yaroslav V; Cholewa, Marian; Zawlik, Izabela; Szmuc, Kamil; Cebulski, Józef; Żyła, Gaweł

    2016-12-01

    The paper presents experimental studies of dielectric properties of nanofluids based on ethylene glycol and SC-TiO2 nanoparticles with average size of 15-40 nm with various mass concentrations. The dielectric permittivity both real part and imaginary part as a function of temperature and frequency were measured. Also, dependence ac conductivity on frequency, temperature, and mass concentration were investigated. Based on the curves of ac conductivity, dc conductivity was calculated, and 400 % enhancement in dc conductivity was exposed.

  15. Experimental Investigation of Electrical Conductivity and Permittivity of SC-TiO 2 -EG Nanofluids

    NASA Astrophysics Data System (ADS)

    Fal, Jacek; Barylyak, Adriana; Besaha, Khrystyna; Bobitski, Yaroslav V.; Cholewa, Marian; Zawlik, Izabela; Szmuc, Kamil; Cebulski, Józef; żyła, Gaweł

    2016-08-01

    The paper presents experimental studies of dielectric properties of nanofluids based on ethylene glycol and SC-TiO2 nanoparticles with average size of 15-40 nm with various mass concentrations. The dielectric permittivity both real part and imaginary part as a function of temperature and frequency were measured. Also, dependence ac conductivity on frequency, temperature, and mass concentration were investigated. Based on the curves of ac conductivity, dc conductivity was calculated, and 400 % enhancement in dc conductivity was exposed.

  16. Calibration-free electrical conductivity measurements for highly conductive slags

    SciTech Connect

    MACDONALD,CHRISTOPHER J.; GAO,HUANG; PAL,UDAY B.; VAN DEN AVYLE,JAMES A.; MELGAARD,DAVID K.

    2000-05-01

    This research involves the measurement of the electrical conductivity (K) for the ESR (electroslag remelting) slag (60 wt.% CaF{sub 2} - 20 wt.% CaO - 20 wt.% Al{sub 2}O{sub 3}) used in the decontamination of radioactive stainless steel. The electrical conductivity is measured with an improved high-accuracy-height-differential technique that requires no calibration. This method consists of making continuous AC impedance measurements over several successive depth increments of the coaxial cylindrical electrodes in the ESR slag. The electrical conductivity is then calculated from the slope of the plot of inverse impedance versus the depth of the electrodes in the slag. The improvements on the existing technique include an increased electrochemical cell geometry and the capability of measuring high precision depth increments and the associated impedances. These improvements allow this technique to be used for measuring the electrical conductivity of highly conductive slags such as the ESR slag. The volatilization rate and the volatile species of the ESR slag measured through thermogravimetric (TG) and mass spectroscopy analysis, respectively, reveal that the ESR slag composition essentially remains the same throughout the electrical conductivity experiments.

  17. Evaluation of the in vivo genotoxicity of Allura Red AC (Food Red No. 40).

    PubMed

    Honma, Masamitsu

    2015-10-01

    Allura Red AC (Food Red No. 40) is a red azo dye that is used for food coloring in beverage and confectionary products. However, its genotoxic properties remain controversial. To clarify the in vivo genotoxicity, we treated mice with Allura Red AC and investigated the induction of DNA damage (liver, glandular stomach), clastogenicity/anuegenicity (bone marrow), and mutagenicity (liver, glandular stomach) using Comet assays, micronucleus tests, and transgenic gene mutation assays, respectively. All studies were conducted in accordance with the Organization for Economic Co-operation and Development (OECD) guideline. Although Allura Red AC was administered up to the maximum doses recommended by the OECD guideline, no genotoxic effect was observed in any of the genotoxic endpoints. These data clearly show no evidence of in vivo genotoxic potential of Allura Red AC administered up to the maximum doses in mice.

  18. Phylogenetic Ecology of the Freshwater Actinobacteria acI Lineage▿ †

    PubMed Central

    Newton, Ryan J.; Jones, Stuart E.; Helmus, Matthew R.; McMahon, Katherine D.

    2007-01-01

    The acI lineage of freshwater Actinobacteria is a cosmopolitan and often numerically dominant member of lake bacterial communities. We conducted a survey of acI 16S rRNA genes and 16S-23S rRNA internal transcribed spacer regions from 18 Wisconsin lakes and used standard nonphylogenetic and phylogenetic statistical approaches to investigate the factors that determine acI community composition at the local scale (within lakes) and at the regional scale (across lakes). Phylogenetic reconstruction of 434 acI 16S rRNA genes revealed a well-defined and highly resolved phylogeny. Eleven previously unrecognized monophyletic clades, each with ≥97.9% within-clade 16S rRNA gene sequence identity, were identified. Clade community similarity positively correlated with lake environmental similarity but not with geographic distance, implying that the lakes represent a single biotic region containing environmental filters for communities that have similar compositions. Phylogenetically disparate clades within the acI lineage were most abundant at the regional scale, and local communities were comprised of more closely related clades. Lake pH was a strong predictor of the community composition, but only when lakes with a pH below 6 were included in the data set. In the remaining lakes (pH above 6) biogeographic patterns in the landscape were instead a predictor of the observed acI community structure. The nonrandom distribution of the newly defined acI clades suggests potential ecophysiological differences between the clades, with acI clades AI, BII, and BIII preferring acidic lakes and acI clades AII, AVI, and BI preferring more alkaline lakes. PMID:17827330

  19. Accelerating Spectrum Sharing Technologies

    SciTech Connect

    Juan D. Deaton; Lynda L. Brighton; Rangam Subramanian; Hussein Moradi; Jose Loera

    2013-09-01

    Spectrum sharing potentially holds the promise of solving the emerging spectrum crisis. However, technology innovators face the conundrum of developing spectrum sharing technologies without the ability to experiment and test with real incumbent systems. Interference with operational incumbents can prevent critical services, and the cost of deploying and operating an incumbent system can be prohibitive. Thus, the lack of incumbent systems and frequency authorization for technology incubation and demonstration has stymied spectrum sharing research. To this end, industry, academia, and regulators all require a test facility for validating hypotheses and demonstrating functionality without affecting operational incumbent systems. This article proposes a four-phase program supported by our spectrum accountability architecture. We propose that our comprehensive experimentation and testing approach for technology incubation and demonstration will accelerate the development of spectrum sharing technologies.

  20. The infrared spectrum of KH

    NASA Astrophysics Data System (ADS)

    Haese, Nathan N.; Liu, Di-Jia; Altman, Robert S.

    1984-11-01

    Reported here is the first observation of the infrared spectrum of KH. Fundamental bands and first hotbands of the 39KH and 41KH isotopic forms were measured at high resolution using a diode laser based spectrometer. An ac glow discharge through potassium vapor and hydrogen gas was used to produce KH. A combined isotopic Dunham coefficient analysis was used to fit all the spectra, with the Dunham coefficients for 39KH coming out as Y10=985.6714(30) cm-1, Y20=-14.9013(10) cm-1, Y01=3.416 40(10) cm-1, Y11=-0.085 313(26) cm-1, Y21=5.41(60)×10-4 cm-1, Y02=-1.6354(36)×10-4 cm-1, Y12=1.13(10)×10-6 cm-1, Y03=7.6(8)×10-9 cm-1, (quoted at 2σ error limits). A bond length of 2.241 152(16) Å and a Dunham corrected value for ωe of 986.0505(30) cm-1 are obtained. The pressure broadening of KH by H2 and the chemistry of KH formation in the glow discharge plasma are also discussed.

  1. Three phase AC motor controller

    DOEpatents

    Vuckovich, Michael; Wright, Maynard K.; Burkett, John P.

    1984-03-20

    A motor controller for a three phase AC motor (10) which is adapted to operate bidirectionally from signals received either from a computer (30) or a manual control (32). The controller is comprised of digital logic circuit means which implement a forward and reverse command signal channel (27, 29) for the application of power through the forward and reverse power switching relays (16, 18, 20, 22). The digital logic elements are cross coupled to prevent activation of both channels simultaneously and each includes a plugging circuit (65, 67) for stopping the motor upon the removal of control signal applied to one of the two channels (27, 29) for a direction of rotation desired. Each plugging circuit (65, 67) includes a one-shot pulse signal generator (88, 102) which outputs a single pulse signal of predetermined pulsewidth which is adapted to inhibit further operation of the application of power in the channel which is being activated and to apply a reversal command signal to the other channel which provides a reversed phase application of power to the motor for a period defined by the pulse-width output of the one-shot signal generator to plug the motor (10) which will then be inoperative until another rotational command signal is applied to either of the two channels.

  2. AC impedance spectroscopy studies on solid-state sintered zinc aluminum oxide (ZnAl2O4) ceramics

    NASA Astrophysics Data System (ADS)

    Kumar, B. Rajesh; Rao, T. Subba

    2012-07-01

    In the present investigation Zinc Aluminum Oxide (ZnAl2O4) is prepared by solid-state reaction technique. Dielectric constant (ɛ'), dielectric loss(tan δ), ac conductivityac) as a function of temperature are studied by varying frequencies from 100 Hz to 1MHz using an impedance analyzer. The dielectric constant and dielectric loss increases gradually with an increase of temperature, but it decreases with increase of frequency. The ac conductivityac) also increases with increases of frequency. The transition peaks for ZnAl2O4 are observed at 490°C, 510°C, 520°C for the frequencies 1 KHz, 10 KHz and 100 KHz. No transition peaks are found for the frequency 100 Hz and 1 MHz because of high conductive loss.

  3. Nonlinear alternating current conduction in polycrystalline manganites

    SciTech Connect

    Ghosh, T. N.; Nandi, U. N.; Jana, D.; Dey, K.; Giri, S.

    2014-06-28

    The real part of ac conductance Σ(T, f) of yttrium-doped mixed-valent polycrystalline manganite systems La{sub 1−x−y}Y{sub y}Ca{sub x}MnO{sub 3} with x = 0.33 and 0.05 and y = 0.07 and iron doped LaMn{sub 1−x}Fe{sub x}O{sub 3} with x = 0.15 is measured as a function of frequency f by varying zero-frequency Ohmic conductance Σ{sub 0} by T. The former shows a metal-insulator transition, whereas the latter exhibits insulating character throughout the measured temperature range. At a fixed temperature T, Σ(T, f) remains almost constant to the value Σ{sub 0} up to a certain frequency, known as the onset frequency f{sub c} and increases from Σ{sub 0} as frequency is increased from f{sub c}. Scaled appropriately, the data for Σ(T, f) at different T fall on the same universal curve, indicating the existence of a general scaling formalism for the ac conductance. f{sub c} scales with Σ{sub 0} as f{sub c}∼Σ{sub 0}{sup x{sub f}}, where x{sub f} is the nonlinearity exponent characterising the onset. With the help of data for ac conduction, it is shown that x{sub f} is very much phase sensitive and can be used to characterize the different phases in a manganite system originated due to change in temperature or disorder. Scaling theories and existing theoretical models are used to analyze the results of ac conduction and the nonlinearity exponent x{sub f}.

  4. Memory effect in ac plasma displays

    NASA Astrophysics Data System (ADS)

    Szlenk, K.; Obuchowicz, E.

    1993-10-01

    The bistable or `memory' mode of operation of an ac plasma display panel is presented. The difference between dc and ac plasma panel operation from the point of view of memory function is discussed. The graphic ac plasma display with thin film Cr-Cu-Cr electrodes was developed in OBREP and its basic parameters are described. It consists of 36 X 59 picture elements, its outer dimensions are: 76 X 52 mm2 and the screen size is: 49 X 30 mm2. The different dielectric glass materials were applied as dielectric layers and the influence of the properties of these materials on display parameters and memory function was investigated.

  5. Superconductor coil geometry and ac losses

    NASA Technical Reports Server (NTRS)

    Pierce, T. V., Jr.; Zapata, R. N.

    1976-01-01

    An empirical relation is presented which allows simple computation of volume-averaged winding fields from central fields for coils of small rectangular cross sections. This relation suggests that, in certain applications, ac-loss minimization can be accomplished by use of low winding densities, provided that hysteresis losses are independent of winding density. The ac-loss measurements on coils wound of twisted multifilamentary composite superconductors show no significant dependence on ac losses on winding density, thus permitting the use of winding density as an independent design parameter in loss minimization.

  6. SLAM, a Mathematica interface for SUSY spectrum generators

    NASA Astrophysics Data System (ADS)

    Marquard, Peter; Zerf, Nikolai

    2014-03-01

    We present and publish a Mathematica package, which can be used to automatically obtain any numerical MSSM input parameter from SUSY spectrum generators, which follow the SLHA standard, like SPheno, SOFTSUSY, SuSeFLAV or Suspect. The package enables a very comfortable way of numerical evaluations within the MSSM using Mathematica. It implements easy to use predefined high scale and low scale scenarios like mSUGRA or mhmax and if needed enables the user to directly specify the input required by the spectrum generators. In addition it supports an automatic saving and loading of SUSY spectra to and from a SQL data base, avoiding the rerun of a spectrum generator for a known spectrum. Catalogue identifier: AERX_v1_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AERX_v1_0.html Program obtainable from: CPC Program Library, Queen’s University, Belfast, N. Ireland Licensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.html No. of lines in distributed program, including test data, etc.: 4387 No. of bytes in distributed program, including test data, etc.: 37748 Distribution format: tar.gz Programming language: Mathematica. Computer: Any computer where Mathematica version 6 or higher is running providing bash and sed. Operating system: Linux. Classification: 11.1. External routines: A SUSY spectrum generator such as SPheno, SOFTSUSY, SuSeFLAV or SUSPECT Nature of problem: Interfacing published spectrum generators for automated creation, saving and loading of SUSY particle spectra. Solution method: SLAM automatically writes/reads SLHA spectrum generator input/output and is able to save/load generated data in/from a data base. Restrictions: No general restrictions, specific restrictions are given in the manuscript. Running time: A single spectrum calculation takes much less than one second on a modern PC.

  7. Exenatide: AC 2993, AC002993, AC2993A, exendin 4, LY2148568.

    PubMed

    2004-01-01

    Exenatide [AC002993, AC2993A, AC 2993, LY2148568, exendin 4], a glucagon-like peptide-1 (GLP-1) agonist, is a synthetic exendin 4 compound under development with Amylin Pharmaceuticals for the treatment of type 2 diabetes. Both exendin 4 and its analogue, exendin 3, are 39-amino acid peptides isolated from Heloderma horridum lizard venom that have different amino acids at positions 2 and 3, respectively. Exendins are able to stimulate insulin secretion in response to rising blood glucose levels, and modulate gastric emptying to slow the entry of ingested sugars into the bloodstream. Amylin Pharmaceuticals acquired exclusive patent rights for the two exendin compounds (exendin 3 and exendin 4) from the originator, Dr John Eng (Bronx, NY, US). On 20 September 2002, Amylin and Eli Lilly signed a collaborative agreement for the development and commercialisation of exenatide for type 2 diabetes. Under the terms of the agreement, Eli Lilly has paid Amylin a licensing fee of 80 million US dollars and bought Amylin's stock worth 30 million US dollars at 18.69 US dollars a share. After the initial payment, Eli Lilly will pay Amylin up to 85 US dollars million upon reaching certain milestones and also make an additional payment of up to 130 million US dollars upon global commercialisation of exenatide. Both companies will share the US development and commercialisation costs, while Eli Lilly will pick up up to 80% of development costs and all commercialisation costs outside the US. Amylin and Eli Lilly will equally share profit from sales in the US, while Eli Lilly will get 80% of the profit outside the US and Amylin will get the rest. This agreement has also enabled Amylin to train its sales force to co-promote Lilly's human growth hormone Humatrope. Alkermes will receive research and development funding and milestone payments, and also a combination of royalty payments and manufacturing fees based on product sales. Alkermes undertakes the responsibility for the development

  8. Frequency-dependent conductivity in bismuth-vanadate glassy semiconductors

    NASA Astrophysics Data System (ADS)

    Ghosh, Aswini

    1990-01-01

    The first measurements are reported for the frequency-dependent (ac) conductivity (real as well as imaginary parts) for various compositions of the bismuth-vanadate glassy semiconductors in the frequency range 102-105 Hz and in the temperature range 77-420 K. The behavior of the ac conductivity is broadly similar to what has been observed previously in many other types of amorphous semiconductors, namely, nearly linear frequency dependence and weak temperature dependence. The experimental results are analyzed with reference to various theoretical models based on quantum-mechanical tunneling and classical hopping over barriers. The analysis shows that the temperature dependence of the ac conductivity is consistent with the simple quantum-mechanical tunneling model at low temperatures; however, this model completely fails to predict the observed temperature dependence of the frequency exponent. The overlapping-large-polaron tunneling model can explain the temperature dependence of the frequency exponent at low temperatures. Fitting of this model to the low-temperature data yields a reasonable value of the wave-function decay constant. However, this model predicts the temperature dependence of the ac conductivity much higher than what actual data showed. The correlated barrier hopping model is consistent with the temperature dependence of both the ac conductivity and its frequency exponent. This model provides reasonable values of the maximum barrier heights but higher values of characteristic relaxation times.

  9. Late gadolinium enhanced cardiovascular magnetic resonance of lamin A/C gene mutation related dilated cardiomyopathy

    PubMed Central

    2011-01-01

    Background The purpose of this study was to identify early features of lamin A/C gene mutation related dilated cardiomyopathy (DCM) with cardiovascular magnetic resonance (CMR). We characterise myocardial and functional findings in carriers of lamin A/C mutation to facilitate the recognition of these patients using this method. We also investigated the connection between myocardial fibrosis and conduction abnormalities. Methods Seventeen lamin A/C mutation carriers underwent CMR. Late gadolinium enhancement (LGE) and cine images were performed to evaluate myocardial fibrosis, regional wall motion, longitudinal myocardial function, global function and volumetry of both ventricles. The location, pattern and extent of enhancement in the left ventricle (LV) myocardium were visually estimated. Results Patients had LV myocardial fibrosis in 88% of cases. Segmental wall motion abnormalities correlated strongly with the degree of enhancement. Myocardial enhancement was associated with conduction abnormalities. Sixty-nine percent of our asymptomatic or mildly symptomatic patients showed mild ventricular dilatation, systolic failure or both in global ventricular analysis. Decreased longitudinal systolic LV function was observed in 53% of patients. Conclusions Cardiac conduction abnormalities, mildly dilated LV and depressed systolic dysfunction are common in DCM caused by a lamin A/C gene mutation. However, other cardiac diseases may produce similar symptoms. CMR is an accurate tool to determine the typical cardiac involvement in lamin A/C cardiomyopathy and may help to initiate early treatment in this malignant familiar form of DCM. PMID:21689390

  10. Measurement of AC electrical characteristics of SSC superconducting dipole magnets

    SciTech Connect

    Smedley, K M; Shafer, R E

    1992-01-01

    Experiments were conducted to measure the AC electrical characteristics of SSC superconducting dipole magnets over the frequency range of 0.1 Hz to 10 kHz. A magnet equivalent circuit representing the magnet DC inductance, eddy current losses, coil-to-ground and turn-to-turn capacitance, was synthesized from the experimental data. This magnet equivalent circuit can be used to predict the current ripple distribution along the superconducting magnet string and can provide dynamic information for the design of the collider current regulation loop.

  11. AC electrical properties of FeIn2S4

    NASA Astrophysics Data System (ADS)

    Niftiev, N. N.; Tagiev, O. B.; Muradov, M. B.; Mamedov, F. M.

    2012-04-01

    The frequency and temperature dependences of the ac capacitance and resistivity of FeIn2S4 semiconductors are studied. Resonances are observed at certain temperatures in the frequency range (2.5-5.0) × 105 Hz. The permittivity of the crystals and the activation energy of charge carriers are determined. It is found that electrical conduction in the given temperature interval is governed by an activation mechanism. The activation energy is frequency-dependent, because the relaxation time of barrier layers decreases with rising frequency.

  12. High School Teachers Win ACS Prizes

    NASA Astrophysics Data System (ADS)

    Editorial Staff, Jce

    2009-07-01

    William E. Snyder is the 2009 winner of the ACS Division of Chemical Education Central Region Award for Excellence in High School Teaching; Sally Mitchell is the winner of the 2009 James Bryant Conant Award in High School Chemistry Teaching.

  13. Radiation detector spectrum simulator

    DOEpatents

    Wolf, M.A.; Crowell, J.M.

    1985-04-09

    A small battery operated nuclear spectrum simulator having a noise source generates pulses with a Gaussian distribution of amplitudes. A switched dc bias circuit cooperating therewith to generate several nominal amplitudes of such pulses and a spectral distribution of pulses that closely simulates the spectrum produced by a radiation source such as Americium 241.

  14. Radiation detector spectrum simulator

    DOEpatents

    Wolf, Michael A.; Crowell, John M.

    1987-01-01

    A small battery operated nuclear spectrum simulator having a noise source nerates pulses with a Gaussian distribution of amplitudes. A switched dc bias circuit cooperating therewith generates several nominal amplitudes of such pulses and a spectral distribution of pulses that closely simulates the spectrum produced by a radiation source such as Americium 241.

  15. Fetal Alcohol Spectrum Disorder

    ERIC Educational Resources Information Center

    Caley, Linda M.; Kramer, Charlotte; Robinson, Luther K.

    2005-01-01

    Fetal alcohol spectrum disorder (FASD) is a serious and widespread problem in this country. Positioned within the community with links to children, families, and healthcare systems, school nurses are a critical element in the prevention and treatment of those affected by fetal alcohol spectrum disorder. Although most school nurses are familiar…

  16. The CMBR spectrum

    SciTech Connect

    Stebbins, A.

    1997-05-01

    Here we give an introduction to the observed spectrum of the Cosmic Microwave Background Radiation (CMBR) and discuss what can be learned about it. Particular attention will be given to how Compton scattering can distort the spectrum of the CMBR. An incomplete bibliography of relevant papers is also provided.

  17. Continuous-function ground conductivity model for the determination of electric railway earth conductance

    SciTech Connect

    Carpenter, D.C. ); Hill, R.J. . School of Electronic and Electrical Engineering)

    1993-09-01

    A method is described for the determination of ground conductivity as a continuous function of depth and frequency for applications along spatially linear structures such as railway tracks. The technique involves measurements of mutual resistance using a modified dipole array excited with AC currents up to audio frequency. After representation of the experimental data by analytic functions, the ground conductivity-depth variation is obtained as a degenerate hypergeometric function. The determined ground conductivity is utilized to model the self and mutual conductance of and between the running rails in a single-track railway. The result is verified by experimental measurement.

  18. Three-phase-to-two-phase direct AC-AC converter with three leg structure

    NASA Astrophysics Data System (ADS)

    Kwak, S.-S.

    2014-05-01

    A three-phase-to-two-phase ac-ac converter is, along with a modulation strategy based on the space vector scheme, introduced to directly drive two-phase output ac systems with high input power quality. The converter is capable of synthesising two sinusoidal output voltages with variable output frequency and arbitrary magnitude in quadrature phase-shift as well as sinusoidal input currents.

  19. Phase protection system for ac power lines

    NASA Technical Reports Server (NTRS)

    Wong, W. J. (Inventor)

    1974-01-01

    The system described provides protection for phase sensitive loads from being or remaining connected to ac power lines whenever a phase reversal occurs. It comprises a solid state phase detection circuit, a dc power relay circuit, an ac-to-dc converter for energizing the relay circuit, and a bistable four terminal transducer coupled between the phase detection circuit and the power relay circuit, for controlling both circuits.

  20. Calorimetric method of ac loss measurement in a rotating magnetic field.

    PubMed

    Ghoshal, P K; Coombs, T A; Campbell, A M

    2010-07-01

    A method is described for calorimetric ac-loss measurements of high-T(c) superconductors (HTS) at 80 K. It is based on a technique used at 4.2 K for conventional superconducting wires that allows an easy loss measurement in parallel or perpendicular external field orientation. This paper focuses on ac loss measurement setup and calibration in a rotating magnetic field. This experimental setup is to demonstrate measuring loss using a temperature rise method under the influence of a rotating magnetic field. The slight temperature increase of the sample in an ac-field is used as a measure of losses. The aim is to simulate the loss in rotating machines using HTS. This is a unique technique to measure total ac loss in HTS at power frequencies. The sample is mounted on to a cold finger extended from a liquid nitrogen heat exchanger (HEX). The thermal insulation between the HEX and sample is provided by a material of low thermal conductivity, and low eddy current heating sample holder in vacuum vessel. A temperature sensor and noninductive heater have been incorporated in the sample holder allowing a rapid sample change. The main part of the data is obtained in the calorimetric measurement is used for calibration. The focus is on the accuracy and calibrations required to predict the actual ac losses in HTS. This setup has the advantage of being able to measure the total ac loss under the influence of a continuous moving field as experienced by any rotating machines.

  1. Calorimetric method of ac loss measurement in a rotating magnetic field

    SciTech Connect

    Ghoshal, P. K.; Coombs, T. A.; Campbell, A. M.

    2010-07-15

    A method is described for calorimetric ac-loss measurements of high-T{sub c} superconductors (HTS) at 80 K. It is based on a technique used at 4.2 K for conventional superconducting wires that allows an easy loss measurement in parallel or perpendicular external field orientation. This paper focuses on ac loss measurement setup and calibration in a rotating magnetic field. This experimental setup is to demonstrate measuring loss using a temperature rise method under the influence of a rotating magnetic field. The slight temperature increase of the sample in an ac-field is used as a measure of losses. The aim is to simulate the loss in rotating machines using HTS. This is a unique technique to measure total ac loss in HTS at power frequencies. The sample is mounted on to a cold finger extended from a liquid nitrogen heat exchanger (HEX). The thermal insulation between the HEX and sample is provided by a material of low thermal conductivity, and low eddy current heating sample holder in vacuum vessel. A temperature sensor and noninductive heater have been incorporated in the sample holder allowing a rapid sample change. The main part of the data is obtained in the calorimetric measurement is used for calibration. The focus is on the accuracy and calibrations required to predict the actual ac losses in HTS. This setup has the advantage of being able to measure the total ac loss under the influence of a continuous moving field as experienced by any rotating machines.

  2. Calorimetric method of ac loss measurement in a rotating magnetic field

    NASA Astrophysics Data System (ADS)

    Ghoshal, P. K.; Coombs, T. A.; Campbell, A. M.

    2010-07-01

    A method is described for calorimetric ac-loss measurements of high-Tc superconductors (HTS) at 80 K. It is based on a technique used at 4.2 K for conventional superconducting wires that allows an easy loss measurement in parallel or perpendicular external field orientation. This paper focuses on ac loss measurement setup and calibration in a rotating magnetic field. This experimental setup is to demonstrate measuring loss using a temperature rise method under the influence of a rotating magnetic field. The slight temperature increase of the sample in an ac-field is used as a measure of losses. The aim is to simulate the loss in rotating machines using HTS. This is a unique technique to measure total ac loss in HTS at power frequencies. The sample is mounted on to a cold finger extended from a liquid nitrogen heat exchanger (HEX). The thermal insulation between the HEX and sample is provided by a material of low thermal conductivity, and low eddy current heating sample holder in vacuum vessel. A temperature sensor and noninductive heater have been incorporated in the sample holder allowing a rapid sample change. The main part of the data is obtained in the calorimetric measurement is used for calibration. The focus is on the accuracy and calibrations required to predict the actual ac losses in HTS. This setup has the advantage of being able to measure the total ac loss under the influence of a continuous moving field as experienced by any rotating machines.

  3. Prognostic value of Muc5AC in gastric cancer: A meta-analysis

    PubMed Central

    Zhang, Chuan-Tao; He, Ke-Cheng; Pan, Fei; Li, Yuan; Wu, Jiang

    2015-01-01

    AIM: To assess the correlation between decreased Muc5AC expression and patients’ survival and clinicopathological characteristics by conducting a meta-analysis. METHODS: Literature searches were performed in PubMed and EMBASE, and 11 studies met our criteria. Summary hazard ratios or odds ratios (ORs) with 95% confidence intervals (CIs) were calculated to estimate the effect. For the pooled analysis of the correlation between decreased Muc5AC expression and clinicopathological characteristics (tumour invasion depth, lymph node metastasis, tumour-node-metastasis stage, tumour size, venous invasion and lymphatic invasion), ORs and their variance were combined to estimate the effect. RESULTS: Eleven retrospective cohort studies comprising 2135 patients were included to assess the association between Muc5AC expression and overall survival and/or clinicopathological characteristics. Decreased Muc5AC expression was significantly correlated with poor overall survival of gastric cancer patients (pooled HR = 1.35, 95%CI: 1.08-1.7). Moreover, decreased Muc5AC expression was also significantly associated with tumour invasion depth (pooled OR = 2.12, 95%CI: 1.56-2.87) and lymph node metastasis (pooled OR = 1.56, 95%CI: 1.00-2.44) in gastric cancer. CONCLUSION: Decreased Muc5AC expression might be a poor prognostic predictor for gastric cancer. PMID:26420972

  4. 21 CFR 886.1630 - AC-powered photostimulator.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false AC-powered photostimulator. 886.1630 Section 886...) MEDICAL DEVICES OPHTHALMIC DEVICES Diagnostic Devices § 886.1630 AC-powered photostimulator. (a) Identification. An AC-powered photostimulator is an AC-powered device intended to provide light stimulus...

  5. 21 CFR 886.1630 - AC-powered photostimulator.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 8 2011-04-01 2011-04-01 false AC-powered photostimulator. 886.1630 Section 886...) MEDICAL DEVICES OPHTHALMIC DEVICES Diagnostic Devices § 886.1630 AC-powered photostimulator. (a) Identification. An AC-powered photostimulator is an AC-powered device intended to provide light stimulus...

  6. 21 CFR 886.1850 - AC-powered slitlamp biomicroscope.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false AC-powered slitlamp biomicroscope. 886.1850... (CONTINUED) MEDICAL DEVICES OPHTHALMIC DEVICES Diagnostic Devices § 886.1850 AC-powered slitlamp biomicroscope. (a) Identification. An AC-powered slitlamp biomicroscope is an AC-powered device that is...

  7. 21 CFR 886.1850 - AC-powered slitlamp biomicroscope.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 8 2011-04-01 2011-04-01 false AC-powered slitlamp biomicroscope. 886.1850... (CONTINUED) MEDICAL DEVICES OPHTHALMIC DEVICES Diagnostic Devices § 886.1850 AC-powered slitlamp biomicroscope. (a) Identification. An AC-powered slitlamp biomicroscope is an AC-powered device that is...

  8. 21 CFR 888.1240 - AC-powered dynamometer.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 8 2011-04-01 2011-04-01 false AC-powered dynamometer. 888.1240 Section 888.1240...) MEDICAL DEVICES ORTHOPEDIC DEVICES Diagnostic Devices § 888.1240 AC-powered dynamometer. (a) Identification. An AC-powered dynamometer is an AC-powered device intended for medical purposes to...

  9. 21 CFR 886.4440 - AC-powered magnet.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false AC-powered magnet. 886.4440 Section 886.4440 Food... DEVICES OPHTHALMIC DEVICES Surgical Devices § 886.4440 AC-powered magnet. (a) Identification. An AC-powered magnet is an AC-powered device that generates a magnetic field intended to find and...

  10. 21 CFR 886.4440 - AC-powered magnet.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 8 2014-04-01 2014-04-01 false AC-powered magnet. 886.4440 Section 886.4440 Food... DEVICES OPHTHALMIC DEVICES Surgical Devices § 886.4440 AC-powered magnet. (a) Identification. An AC-powered magnet is an AC-powered device that generates a magnetic field intended to find and...

  11. 21 CFR 886.4440 - AC-powered magnet.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 8 2013-04-01 2013-04-01 false AC-powered magnet. 886.4440 Section 886.4440 Food... DEVICES OPHTHALMIC DEVICES Surgical Devices § 886.4440 AC-powered magnet. (a) Identification. An AC-powered magnet is an AC-powered device that generates a magnetic field intended to find and...

  12. 21 CFR 886.4440 - AC-powered magnet.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 8 2012-04-01 2012-04-01 false AC-powered magnet. 886.4440 Section 886.4440 Food... DEVICES OPHTHALMIC DEVICES Surgical Devices § 886.4440 AC-powered magnet. (a) Identification. An AC-powered magnet is an AC-powered device that generates a magnetic field intended to find and...

  13. 21 CFR 886.4440 - AC-powered magnet.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 8 2011-04-01 2011-04-01 false AC-powered magnet. 886.4440 Section 886.4440 Food... DEVICES OPHTHALMIC DEVICES Surgical Devices § 886.4440 AC-powered magnet. (a) Identification. An AC-powered magnet is an AC-powered device that generates a magnetic field intended to find and...

  14. 21 CFR 888.1240 - AC-powered dynamometer.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false AC-powered dynamometer. 888.1240 Section 888.1240...) MEDICAL DEVICES ORTHOPEDIC DEVICES Diagnostic Devices § 888.1240 AC-powered dynamometer. (a) Identification. An AC-powered dynamometer is an AC-powered device intended for medical purposes to...

  15. Electrical conduction through DNA molecule.

    PubMed

    Abdalla, S

    2011-09-01

    Several disorder parameters, inside the DNA molecule, lead to localization of charge carriers inside potential wells in the lowest unoccupied and highest occupied molecular orbits (LUMO and HOMO) which affects drastically the electrical conduction through the molecule, and demonstrates that the band carriers play an essential role in the conduction mechanism. So, a model is presented to shed light on the role of electrons of the LUMO in the electrical conduction through the DNA molecule. DC-, AC-conductivity and dielectric permittivity experimental data are well fitted with the presented model giving evidence that the free carriers in the LUMO and HOMO are responsible to make the DNA molecule conductor, insulator or semiconductor. The obtained results show that the localized charge carriers in the DNA molecule are characterized by four different types of relaxation phenomena which are thermally activated by corresponding four activation energies at 0.56 eV, 0.33 eV, 0.24 eV, and 0.05 eV respectively. Moreover, the calculations after the model, at room temperature, show that the time of the relaxation times of the current carriers are in the order of 5 × 10(-2)s, 1.74 × 10(-4)s, 5 × 10(-7)s, and 1.6 × 10(-10)s, respectively.

  16. Instantaneous velocity measurement of AC electroosmotic flows by laser induced fluorescence photobleaching anemometer with high temporal resolution

    NASA Astrophysics Data System (ADS)

    Zhao, Wei; Yang, Fang; Qiao, Rui; Wang, Guiren; Rui Qiao Collaboration

    2015-11-01

    Understanding the instantaneous response of flows to applied AC electric fields may help understand some unsolved issues in induced-charge electrokinetics and enhance performance of microfluidic devices. Since currently available velocimeters have difficulty in measuring velocity fluctuations with frequency higher than 1 kHz, most experimental studies so far focus only on the average velocity measurement in AC electrokinetic flows. Here, we present measurements of AC electroosmotic flow (AC-EOF) response time in microchannels by a novel velocimeter with submicrometer spatial resolution and microsecond temporal resolution, i.e. laser-induced fluorescence photobleaching anemometer (LIFPA). Several parameters affecting the AC-EOF response time to the applied electric signal were investigated, i.e. channel length, transverse position and solution conductivity. The experimental results show that the EOF response time under a pulsed electric field decreases with the reduction of the microchannel length, distance between the detection position to the wall and the conductivity of the solution. This work could provide a new powerful tool to measure AC electrokinetics and enhance our understanding of AC electrokinetic flows.

  17. Growth of 4″ diameter polycrystalline diamond wafers with high thermal conductivity by 915 MHz microwave plasma chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    A, F. POPOVICH; V, G. RALCHENKO; V, K. BALLA; A, K. MALLIK; A, A. KHOMICH; A, P. BOLSHAKOV; D, N. SOVYK; E, E. ASHKINAZI; V, Yu YUROV

    2017-03-01

    Polycrystalline diamond (PCD) films 100 mm in diameter are grown by 915 MHz microwave plasma chemical vapor deposition (MPCVD) at different process parameters, and their thermal conductivity (TC) is evaluated by a laser flash technique (LFT) in the temperature range of 230–380 K. The phase purity and quality of the films are assessed by micro-Raman spectroscopy based on the diamond Raman peak width and the amorphous carbon (a-C) presence in the spectra. Decreasing and increasing dependencies for TC with temperature are found for high and low quality samples, respectively. TC, as high as 1950 ± 230 W m‑1 K‑1 at room temperature, is measured for the most perfect material. A linear correlation between the TC at room temperature and the fraction of the diamond component in the Raman spectrum for the films is established.

  18. 78 FR 49318 - Availability of Draft Advisory Circular (AC) 90-106A and AC 20-167A

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-08-13

    ... Federal Aviation Administration Availability of Draft Advisory Circular (AC) 90-106A and AC 20- 167A...: This notice announces the availability of draft Advisory Circular (AC) 90-106A, Enhanced Flight Vision Systems and draft AC 20- 167A, Airworthiness Approval of Enhanced Vision System, Synthetic Vision...

  19. Single grain boundary characterization of Nb-doped SrTiO{sub 3} bicrystals using ac four-point impedance spectroscopy

    SciTech Connect

    Hwang, Jin-Ha; Johnson, Kevin D.; Mason, Thomas O.; Dravid, Vinayak P.

    2000-05-01

    AC four-point impedance spectroscopy has been applied to Nb-doped SrTiO{sub 3} bicrystals. Due to the simplified geometry and highly conductive bulk of the bicrystal, the reference impedance of the electrode was significantly reduced, validating the applicability of ac four-point impedance spectroscopy for electroceramics. DC current-voltage characteristics without any interference due to electrodes confirmed these ac measurements. Using ac four-point impedance spectroscopy, grain boundary contributions are isolated and the corresponding grain boundary thickness and resistivity are estimated. (c) 2000 American Institute of Physics.

  20. Cyclic stress-strain curve determination for D6AC steel by three methods

    NASA Technical Reports Server (NTRS)

    Nachtigall, A. J.

    1977-01-01

    The room temperature cyclic stress-strain was determined for D6AC low alloy steel by three different methods. The method that involves the use of a single specimen monotonic tension test after cyclic straining provided the best agreement with the accepted basic method which requires a number of companion specimen tests. The single specimen test is also the simplest to conduct.

  1. Heat conduction in conducting polyaniline nanofibers

    NASA Astrophysics Data System (ADS)

    Nath, Chandrani; Kumar, A.; Syu, K.-Z.; Kuo, Y.-K.

    2013-09-01

    Thermal conductivity and specific heat of conducting polyaniline nanofibers are measured to identify the nature of heat carrying modes combined with their inhomogeneous structure. The low temperature thermal conductivity results reveal crystalline nature while the high temperature data confirm the amorphous nature of the material suggesting heterogeneous model for conducting polyaniline. Extended acoustic phonons dominate the low temperature (<100 K) heat conduction, while localized optical phonons hopping, assisted by the extended acoustic modes, account for the high temperature (>100 K) heat conduction.

  2. IRIS Spectrum Line Plot

    NASA Video Gallery

    This video shows a line plot of the spectrum. The spectra here are shown for various locations on the Sun. The changes in the movie are caused by differing physical conditions in the locations. Cre...

  3. Quantum Spread Spectrum Communication

    SciTech Connect

    Humble, Travis S

    2010-01-01

    We demonstrate that spectral teleportation can coherently dilate the spectral probability amplitude of a single photon. In preserving the encoded quantum information, this variant of teleportation subsequently enables a form of quantum spread spectrum communication.

  4. Autism Spectrum Disorder (ASD)

    MedlinePlus

    ... essential data on ASD, search for factors that put children at risk for ASD and possible causes, ... United States to help identify factors that may put children at risk for autism spectrum disorder (ASD) ...

  5. Autism Spectrum Disorder (ASD)

    MedlinePlus

    ... NICHD Research Information Clinical Trials Resources and Publications Autism Spectrum Disorder (ASD): Condition Information Skip sharing on ... Restricted interests and repetitive behaviors Different people with autism can have different symptoms. For this reason, autism ...

  6. Direct effects of 9-anthracene compounds on cystic fibrosis transmembrane conductance regulator gating

    PubMed Central

    Ai, T.; Bompadre, S. G.; Sohma, Y.; Wang, X.; Li, M.; Sohma, Y.; Ai, T.

    2005-01-01

    Anthracene-9-carboxylic acid (9-AC) has been reported to show both potentiation and inhibitory effects on guinea-pig cardiac cAMP-activated chloride channels via two different binding sites, and inhibition of Mg2+-sensitive protein phosphatases has been proposed for the mechanism of 9-AC potentiation effect. In this study, we examined the effects of 9-AC on wild-type and mutant human cystic fibrosis transmembrane conductance regulator (CFTR) chloride channels expressed in NIH3T3 or CHO cells. 9-AC inhibits whole-cell CFTR current in a voltage-dependent manner, whereas the potentiation effect is not affected by membrane potentials. Anthracene-9-methanol, an electro-neutral 9-AC analog, fails to block CFTR, but shows a nearly identical potentiation effect, corroborating the idea that two chemically distinct sites are responsible, respectively, for potentiation and inhibitory actions of 9-AC. 9-AC also enhances the activity of ΔR-CFTR, a constitutively active CFTR mutant whose R-domain is removed. In excised inside-out patches, 9-AC increases Po by prolonging the mean burst durations and shortening the interburst durations. We therefore conclude that two different 9-AC binding sites for potentiation and inhibitory effects on CFTR channels are located outside of the R-domain. We also speculate that 9-AC potentiates CFTR activity by directly affecting CFTR gating. PMID:15290302

  7. Design and synthesis of 225Ac radioimmunopharmaceuticals.

    PubMed

    McDevitt, Michael R; Ma, Dangshe; Simon, Jim; Frank, R Keith; Scheinberg, David A

    2002-12-01

    The alpha-particle-emitting radionuclides 213Bi, 211At, 224Ra are under investigation for the treatment of leukemias, gliomas, and ankylosing spondylitis, respectively. 213Bi and 211At were attached to monoclonal antibodies and used as targeted immunotherapeutic agents while unconjugated 224Ra chloride selectively seeks bone. 225Ac possesses favorable physical properties for radioimmunotherapy (10d half-life and 4 net alpha particles), but has a history of unfavorable radiolabeling chemistry and poor metal-chelate stability. We selected functionalized derivatives of DOTA as the most promising to pursue from out of a group of potential 225Ac chelate compounds. A two-step synthetic process employing either MeO-DOTA-NCS or 2B-DOTA-NCS as the chelating moiety was developed to attach 225Ac to monoclonal antibodies. This method was tested using several different IgG systems. The chelation reaction yield in the first step was 93+/-8% radiochemically pure (n=26). The second step yielded 225Ac-DOTA-IgG constructs that were 95+/-5% radiochemically pure (n=27) and the mean percent immunoreactivity ranged from 25% to 81%, depending on the antibody used. This process has yielded several potential novel targeted 225Ac-labeled immunotherapeutic agents that may now be evaluated in appropriate model systems and ultimately in humans.

  8. From Beamline to Scanner with 225Ac

    NASA Astrophysics Data System (ADS)

    Robertson, Andrew K. H.; Ramogida, Caterina F.; Kunz, Peter; Rodriguez-Rodriguez, Cristina; Schaffer, Paul; Sossi, Vesna

    2016-09-01

    Due to the high linear energy transfer and short range of alpha-radiation, targeted radiation therapy using alpha-emitting pharmaceuticals that successfully target small disease clusters will kill target cells with limited harm to healthy tissue, potentially treating the most aggressive forms of cancer. As the parent of a decay chain with four alpha- and two beta-decays, 225Ac is a promising candidate for such a treatment. However, this requires retention of the entire decay chain at the target site, preventing the creation of freely circulating alpha-emitters that reduce therapeutic effect and increase toxicity to non-target tissues. Two major challenges to 225Ac pharmaceutical development exist: insufficient global supply, and the difficulty of preventing toxicity by retaining the entire decay chain at the target site. While TRIUMF works towards large-scale (C i amounts) production of 225Ac, we already use our Isotope Separation On-Line facility to provide small (< 1 mCi) quantities for in-house chemistry and imaging research that aims to improve and assess 225Ac radiopharmaceutical targeting. This presentation provides an overview of this research program and the journey of 225Ac from the beamline to the scanner. This research is funded by the Natural Sciences and Engineering Research Council of Canada.

  9. Kondo physics in the single-electron transistor with ac driving

    NASA Astrophysics Data System (ADS)

    Nordlander, Peter; Wingreen, Ned S.; Meir, Yigal; Langreth, David C.

    2000-01-01

    Using a time-dependent Anderson Hamiltonian, a quantum dot with an ac voltage applied to a nearby gate is investigated. A rich dependence of the linear response conductance on the external frequency and driving amplitude is demonstrated. At low frequencies a sufficiently strong ac potential produces sidebands of the Kondo peak in the spectral density of the dot, and a slow, roughly logarithmic decrease in conductance over several decades of frequency. At intermediate frequencies, the conductance of the dot displays an oscillatory behavior due to the appearance of Kondo resonances of the satellites of the dot level. At high frequencies, the conductance of the dot can vary rapidly due to the interplay between photon-assisted tunneling and the Kondo resonance.

  10. Participation in Daily Activities of Young Adults with High Functioning Autism Spectrum Disorder

    ERIC Educational Resources Information Center

    McCollum, Mary; LaVesser, Patti; Berg, Christine

    2016-01-01

    Young adults with an autism spectrum disorder (ASD) struggle to assume adult roles. This research assessed the feasibility of using the Adolescent and Young Adult Activity Card Sort (AYA-ACS) with emerging adults with high functioning ASD. Two phases were utilized during this research: (1) comparing the activity participation reported by emerging…

  11. Absolutely continuous spectrum implies ballistic transport for quantum particles in a random potential on tree graphs

    NASA Astrophysics Data System (ADS)

    Aizenman, Michael; Warzel, Simone

    2012-09-01

    We discuss the dynamical implications of the recent proof that for a quantum particle in a random potential on a regular tree graph absolutely continuous (ac) spectrum occurs non-perturbatively through rare fluctuation-enabled resonances. The main result is spelled in the title.

  12. Absolutely continuous spectrum implies ballistic transport for quantum particles in a random potential on tree graphs

    SciTech Connect

    Aizenman, Michael; Warzel, Simone

    2012-09-15

    We discuss the dynamical implications of the recent proof that for a quantum particle in a random potential on a regular tree graph absolutely continuous (ac) spectrum occurs non-perturbatively through rare fluctuation-enabled resonances. The main result is spelled in the title.

  13. Electrical conductivity and modulus formulation in zinc modified bismuth boro-tellurite glasses

    NASA Astrophysics Data System (ADS)

    Dhankhar, Sunil; Kundu, R. S.; Dult, Meenakshi; Murugavel, S.; Punia, R.; Kishore, N.

    2016-09-01

    The ac conductivity of zinc modified tellurium based quaternary glasses having composition 60 TeO2-10 B2O3-(30 - x) Bi2O3-x ZnO; x = 10, 15, 20, 25 and 30 has been investigated in the frequency range 10-1-105 Hz and in temperature range 483-593 K. Frequency and temperature dependent ac conductivity found to obey Jonscher power law modified by Almond-West. DC conductivity, crossover frequency and frequency exponent have been estimated from the fitting of the experimental data of conductivity with Jonscher power law modified by Almond-West. The ac conductivity and its frequency exponent have been analyzed by various theoretical models. In presently studied glasses ac conduction takes place via tunneling of overlapping large polaron tunneling. Activation energy is found to be increased with increase in zinc content and dc conduction takes place via variable range hopping proposed by Mott with some modification suggested by Punia et al. The value of the stretched exponent ( β) obtained by fitting of M^' ' }} reveals the presence of non-Debye type relaxation. Scaling spectra of ac conductivity and electric modulus collapse into a single master curve for all compositions and temperatures, reveals the presence of composition and temperature independent conduction and relaxation process in these glasses. Activation energy of conduction ( W) and electric modulus ( E R ) are nearly equal, indicating that polaron have to overcome the same energy barrier during conduction as well as relaxation processes.

  14. The Effects of the Toxic Cyanobacterium Limnothrix (Strain AC0243) on Bufo marinus Larvae

    PubMed Central

    Daniels, Olivia; Fabbro, Larelle; Makiela, Sandrine

    2014-01-01

    Limnothrix (strain AC0243) is a cyanobacterium, which has only recently been identified as toxin producing. Under laboratory conditions, Bufo marinus larvae were exposed to 100,000 cells mL−1 of Limnothrix (strain AC0243) live cultures for seven days. Histological examinations were conducted post mortem and revealed damage to the notochord, eyes, brain, liver, kidney, pancreas, gastrointestinal tract, and heart. The histopathological results highlight the toxicological impact of this strain, particularly during developmental stages. Toxicological similarities to β-N-Methylamino-l-alanine are discussed. PMID:24662524

  15. Microwave conductance of ferroelectric domain walls in lead titanate

    NASA Astrophysics Data System (ADS)

    Tselev, Alexander; Cao, Ye; Yu, Pu; Kalinin, Sergei V.; Maksymovych, Petro

    Numerous theoretical works predicted electronically conducting domain walls in otherwise insulating ferroelectric crystals. A number of recent experiments reported conducting walls, although conductivity itself and a conclusive proof of conductance mechanism remain elusive, largely due to the electrical contact problem. The latter can be overcome using high-frequency AC voltage. Here we will present our successful measurements of microwave conductance at 180o domain walls in lead titanate using microwave microscopy. AC conducting domain walls can be repeatably reconfigured and have extraordinary stability in time and temperature. AC conductivity is detected even when DC is not. Quantitative modeling reveals that the conductance of domain walls is comparable to doped silicon. We will also present a new and robust mechanism to create charged domain walls in any ferroelectric lattice. Overall, this sets the stage for a new generation of local experiments on conducting domain walls, and furthers the prospects of their application in fast electronic devices. AT, YC, SVK, PM supported by Division of Materials Sciences and Engineering, Office of Science, Basic Energy Sciences, U. S. DOE. PY supported by the National Basic Research Program of China (2015CB921700).

  16. Cultural Basis of Social "Deficits" in Autism Spectrum Disorders

    ERIC Educational Resources Information Center

    Perepa, Prithvi

    2014-01-01

    There is very little research that specifically looks at how autism spectrum disorders are perceived in various communities. This qualitative research was conducted with parents who had children on the autistic spectrum belonging to four different ethnic communities (White British, Somali, West African and South Asian--63 in total) and living in…

  17. Micro acoustic spectrum analyzer

    DOEpatents

    Schubert, W. Kent; Butler, Michael A.; Adkins, Douglas R.; Anderson, Larry F.

    2004-11-23

    A micro acoustic spectrum analyzer for determining the frequency components of a fluctuating sound signal comprises a microphone to pick up the fluctuating sound signal and produce an alternating current electrical signal; at least one microfabricated resonator, each resonator having a different resonant frequency, that vibrate in response to the alternating current electrical signal; and at least one detector to detect the vibration of the microfabricated resonators. The micro acoustic spectrum analyzer can further comprise a mixer to mix a reference signal with the alternating current electrical signal from the microphone to shift the frequency spectrum to a frequency range that is a better matched to the resonant frequencies of the microfabricated resonators. The micro acoustic spectrum analyzer can be designed specifically for portability, size, cost, accuracy, speed, power requirements, and use in a harsh environment. The micro acoustic spectrum analyzer is particularly suited for applications where size, accessibility, and power requirements are limited, such as the monitoring of industrial equipment and processes, detection of security intrusions, or evaluation of military threats.

  18. Optical Properties of AC60 Materials

    NASA Astrophysics Data System (ADS)

    Martin, Michael C.

    1996-03-01

    The alkali intercalated fullerene system A_1C_60 (A=K, Rb, or Cs) undergoes a number of structural and electronic phase transitions. At elevated temperatures the structure is fcc, but when cooled below ~ 100 ^circC the structure becomes dependent on the sample's thermal treatment. Infrared and Raman spectroscopic investigations into the various resultant phases will be presented.^1,2 Upon slow cooling, the C_60 molecules form linear conducting polymers^3 which break the icosahedral symmetry of the pure fullerene and thus activate many previously silent vibrational modes. This phase is unexpectedly found to be stable in air.^4 At much lower temperatures (30-60K) a magnetic transition has been observed; we will present IR data obtained in this thermal region showing indications of a gap-like feature. If the samples are cooled very rapidly from high temperatures, an insulating phase is formed where even more symmetry breaking occurs. We argue that a dimerization of C_60, Rb_2(C_60)_2, is the likely structure in accord with the vibrational spectra,^2 and recent x-ray results. Both lower-symmetry phases of AC_60 can also be used to help identify the IR- and Raman-silent modes of unperturbed C_60. Work done at the State University of New York at Stony Brook in collaboration with Daniel Koller, Peter W. Stephens, Laszlo Mihaly (State University of New York at Stony Brook), C. Kendziora and A. Rosenberg (Naval Research Laboratory). Supported by NSF Grant DMR9202528. ^1Michael C. Martin, Daniel Koller, Xiaoqun Du, Peter W. Stephens and Laszlo Mihaly, Phys. Rev. B 49, 10 818 (1994). ^2Michael C. Martin, Daniel Koller, A. Rosenberg, C. Kendziora, and L. Mihaly, Phys. Rev. B 51, 3210 (1995). ^3P.W. Stephens, G. Bortel, G. Faigel, M. Tegze, A. Jánossy, S. Pekker, G. Oszlányi and L. Forro, Nature (London) 370, 636 (1994). ^4Daniel Koller, Michael C. Martin, Peter W. Stephens, Laszlo Mihaly, Sandor Pekker, Andras Jánossy, Olivier Chauvet and Laszlo Forro, Appl. Phys. Lett. 66

  19. Identifying, Quantifying, and Operationalizing Queer-Spectrum and Trans-Spectrum Students: Assessment and Research in Student Affairs

    ERIC Educational Resources Information Center

    Rankin, Susan; Garvey, Jason C.

    2015-01-01

    This chapter offers both challenges and new directions in conducting quantitative assessments and research with queer-spectrum and trans-spectrum college student populations. Both the challenges and future directions are grounded in the literature and the experiences of the authors.

  20. AC losses of single-core MgB2 wires with different metallic sheaths

    NASA Astrophysics Data System (ADS)

    Kováč, J.; Šouc, J.; Kováč, P.; Hušek, I.

    2015-12-01

    AC losses of single-core MgB2 superconductors with different metallic sheaths (Cu, GlidCop, stainless steel and Monel) have been measured and analyzed. These wires were exposed to external magnetic field with frequencies 72 and 144 Hz and amplitudes up to 0.1 T at temperatures ranged from 18 to 40 K. The obtained results have shown that applied metallic sheath can affect the measured AC loss considerably. In the case of GlidCop and Stainless Steel a negligible small effect of metallic sheath was observed. Strong contribution of eddy currents has been found in the wire with well conductive copper sheath. In the case of Monel sheath, the hysteresis loss of magnetic sheath is dominated and AC loss of MgB2 core is practically not visible.

  1. Broad spectrum solar cell

    DOEpatents

    Walukiewicz, Wladyslaw; Yu, Kin Man; Wu, Junqiao; Schaff, William J.

    2007-05-15

    An alloy having a large band gap range is used in a multijunction solar cell to enhance utilization of the solar energy spectrum. In one embodiment, the alloy is In.sub.1-xGa.sub.xN having an energy bandgap range of approximately 0.7 eV to 3.4 eV, providing a good match to the solar energy spectrum. Multiple junctions having different bandgaps are stacked to form a solar cell. Each junction may have different bandgaps (realized by varying the alloy composition), and therefore be responsive to different parts of the spectrum. The junctions are stacked in such a manner that some bands of light pass through upper junctions to lower junctions that are responsive to such bands.

  2. An unusual meteor spectrum

    NASA Technical Reports Server (NTRS)

    Cook, A. F.; Hemenway, C. L.; Millman, P. M.; Swider, A.

    1973-01-01

    An extraordinary spectrum of a meteor at a velocity of about 18.5 + or - 1.0 km/s was observed with an image orthicon camera. The radiant of the meteor was at an altitude of about 49 deg. It was first seen showing a yellow red continuous spectrum alone at a height of 137 + or - 8 km which is ascribed to the first positive group of nitrogen bands. After the meteor had descended to 116 + or - 6 km above sea level it brightened rapidly from its previous threshold brightness into a uniform continuum, the D-line of neutral sodium appeared, and at height 105 + or - 5 km all the other lines of the spectrum also appeared. The continuum remained dominant to the end. Water of hydration and entrained carbon flakes of characteristic dimension about 0.2 micron or less are proposed as constituents of the meteoroid to explain these phenomena.

  3. Transport AC losses of Ag-sheathed Bi-2223 tapes with different twist-pitch using electrical methods

    NASA Astrophysics Data System (ADS)

    Jang, M.-H.; Wong-Ng, W.

    2006-01-01

    A series of Bi-2223 ([Bi, Pb]:Sr:Ca:Cu:O = 2:2:2:3) tapes with 37 superconducting core filaments was investigated in an attempt to correlate critical current and alternating current (AC) losses with twist-pitch. The twist-pitch of these multi-filamentary tapes which were produced by the powder-in-(Ag)tube (PIT) method varies from 8, 10, 13, 30, 50, 70 mm to ∞ mm (non-twist). Critical current (Ic) measurements which were conducted in zero field by a four-probe method under liquid-nitrogen temperature showed that Ic is greater in the non-twist filament than that in twisted filaments. Among these tapes, three (twist-pitch of 10, 13, and 70 mm) were selected for AC loss experiments under a time-varying transport current. The results of AC loss measurements in general agree with that of the AC loss simulation using the ellipse model of the Norris equation. Simulation results show that the hysteretic AC loss is lowest in the non-twist tape and increases as the twist-pitch decreases. A much greater loss was found in tapes with small twist-pitch, i.e. 10 and 8 mm. Among different possible loss contributions to the total AC losses, the hysteretic loss was determined to be the main source. In addition, microstructural damage of tapes with small twist-pitch appears to contribute to the overall AC losses as well.

  4. NREL Spectrum of Innovation

    ScienceCinema

    None

    2016-07-12

    There are many voices calling for a future of abundant clean energy. The choices are difficult and the challenges daunting. How will we get there? The National Renewable Energy Laboratory integrates the entire spectrum of innovation including fundamental science, market relevant research, systems integration, testing and validation, commercialization and deployment. The innovation process at NREL is interdependent and iterative. Many scientific breakthroughs begin in our own laboratories, but new ideas and technologies come to NREL at any point along the innovation spectrum to be validated and refined for commercial use.

  5. Spectrum of wormholes

    SciTech Connect

    Hawking, S.W. Department of Applied Mathematics and Theoretical Physics, University of Cambridge, Silver Street, Cambridge CB3 9EW ); Page, D.N. Department of Physics, Pennsylvania State University, University Park, PA Theoretical Physics Institute, Department of Physics, University of Alberta, Edmonton, AB )

    1990-10-15

    Wormholes have been studied mainly in the semiclassical approximation as solutions of the classical Euclidean field equations. However, such solutions are rather special, and exist only for certain kinds of matter. On the other hand, one can represent wormholes in a more general manner as solutions of the Wheeler-DeWitt equation with appropriate boundary conditions. Minisuperspace models with massless minimal or conformal scalar fields have a discrete spectrum of these solutions. The Giddings-Strominger instanton solution corresponds to a sum of an infinite number of these solutions. Minisuperspace models with a massive scalar field also appear to have a discrete spectrum of such solutions, whose asymptotic form is given.

  6. Improving VHF Spectrum Utilization

    NASA Technical Reports Server (NTRS)

    Andro, Monty; Orr, Richard; Foore, Larry; Sheehe, Charles; Freeman, Mark; Nguyen, Thanh; Bretmersky, Steven; Laberge, Chuck; Buchanan, David

    2004-01-01

    Limited VHF communications system capacity and increasing air traffic results in congestion of the aviation VHF spectrum. The voice communications errors and delayed channel access create system congestion and air traffic delays. Regulatory subdivision of bands for specific functions limits flexibility in the frequency usage. The objective of this viewgraph presentation is to identify near/mid/far term technologies to improve the performance and spectrum efficiency of current and emerging VHF communications systems. Select technologies with the highest potential, perform research and development to bring them to implementation stage.

  7. NREL Spectrum of Innovation

    SciTech Connect

    2011-01-01

    There are many voices calling for a future of abundant clean energy. The choices are difficult and the challenges daunting. How will we get there? The National Renewable Energy Laboratory integrates the entire spectrum of innovation including fundamental science, market relevant research, systems integration, testing and validation, commercialization and deployment. The innovation process at NREL is interdependent and iterative. Many scientific breakthroughs begin in our own laboratories, but new ideas and technologies come to NREL at any point along the innovation spectrum to be validated and refined for commercial use.

  8. Flat-spectrum speech.

    PubMed

    Schroeder, M R; Strube, H W

    1986-05-01

    Flat-spectrum stimuli, consisting of many equal-amplitude harmonics, produce timbre sensations that can depend strongly on the phase angles of the individual harmonics. For fundamental frequencies in the human pitch range, many realizable timbres have vowel-like perceptual qualities. This observation suggests the possibility of constructing intelligible voiced speech signals that have flat-amplitude spectra. This paper describes a successful experiment of creating several different diphthongs by judicious choice of the phase angles of a flat-spectrum waveform. A possible explanation of the observed vowel timbres lies in the dependence of the short-time amplitude spectra on phase changes.

  9. Range Detection of the Extremely Low-Frequency Magnetic Field Produced by Laptop's AC Adapter

    NASA Astrophysics Data System (ADS)

    Brodić, Darko; Amelio, Alessia

    2017-02-01

    Human exposure to extremely low frequency magnetic field represents a risk to their health. This paper takes into consideration the level of an extremely low-frequency magnetic field between 30 and 300 Hz emitted by an AC laptop adapter. The experiment consists of testing 17 different AC adapters for laptops. During the testing, laptops are operated in a normal operating conditions as well as under heavy load. The magnetic field measurement is conducted in the area around the AC adapter. Obtained data is evaluated according to the critical level of the magnetic field proposed by safety standards. Furthermore, data is classified by a K-medians method in order to determine the critical levels of the magnetic field exposure in the nearby area of the AC adapter. Obtained classifications are evaluated according to safety standards, giving a critical analysis of magnetic field areas at risk. Due to emission of a very strong magnetic field in certain areas, a recommendation for safety use of the AC adapter is proposed.

  10. AC Losses of Prototype HTS Transmission Cables

    SciTech Connect

    Demko, J.A.; Dresner, L.; Hughey, R.L.; Lue, J.W.; Olsen, S.K.; Sinha, U.; Tolbert, J.C.

    1998-09-13

    Since 1995 Southwire Company and Oak Ridge National Laboratory (ORNL) have jointly designed, built, and tested nine, l-m long, high temperature superconducting (HTS) transmission cable prototypes. This paper summarizes the AC loss measurements of five of the cables not reported elsewhere, and compares the losses with each other and with theory developed by Dresner. Losses were measured with both a calorimetric and an electrical technique. Because of the broad resistive transition of the HTS tapes, the cables can be operated stably beyond their critical currents. The AC losses were measured in this region as well as below critical currents. Dresner's theory takes into account the broad resistive transition of the HTS tapes and calculates the AC losses both below and above the critical current. The two sets of AC 10SS data agree with each other and with the theory quite welL In particular, at low currents of incomplete penetration, the loss data agree with the theoretical prediction of hysteresis loss based on only the outer two Iayers carrying the total current.

  11. AC power generation from microbial fuel cells

    NASA Astrophysics Data System (ADS)

    Lobo, Fernanda Leite; Wang, Heming; Forrestal, Casey; Ren, Zhiyong Jason

    2015-11-01

    Microbial fuel cells (MFCs) directly convert biodegradable substrates to electricity and carry good potential for energy-positive wastewater treatment. However, the low and direct current (DC) output from MFC is not usable for general electronics except small sensors, yet commercial DC-AC converters or inverters used in solar systems cannot be directly applied to MFCs. This study presents a new DC-AC converter system for MFCs that can generate alternating voltage in any desired frequency. Results show that AC power can be easily achieved in three different frequencies tested (1, 10, 60 Hz), and no energy storage layer such as capacitors was needed. The DC-AC converter efficiency was higher than 95% when powered by either individual MFCs or simple MFC stacks. Total harmonic distortion (THD) was used to investigate the quality of the energy, and it showed that the energy could be directly usable for linear electronic loads. This study shows that through electrical conversion MFCs can be potentially used in household electronics for decentralized off-grid communities.

  12. Organic magnetoresistance under resonant ac drive

    NASA Astrophysics Data System (ADS)

    Roundy, R. C.; Raikh, M. E.

    2013-09-01

    Motivated by a recent experiment, we develop a theory of organic magnetoresistance (OMAR) in the presence of a resonant ac drive. To this end, we perform a thorough analysis of the dynamics of ac-driven electron-hole polaron pair in magnetic field, which is a sum of external and random hyperfine fields. Resonant ac drive affects the OMAR by modifying the singlet content of the eigenmodes. This, in turn, leads to the change of recombination rate, and ultimately, to the change of the spin-blocking that controls the current. Our analysis demonstrates that, upon increasing the drive amplitude, the blocking eigenmodes of the triplet type acquire a singlet admixture and become unblocking. Most surprisingly, the opposite process goes in parallel: new blocking modes emerge from nonblocking precursors as the drive increases. These emergent blocking modes are similar to subradiant modes in the Dicke effect. A nontrivial evolution of eigenmodes translates into a nontrivial behavior of OMAR with the amplitude of the ac drive: it is initially linear, then passes through a maximum, drops, and finally saturates.

  13. A dry-cooled AC quantum voltmeter

    NASA Astrophysics Data System (ADS)

    Schubert, M.; Starkloff, M.; Peiselt, K.; Anders, S.; Knipper, R.; Lee, J.; Behr, R.; Palafox, L.; Böck, A. C.; Schaidhammer, L.; Fleischmann, P. M.; Meyer, H.-G.

    2016-10-01

    The paper describes a dry-cooled AC quantum voltmeter system operated up to kilohertz frequencies and 7 V rms. A 10 V programmable Josephson voltage standard (PJVS) array was installed on a pulse tube cooler (PTC) driven with a 4 kW air-cooled compressor. The operating margins at 70 GHz frequencies were investigated in detail and found to exceed 1 mA Shapiro step width. A key factor for the successful chip operation was the low on-chip power consumption of 65 mW in total. A thermal interface between PJVS chip and PTC cold stage was used to avoid a significant chip overheating. By installing the cryocooled PJVS array into an AC quantum voltmeter setup, several calibration measurements of dc standards and calibrator ac voltages up to 2 kHz frequencies were carried out to demonstrate the full functionality. The results are discussed and compared to systems with standard liquid helium cooling. For dc voltages, a direct comparison measurement between the dry-cooled AC quantum voltmeter and a liquid-helium based 10 V PJVS shows an agreement better than 1 part in 1010.

  14. Bi-directional flow induced by an AC electroosmotic micropump with DC voltage bias.

    PubMed

    Islam, Nazmul; Reyna, Jairo

    2012-04-01

    This paper discusses the principle of biased alternating current electroosmosis (ACEO) and its application to move the bulk fluid in a microchannel, as an alternative to mechanical pumping methods. Previous EO-driven flow research has looked at the effect of electrode asymmetry and transverse traveling wave forms on the performance of electroosmotic pumps. This paper presents an analysis that was conducted to assess the effect of combining an AC signal with a DC (direct current) bias when generating the electric field needed to impart electroosmosis (EO) within a microchannel. The results presented here are numerical and experimental. The numerical results were generated through simulations performed using COMSOL 3.5a. Currently available theoretical models for EO flows were embedded in the software and solved numerically to evaluate the effects of channel geometry, frequency of excitation, electrode array geometry, and AC signal with a DC bias on the flow imparted on an electrically conducting fluid. Simulations of the ACEO flow driven by a constant magnitude of AC voltage over symmetric electrodes did not indicate relevant net flows. However, superimposing a DC signal over the AC signal on the same symmetric electrode array leads to a noticeable net forward flow. Moreover, changing the polarity of electrical signal creates a bi-directional flow on symmetrical electrode array. Experimental flow measurements were performed on several electrode array configurations. The mismatch between the numerical and experimental results revealed the limitations of the currently available models for the biased EO. However, they confirm that using a symmetric electrode array excited by an AC signal with a DC bias leads to a significant improvement in flow rates in comparison to the flow rates obtained in an asymmetric electrode array configuration excited just with an AC signal.

  15. Synthesis and characterization of soluble conducting polymers and conducting adhesives

    NASA Astrophysics Data System (ADS)

    Oztemiz, Serhan

    With the demanding nature of the technology today, scientists are looking for new materials in order to decrease the cost, increase the efficiency of the use of the materials, and decrease time-consuming steps in order to increase the speed of production. New materials are being studied to decrease the weight of cars, planes and space vehicles; surface properties are being modified to decrease the drag coefficient; new technologies are being introduced for speeding up applications in production and assembly lines. In this research we address the needs of different technological applications from a conductivity perspective. In the first part of the thesis, the synthesis of soluble conducting polymers in order to make them more processable for potential electronic and photovoltaic applications is presented. Soluble conducting polymers of 3-hexylthiophene, 3-octylthiophene, 3-decylthiophene and 3-dodecylthiophene were synthesized electrochemically and thus, doped during synthesis. It was found that the conductivities; molecular weights and degrees of polymerization of the polymers strongly depend on the side chain's length. The substitution of alkyl side chains decreases the reactivity of the growing chain, and with an increasing side-chain length, all of these properties show a decrease. The hexyl substituent, being the shortest of the four side chains, causes the least distortion in the background, has the highest conjugation, and has the highest shift in the UV spectrum when it polymerizes. As the length of the side chain increases, the shift in the UV spectrum decreases, too. Decrease in the pi-stacking, conjugation and delocalization decreases the conductivity. This gives the material an opportunity to be used in photovoltaic applications. In the second part of the thesis, a conducting adhesive formulation that eliminates the need for heat or other expensive and rather bothersome application methods to activate the adhesive is investigated. Using the quick

  16. Long-range response in ac electricity grids.

    PubMed

    Jung, Daniel; Kettemann, Stefan

    2016-07-01

    Local changes in the topology of electricity grids can cause overloads far away from the disturbance [D. Witthaut and M. Timme, Eur. Phys. J. B 86, 377 (2013)EPJBFY1434-602810.1140/epjb/e2013-40469-4], making the prediction of the robustness against changes in the topology-for example, caused by power outages or grid extensions-a challenging task. The impact of single-line additions on the long-range response of dc electricity grids has recently been studied [D. Labavić, R. Suciu, H. Meyer-Ortmanns, and S. Kettemann, Eur. Phys. J.: Spec. Top. 223, 2517 (2014)1951-635510.1140/epjst/e2014-02273-0]. By solving the real part of the static ac load flow equations, we conduct a similar investigation for ac grids. In a regular two-dimensional grid graph with cyclic boundary conditions, we find a power law decay for the change of power flow as a function of distance to the disturbance over a wide range of distances. The power exponent increases and saturates for large system sizes. By applying the same analysis to the German transmission grid topology, we show that also in real-world topologies a long-ranged response can be found.

  17. Long-range response in ac electricity grids

    NASA Astrophysics Data System (ADS)

    Jung, Daniel; Kettemann, Stefan

    2016-07-01

    Local changes in the topology of electricity grids can cause overloads far away from the disturbance [D. Witthaut and M. Timme, Eur. Phys. J. B 86, 377 (2013), 10.1140/epjb/e2013-40469-4], making the prediction of the robustness against changes in the topology—for example, caused by power outages or grid extensions—a challenging task. The impact of single-line additions on the long-range response of dc electricity grids has recently been studied [D. Labavić, R. Suciu, H. Meyer-Ortmanns, and S. Kettemann, Eur. Phys. J.: Spec. Top. 223, 2517 (2014), 10.1140/epjst/e2014-02273-0]. By solving the real part of the static ac load flow equations, we conduct a similar investigation for ac grids. In a regular two-dimensional grid graph with cyclic boundary conditions, we find a power law decay for the change of power flow as a function of distance to the disturbance over a wide range of distances. The power exponent increases and saturates for large system sizes. By applying the same analysis to the German transmission grid topology, we show that also in real-world topologies a long-ranged response can be found.

  18. Numerical study of dc-biased ac-electrokinetic flow over symmetrical electrodes

    PubMed Central

    Yang Ng, Wee; Ramos, Antonio; Cheong Lam, Yee; Rodriguez, Isabel

    2012-01-01

    This paper presents a numerical study of DC-biased AC-electrokinetic (DC-biased ACEK) flow over a pair of symmetrical electrodes. The flow mechanism is based on a transverse conductivity gradient created through incipient Faradaic reactions occurring at the electrodes when a DC-bias is applied. The DC biased AC electric field acting on this gradient generates a fluid flow in the form of vortexes. To understand more in depth the DC-biased ACEK flow mechanism, a phenomenological model is developed to study the effects of voltage, conductivity ratio, channel width, depth, and aspect ratio on the induced flow characteristics. It was found that flow velocity on the order of mm/s can be produced at higher voltage and conductivity ratio. Such rapid flow velocity is one of the highest reported in microsystems technology using electrokinetics. PMID:22662084

  19. Laser Raman and ac impedance spectroscopic studies of PVA: NH 4NO 3 polymer electrolyte

    NASA Astrophysics Data System (ADS)

    Hema, M.; Selvasekarapandian, S.; Hirankumar, G.; Sakunthala, A.; Arunkumar, D.; Nithya, H.

    2010-01-01

    Ion conducting polymer electrolyte PVA:NH 4NO 3 has been prepared by solution casting technique and characterized using XRD, Raman and ac impedance spectroscopic analyses. The amorphous nature of the polymer films has been confirmed by XRD and Raman spectroscopy. An insight into the deconvoluted Raman peaks of υ1 vibration of NO 3- anion for the polymer electrolyte reveals the dominancy of ion aggregates at higher NH 4NO 3 concentration. From the ac impedance studies, the highest ion conductivity at 303 K has been found to be 7.5 × 10 -3 S cm -1 for 80PVA:20NH 4NO 3. The conductivity of the polymer electrolytes has been found to depend on the degree of dissociation of the salt in the host polymer matrix. The combination of the above-mentioned analyses has proven worth while and in fact necessary in order to achieve better understanding of these complex systems.

  20. Spectrum-RG astrophysical project

    NASA Astrophysics Data System (ADS)

    Pavlinsky, M.; Sunyaev, R.; Churazov, E.; Vikhlinin, A.; Sazonov, S.; Revnivtsev, M.; Arefiev, V.; Lapshov, I.; Akimov, V.; Levin, V.; Buntov, M.; Semena, N.; Grigorovich, S.; Babyshkin, V.; Predehl, P.; Hasinger, G.; Böhringer, H.; Schmitt, J.; Santangelo, A.; Schwope, A.; Wilms, J.

    2009-08-01

    The Spectrum-Roentgen-Gamma mission will be launched in the 2012 year into a L2 orbit with Soyuz launcher and Fregat buster from Baikonur. The mission will conduct all-sky survey with X-ray mirror telescopes eROSITA and ART-XC up to 11 keV. It will allow detection of about 100 thousand clusters of galaxies and discovery large scale Universe structure. It will also discover all obscured accreting Black Holes in nearby galaxies and many (about 3 millions) new distant AGN. Then it is planned to observe dedicated sky regions with high sensitivity and thereafter to perform follow-up pointed observations of selected sources.

  1. Spread Spectrum Frequency Management

    DTIC Science & Technology

    1989-06-01

    theoretically predicted behavior of the new system. Thp experimental program must include field tests in real propagation and interference environments...technological developments and without adequate overall knowledge of propagation characteristics or of other important uses that might require... propagation characteristics at the different frequency levels. The history of major spectrum allocations is then a 7 record of decisions primarily

  2. Stellar Spectrum Synthesizer

    ERIC Educational Resources Information Center

    Landegren, G. F.

    1975-01-01

    Describes a device which employs two diffraction gratings and three or four simple lenses to produce arbitrary absorption or emission spectra that may be doppler shifted and spectroscopically examined by students some distance away. It may be regarded as a sort of artificial star whose spectrum may be analyzed as an undergraduate laboratory…

  3. The Frequency Spectrum Radio.

    ERIC Educational Resources Information Center

    Howkins, John, Ed.

    1979-01-01

    This journal issue focuses on the frequency spectrum used in radio communication and on the World Administrative Radio Conference, sponsored by the International Telecommunication Union, held in Geneva, Switzerland, in the fall of 1979. Articles describe the World Administrative Radio Conference as the most important radio communication conference…

  4. Battlefield spectrum management

    NASA Astrophysics Data System (ADS)

    Sivakumar, C.

    1997-06-01

    Modern tactical communications systems rely on radios to support network and user connectivity. One of the challenges for network planners and managers is to make best use of scarce and vulnerable frequency spectrum resources to support the communication needs of war fighters. With the wide variety of Iris radio types typically to be deployed in the battlefield (ranging from high frequency to super high frequency), a comprehensive suite of tools is necessary to ensure that frequency interference is kept minimum. Without a sophisticated frequency spectrum management system, the most advanced tactical communications systems could be rendered useless, jeopardizing human life and national security. For these reasons, it is important to develop an Iris wide battlefield spectrum management capability that takes full advantage of current frequency spectrum management research and development (R&D), related tools, and supporting technology for assigning frequencies. This session briefly describes various assignment strategies being adopted in the Iris BFSM for overcoming cosite/collocated/farsite interferences along with the propagation models [from high frequency (HF) to super high frequency (SHF)] used for the assignment of frequencies. Also a brief thread outlining the process for generating frequency allocation/assignment request and analysis of frequency interference is discussed.

  5. 48 CFR Appendixes A-C to Chapter 7 - [Reserved

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 48 Federal Acquisition Regulations System 5 2010-10-01 2010-10-01 false A Appendixes A-C to Chapter 7 Federal Acquisition Regulations System AGENCY FOR INTERNATIONAL DEVELOPMENT Appendixes A-C to Chapter 7...

  6. 48 CFR Appendixes A-C to Chapter 7 - [Reserved

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 48 Federal Acquisition Regulations System 5 2014-10-01 2014-10-01 false A Appendixes A-C to Chapter 7 Federal Acquisition Regulations System AGENCY FOR INTERNATIONAL DEVELOPMENT Appendixes A-C to Chapter 7...

  7. Conformational influence on the hopping conductivity in pig insulin

    NASA Astrophysics Data System (ADS)

    Ye, Yuan-Jie; Ladik, János

    1995-05-01

    The ac conductivity of pig insulin has been reported previously [Y.-J. Ye and J. Ladik, Phys. Rev. B 48, 5120 (1993); Int. J. Quantum Chem. 52, 491 (1994)]. Now we have calculated in the ab initio scheme using Clementi's minimal basis set and the random-walk theory of Lax and co-workers the ac conductivity in another conformation that occurs in the same crystal. The results confirm the conclusions of the previous papers, that is, native proteins can be good amorphous semiconductors if they are doped. The comparison of the results of the two conformations of pig insulin shows that the ac conductivity changes two orders of magnitude in the frequency range that corresponds to the time period of the elementary steps of chemical reactions (ω>1010 sec-1) when the three-dimensional structure changes. However, it does not change significantly in the low-frequency range (ω<104 sec-1). The conclusion is that in the high-frequency range insulin would change both the ac conductivity of itself and its receptor if it binds to a receptor. Thus insulin might change the electron transport in the receptor when it expresses its biological activity.

  8. AC Electric Field Activated Shape Memory Polymer Composite

    NASA Technical Reports Server (NTRS)

    Kang, Jin Ho; Siochi, Emilie J.; Penner, Ronald K.; Turner, Travis L.

    2011-01-01

    Shape memory materials have drawn interest for applications like intelligent medical devices, deployable space structures and morphing structures. Compared to other shape memory materials like shape memory alloys (SMAs) or shape memory ceramics (SMCs), shape memory polymers (SMPs) have high elastic deformation that is amenable to tailored of mechanical properties, have lower density, and are easily processed. However, SMPs have low recovery stress and long response times. A new shape memory thermosetting polymer nanocomposite (LaRC-SMPC) was synthesized with conductive fillers to enhance its thermo-mechanical characteristics. A new composition of shape memory thermosetting polymer nanocomposite (LaRC-SMPC) was synthesized with conductive functionalized graphene sheets (FGS) to enhance its thermo-mechanical characteristics. The elastic modulus of LaRC-SMPC is approximately 2.7 GPa at room temperature and 4.3 MPa above its glass transition temperature. Conductive FGSs-doped LaRC-SMPC exhibited higher conductivity compared to pristine LaRC SMP. Applying an electric field at between 0.1 Hz and 1 kHz induced faster heating to activate the LaRC-SMPC s shape memory effect relative to applying DC electric field or AC electric field at frequencies exceeding1 kHz.

  9. AC losses in a HTS coil carrying DC current in AC external magnetic field

    NASA Astrophysics Data System (ADS)

    Ogawa, J.; Zushi, Y.; Fukushima, M.; Tsukamoto, O.; Suzuki, E.; Hirakawa, M.; Kikukawa, K.

    2003-10-01

    We electrically measured AC losses in a Bi2223/Ag-sheathed pancake coil excited by a DC current in AC external magnetic field. Losses in the coil contain two kinds of loss components that are the magnetization losses and dynamic resistance losses. In the measurement, current leads to supply a current to the coil were specially arranged to suppress electromagnetic coupling between the coil current and the AC external magnetic field. A double pick-up coils method was used to suppress a large inductive voltage component contained in voltage signal for measuring the magnetization losses. It was observed that the magnetization losses were dependent on the coil current and that a peak of a curve of the loss factor vs. amplitude of the AC external magnetic field shifted to lower amplitude of the AC magnetic field as the coil current increased. This result suggests the full penetration magnetic field of the coil tape decreases as the coil current increases. The dynamic resistance losses were measured by measuring a DC voltage appearing between the coil terminals. It was observed that the DC voltage appearing in the coil subject to the AC external magnetic field was much larger than that in the coil subject to DC magnetic field.

  10. Energy spectrum of corona impulses generated from insulated wires under high a.c. voltages

    NASA Technical Reports Server (NTRS)

    Doreswamy, C. V.; Padiyar, K. R.; Crowell, C. S.

    1978-01-01

    This paper suggests methods for calculating spectral energy densities of corona impulses generated from insulated conductors. The calculation is based on the data obtained from the measurement of corona pulse waveforms, repetition rates and relevant statistical properties of corona impulses.

  11. Non-Antithrombotic Medical Options in ACS: Old Agents and New Lines on the Horizon

    PubMed Central

    Soukoulis, Victor; Boden, William E.; Smith, Sidney C.; O'Gara, Patrick T.

    2014-01-01

    Acute coronary syndromes (ACS) constitute a spectrum of clinical presentations ranging from unstable angina and non-ST-segment elevation myocardial infarction to ST-segment myocardial infarction. Myocardial ischemia in this context occurs as a result of an abrupt decrease in coronary blood flow and resultant imbalance in the myocardial oxygen supply-demand relationship. Coronary blood flow is further compromised by other mechanisms that increase coronary vascular resistance or reduce coronary driving pressure. The goals of treatment are to decrease myocardial oxygen demand, increase coronary blood flow and oxygen supply, and limit myocardial injury. Treatments are generally divided into “disease-modifying” agents or interventions that improve hard clinical outcomes and other strategies that can reduce ischemia. In addition to traditional drugs such as beta-blockers and inhibitors of the reninangiotensin-aldosterone system, newer agents have expanded the number of molecular pathways targeted for treatment of ACS. Ranolazine, trimetazidine, nicorandil, and ivabradine are medications that have been shown to reduce myocardial ischemia through diverse mechanisms and have been tested in limited fashion in patients with ACS. Attenuating the no-reflow phenomenon and reducing the injury compounded by acute reperfusion after a period of coronary occlusion are active areas of research. Additionally, interventions aimed at ischemic pre- and post-conditioning may be useful means by which to limit myocardial infarct size. Trials are also underway to examine altered metabolic and oxygen-related pathways in ACS. This review will discuss traditional and newer anti-ischemic therapies for patients with ACS, exclusive of revascularization, anti-thrombotic agents, and the use of high-intensity statins. PMID:24902977

  12. Increased Long-Flight Activity Triggered in Beet Armyworm by Larval Feeding on Diet Containing Cry1Ac Protoxin

    PubMed Central

    Jiang, Xing Fu; Chen, Jian; Zhang, Lei; Sappington, Thomas W.; Luo, Li Zhi

    2013-01-01

    Evaluating ecological safety and conducting pest risk analysis for transgenic crops are vitally important before their commercial planting. The beet armyworm, Spodoptera exigua, a long-distance migratory insect pest, is not a direct target of transgenic Cry1Ac-expressing cotton in China, but nevertheless it has recently become an important pest. Migrants leaving their natal field arrive in other appropriate habitat far away in a short time, often followed by larval outbreaks. S. exigua has low susceptibility to Cry1Ac. However, our results from laboratory experiments identified (i) sublethal effects of Cry1Ac protoxin on larval development rate, larval and pupal weight, and adult lifetime fecundity, and (ii) increased long-flight behavior triggered by Cry1Ac which may contribute to larval outbreaks elsewhere. No significant differences in larval mortality, pupation rate, adult emergence rate, longevity, pre-oviposition period, or oviposition period were observed between controls and larvae fed on artificial diet incorporating a low concentration of Cry1Ac protoxin. The negative sublethal effects on some developmental and reproductive traits and lack of effect on others suggest they do not contribute to the observed severity of S. exigua outbreaks after feeding on Cry1Ac cotton. Interestingly, the percentage of long fliers increased significantly when larvae were reared on diet containing either of two low-dose treatments of Cry1Ac, suggesting a possible increased propensity to disperse long distances triggered by Cry1Ac. We hypothesize that negative effects on development and reproduction caused by Cry1Ac in the diet are offset by increased flight propensity triggered by the poor food conditions, thereby improving the chances of escaping adverse local conditions before oviposition. Increased long-flight propensity in turn may amplify the area damaged by outbreak populations. This phenomenon might be common in other migratory insect pests receiving sublethal doses

  13. CROSS-DISCIPLINARY PHYSICS AND RELATED AREAS OF SCIENCE AND TECHNOLOGY: Characteristics of alternating current hopping conductivity in DNA sequences

    NASA Astrophysics Data System (ADS)

    Ma, Song-Shan; Xu, Hui; Wang, Huan-You; Guo, Rui

    2009-08-01

    This paper presents a model to describe alternating current (AC) conductivity of DNA sequences, in which DNA is considered as a one-dimensional (1D) disordered system, and electrons transport via hopping between localized states. It finds that AC conductivity in DNA sequences increases as the frequency of the external electric field rises, and it takes the form of øac(ω) ~ ω2 ln2(1/ω). Also AC conductivity of DNA sequences increases with the increase of temperature, this phenomenon presents characteristics of weak temperature-dependence. Meanwhile, the AC conductivity in an off-diagonally correlated case is much larger than that in the uncorrelated case of the Anderson limit in low temperatures, which indicates that the off-diagonal correlations in DNA sequences have a great effect on the AC conductivity, while at high temperature the off-diagonal correlations no longer play a vital role in electric transport. In addition, the proportion of nucleotide pairs p also plays an important role in AC electron transport of DNA sequences. For p < 0.5, the conductivity of DNA sequence decreases with the increase of p, while for p >= 0.5, the conductivity increases with the increase of p.

  14. The Cryogenic Anti-Coincidence detector for ATHENA X-IFU: pulse analysis of the AC-S7 single pixel prototype

    NASA Astrophysics Data System (ADS)

    D'Andrea, M.; Argan, A.; Lotti, S.; Macculi, C.; Piro, L.; Biasotti, M.; Corsini, D.; Gatti, F.; Torrioli, G.

    2016-07-01

    The ATHENA observatory is the second large-class mission in ESA Cosmic Vision 2015-2025, with a launch foreseen in 2028 towards the L2 orbit. The mission addresses the science theme "The Hot and Energetic Universe", by coupling a high-performance X-ray Telescope with two complementary focal-plane instruments. One of these is the X-ray Integral Field Unit (X-IFU): it is a TES based kilo-pixel order array able to provide spatially resolved high-resolution spectroscopy (2.5 eV at 6 keV) over a 5 arcmin FoV. The X-IFU sensitivity is degraded by the particles background expected at L2 orbit, which is induced by primary protons of both galactic and solar origin, and mostly by secondary electrons. To reduce the background level and enable the mission science goals, a Cryogenic Anticoincidence (CryoAC) detector is placed < 1 mm below the TES array. It is a 4- pixel TES based detector, with wide Silicon absorbers sensed by Ir:Au TESes. The CryoAC development schedule foresees by Q1 2017 the delivery of a Demonstration Model (DM) to the X-IFU FPA development team. The DM is a single-pixel detector that will address the final design of the CryoAC. It will verify some representative requirements at single-pixel level, especially the detector operation at 50 mK thermal bath and the threshold energy at 20 keV. To reach the final DM design we have developed and tested the AC-S7 prototype, with 1 cm2 absorber area sensed by 65 Ir TESes. Here we will discuss the pulse analysis of this detector, which has been illuminated by the 60 keV line from a 241Am source. First, we will present the analysis performed to investigate pulses timings and spectrum, and to disentangle the athermal component of the pulses from the thermal one. Furthermore, we will show the application to our dataset of an alternative method of pulse processing, based upon Principal Component Analysis (PCA). This kind of analysis allow us to recover better energy spectra than achievable with traditional methods

  15. 7 CFR 1737.31 - Area Coverage Survey (ACS).

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 7 Agriculture 11 2012-01-01 2012-01-01 false Area Coverage Survey (ACS). 1737.31 Section 1737.31... Studies-Area Coverage Survey and Loan Design § 1737.31 Area Coverage Survey (ACS). (a) The Area Coverage Survey (ACS) is a market forecast of service requirements of subscribers in a proposed service area....

  16. 7 CFR 1737.31 - Area Coverage Survey (ACS).

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 7 Agriculture 11 2010-01-01 2010-01-01 false Area Coverage Survey (ACS). 1737.31 Section 1737.31... Studies-Area Coverage Survey and Loan Design § 1737.31 Area Coverage Survey (ACS). (a) The Area Coverage Survey (ACS) is a market forecast of service requirements of subscribers in a proposed service area....

  17. 7 CFR 1737.31 - Area Coverage Survey (ACS).

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 7 Agriculture 11 2013-01-01 2013-01-01 false Area Coverage Survey (ACS). 1737.31 Section 1737.31... Studies-Area Coverage Survey and Loan Design § 1737.31 Area Coverage Survey (ACS). (a) The Area Coverage Survey (ACS) is a market forecast of service requirements of subscribers in a proposed service area....

  18. 7 CFR 1737.31 - Area Coverage Survey (ACS).

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 7 Agriculture 11 2011-01-01 2011-01-01 false Area Coverage Survey (ACS). 1737.31 Section 1737.31... Studies-Area Coverage Survey and Loan Design § 1737.31 Area Coverage Survey (ACS). (a) The Area Coverage Survey (ACS) is a market forecast of service requirements of subscribers in a proposed service area....

  19. 21 CFR 880.5500 - AC-powered patient lift.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 8 2011-04-01 2011-04-01 false AC-powered patient lift. 880.5500 Section 880.5500 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED... Devices § 880.5500 AC-powered patient lift. (a) Identification. An AC-powered lift is an...

  20. Methods for Addressing Missing Data with Applications from ACS Exams

    ERIC Educational Resources Information Center

    Brandriet, Alexandra; Holme, Thomas

    2015-01-01

    As part of the ACS Examinations Institute (ACS-EI) national norming process, student performance data sets are collected from professors at colleges and universities from around the United States. Because the data sets are collected on a volunteer basis, the ACS-EI often receives data sets with only students' total scores and without the students'…

  1. Theoretical and experimental study of meniscus behavior under AC electric field for Electrohydrodynamic (EHD) jetting

    NASA Astrophysics Data System (ADS)

    Tran, Si Bui Quang; Byun, Doyoung

    2009-11-01

    The electrohydrodynamic (EHD) spraying technique has been utilized in applications such as inkjet printing and mass spectrometry technologies. In this paper, the role of electrical potential signals in jetting and on the oscillation of the meniscus is evaluated. The jetting and meniscus oscillation behavior are experimentally investigated under ac voltage, ac voltage superimposed on dc voltage, and pulsed dc voltage. Furthermore, the analytical simulation about the oscillation of an anchored edge hemispherical meniscus located on a conductive flat plate under a uniform ac electric field is presented. The mutual interaction between the electric field and the hydrodynamics is iteratively solved. As a result, the simulation can calculate the meniscus shapes, contours of voltage outside the meniscus and the velocity profile of liquid inside the meniscus during the period of the oscillation according to the applied frequency. Based on the present theory, one can predict the oscillation mode with a certain applied frequency. The present theory can also be applied to investigate the oscillation of a free conductive drop in a uniform ac electric field.

  2. Micro pumping methods based on AC electrokinetics and Electrorheologically actuated PDMS valves

    NASA Astrophysics Data System (ADS)

    Soni, Gaurav; Squires, Todd; Meinhart, Carl

    2006-11-01

    We have developed 2 different micropumping methods for transporting ionic fluids through microchannels. The first method is based on Induced Charge Electroosmosis (ICEO) and AC flow field-effect. We used an AC electric field to produce a symmetric ICEO flow on a planar electrode, called `gate'. In order to break the symmetry of ICEO, we applied an additional AC voltage to the gate electrode. Such modulation of the gate potential is called field effect and produces a unidirectional pumping over the gate surface. We used micro PIV to measure pumping velocities for a range of ionic concentration, AC frequency and gate voltage. We have also conducted numerical simulations to understand the deteriorating effect of lateral conduction of surface charge on the pumping velocities. The second method is based on vibration of a flexible PDMS diaphragm actuated by an electrorheological (ER) fluid. ER fluid is a colloidal suspension exhibiting a reversible liquid-to-solid transition under an electric field. This liquid-to-solid transition can yield very high shear stress and can be used to open and close a PDMS valve. Three such valves were fabricated and actuated in a peristaltic fashion in order to achieve positive displacement pumping of fluids.

  3. Charge transport and ac response under light illumination in gate-modulated DNA molecular junctions.

    PubMed

    Zhang, Yan; Zhu, Wen-Huan; Ding, Guo-Hui; Dong, Bing; Wang, Xue-Feng

    2015-05-22

    Using a two-strand tight-binding model and within nonequilibrium Green's function approach, we study charge transport through DNA sequences (GC)NGC and (GC)1(TA)NTA (GC)3 sandwiched between two Pt electrodes. We show that at low temperature DNA sequence (GC)NGC exhibits coherent charge carrier transport at very small bias, since the highest occupied molecular orbital in the GC base pair can be aligned with the Fermi energy of the metallic electrodes by a gate voltage. A weak distance dependent conductance is found in DNA sequence (GC)1(TA)NTA (GC)3 with large NTA. Different from the mechanism of thermally induced hopping of charges proposed by the previous experiments, we find that this phenomenon is dominated by quantum tunnelling through discrete quantum well states in the TA base pairs. In addition, ac response of this DNA junction under light illumination is also investigated. The suppression of ac conductances of the left and right lead of DNA sequences at some particular frequencies is attributed to the excitation of electrons in the DNA to the lead Fermi surface by ac potential, or the excitation of electrons in deep DNA energy levels to partially occupied energy levels in the transport window. Therefore, measuring ac response of DNA junctions can reveal a wealth of information about the intrinsic dynamics of DNA molecules.

  4. An AC drive system for a battery driven moped

    SciTech Connect

    Nandi, S.; Saha, S.; Sharon, M.; Sundersingh, V.P.

    1995-12-31

    A petrol driven moped is converted to an electric one by replacing the petrol engine by a three phase 1.5 HR, AC squirrel cage induction motor drive system. The motor voltage rating selected is 200 V to keep the DC boost voltage level to a reasonable value.f the power source used is a high energy density, 24 V, 110 Ah, Ni-Zn battery. A modified indirect current controlled step-up chopper as well as a standard push-pull DC-DC boost converter is studied for the boost scheme. A simple three phase quasi-square wave inverter is designed along with suitable protection for driving the motor. Successful trial test of the system has been conducted at the laboratory.

  5. Conducting polymer transistors making use of activated carbon gate electrodes.

    PubMed

    Tang, Hao; Kumar, Prajwal; Zhang, Shiming; Yi, Zhihui; Crescenzo, Gregory De; Santato, Clara; Soavi, Francesca; Cicoira, Fabio

    2015-01-14

    The characteristics of the gate electrode have significant effects on the behavior of organic electrochemical transistors (OECTs), which are intensively investigated for applications in the booming field of organic bioelectronics. In this work, high specific surface area activated carbon (AC) was used as gate electrode material in OECTs based on the conducting polymer poly(3,4-ethylenedioxythiophene) (PEDOT) doped with poly(styrenesulfonate) (PSS). We found that the high specific capacitance of the AC gate electrodes leads to high drain-source current modulation in OECTs, while their intrinsic quasi-reference characteristics make unnecessary the presence of an additional reference electrode to monitor the OECT channel potential.

  6. A geomagnetic field spectrum

    NASA Technical Reports Server (NTRS)

    Langel, R. A.; Estes, R. H.

    1982-01-01

    A spherical harmonic model of the earth's internal magnetic field of degree and order 23 is derived from selected Magsat data, and its power spectrum, computed with terms developed by Mauersberger (1956) and Lowes (1974), is found to exhibit a change of a slope at n = 14 which is interpreted as an indication that the core field dominates at values lower than 13 while the crust field dominates above a value of 15. The representations of the two portions of the spectrum obtained can be used to establish order-of-magnitude inaccuracies due to both crustal fields and the inability to observe core field wavelengths beyond n = 13, at which point they are obscured by the crustal field, in core field models.

  7. Spread spectrum image steganography.

    PubMed

    Marvel, L M; Boncelet, C R; Retter, C T

    1999-01-01

    In this paper, we present a new method of digital steganography, entitled spread spectrum image steganography (SSIS). Steganography, which means "covered writing" in Greek, is the science of communicating in a hidden manner. Following a discussion of steganographic communication theory and review of existing techniques, the new method, SSIS, is introduced. This system hides and recovers a message of substantial length within digital imagery while maintaining the original image size and dynamic range. The hidden message can be recovered using appropriate keys without any knowledge of the original image. Image restoration, error-control coding, and techniques similar to spread spectrum are described, and the performance of the system is illustrated. A message embedded by this method can be in the form of text, imagery, or any other digital signal. Applications for such a data-hiding scheme include in-band captioning, covert communication, image tamperproofing, authentication, embedded control, and revision tracking.

  8. Radio frequency spectrum management

    NASA Astrophysics Data System (ADS)

    Sujdak, E. J., Jr.

    1980-03-01

    This thesis is a study of radio frequency spectrum management as practiced by agencies and departments of the Federal Government. After a brief introduction to the international agency involved in radio frequency spectrum management, the author concentrates on Federal agencies engaged in frequency management. These agencies include the National Telecommunications and Information Administration (NTIA), the Interdepartment Radio Advisory Committee (IRAC), and the Department of Defense (DoD). Based on an analysis of Department of Defense frequency assignment procedures, recommendations are given concerning decentralizing military frequency assignment by delegating broader authority to unified commanders. This proposal includes a recommendation to colocate the individual Service frequency management offices at the Washington level. This would result in reduced travel costs, lower manpower requirements, and a common tri-Service frequency management data base.

  9. Multitaper Spectrum Estimates

    NASA Astrophysics Data System (ADS)

    Fodor, I. K.; Stark, P. B.

    Multitapering is a statistical technique developed to improve on the notorious periodogram estimate of the power spectrum (Thomson, 1982; Percival, Walden 1993). We show how to obtain orthogonal tapers for time series observed with gaps, and how to use statistical resampling techniques (Efron, Tibshirani 1993) to calculate realistic uncertainty estimates for multitaper estimates. We introduce multisegment multitapering. Multitapering can also be extended to the 2D case. We indicate how to construct tapers that minimize the spatial leakage in estimates of the spherical harmonic decomposition of the velocity images. Spatial multitapering followed by the temporal tapering of the estimated spherical harmonic time series is expected to result in improved spectrum and subsequent solar oscillation mode parameter estimates.

  10. Absorption of ac fields in amorphous indium-oxide films

    SciTech Connect

    Ovadyahu, Z.

    2014-08-20

    Absorption data from applied ac fields in Anderson-localized amorphous indium-oxide (In{sub x}O) films are shown to be frequency and disorder dependent. The absorption shows a roll-off at a frequency which is much lower than the electron-electron scattering rate of the material when it is in the diffusive regime. This is interpreted as evidence for discreteness of the energy spectrum of the deeply localized regime. This is consistent with recent many-body localization scenarios. As the metal-insulator transition is approached, the absorption shifts to higher frequencies. Comparing with the previously obtained results on the crystalline version of indium-oxide (In{sub 2}O{sub 3−x}) implies a considerably higher inelastic electron-phonon scattering rate in the amorphous material. The range over which the absorption versus frequency decreases may indicate that a wide distribution of localization length is a common feature in these systems.

  11. The ac and dc performance of polymeric insulating materials under accelerated aging in a fog chamber

    SciTech Connect

    Gorur, R.S. ); Cherney, E.A. ); Hackam, R. )

    1988-10-01

    The paper presents the results of the dc performance of polymeric insulating materials in a fog chamber. The materials evaluated in fog produced from low (250 ..mu..S/cm) and high (1000 ..mu..S/cm) conductivity water include cylindrical rod samples of high temperature vulcanized (HTV) silicone rubber and ethylene propylene diene monomer (EPDM) rubber containing various amounts of either alumina trihydrate (ATH) or silica fillers, or both. Comparison is made of material performance obtained with ac which was reported in an earlier study. In both low and high conductivity fog, the time to failure with ac and +dc was very similar, but a reduction by a factor of about four was observed in the time to failure with -dc. For both ac and dc, silicone rubber performed better than EPDM samples in low conductivity fog, while the order of performance was reversed in high conductivity fog. A theoretical model to determine the effect of dry band discharges on material is presented. Good agreement of the predicted behavior of materials with the experimental findings is shown.

  12. The marine diversity spectrum.

    PubMed

    Reuman, Daniel C; Gislason, Henrik; Barnes, Carolyn; Mélin, Frédéric; Jennings, Simon

    2014-07-01

    Distributions of species body sizes within a taxonomic group, for example, mammals, are widely studied and important because they help illuminate the evolutionary processes that produced these distributions. Distributions of the sizes of species within an assemblage delineated by geography instead of taxonomy (all the species in a region regardless of clade) are much less studied but are equally important and will illuminate a different set of ecological and evolutionary processes. We develop and test a mechanistic model of how diversity varies with body mass in marine ecosystems. The model predicts the form of the 'diversity spectrum', which quantifies the distribution of species' asymptotic body masses, is a species analogue of the classic size spectrum of individuals, and which we have found to be a new and widely applicable description of diversity patterns. The marine diversity spectrum is predicted to be approximately linear across an asymptotic mass range spanning seven orders of magnitude. Slope -0.5 is predicted for the global marine diversity spectrum for all combined pelagic zones of continental shelf seas, and slopes for large regions are predicted to lie between -0.5 and -0.1. Slopes of -0.5 and -0.1 represent markedly different communities: a slope of -0.5 depicts a 10-fold reduction in diversity for every 100-fold increase in asymptotic mass; a slope of -0.1 depicts a 1.6-fold reduction. Steeper slopes are predicted for larger or colder regions, meaning fewer large species per small species for such regions. Predictions were largely validated by a global empirical analysis. Results explain for the first time a new and widespread phenomenon of biodiversity. Results have implications for estimating numbers of species of small asymptotic mass, where taxonomic inventories are far from complete. Results show that the relationship between diversity and body mass can be explained from the dependence of predation behaviour, dispersal, and life history on

  13. Radio spectrum surveillance station

    NASA Technical Reports Server (NTRS)

    Hersey, D. R.

    1979-01-01

    The paper presents a general and functional description of a low-cost surveillance station designed as the first phase of NASA's program to develop a radio spectrum surveillance capability for deep space stations for identifying radio frequency interference sources. The station described has identified several particular interferences and is yielding spectral signature data which, after cataloging, will serve as a library for rapid identification of frequently observed interference. Findings from the use of the station are discussed.

  14. Large aperture ac interferometer for optical testing.

    PubMed

    Moore, D T; Murray, R; Neves, F B

    1978-12-15

    A 20-cm clear aperture modified Twyman-Green interferometer is described. The system measures phase with an AC technique called phase-lock interferometry while scanning the aperture with a dual galvanometer scanning system. Position information and phase are stored in a minicomputer with disk storage. This information is manipulated with associated software, and the wavefront deformation due to a test component is graphically displayed in perspective and contour on a CRT terminal.

  15. YBCO Coated Conductors with Reduced AC Losses

    DTIC Science & Technology

    2008-01-30

    application such as turbo- generators and gyrotron magnets . The major reason is the enhanced in-field performance at 50-65 K and the proven...transformers, current limiters and the stators of rotating equipment. Low AC-loss in 2G HTS requires wire components with low magnetism , and an YBCO...layer with low transport and low hysteretic losses in an alternating magnetic field. The latter loss type requires a suitable filamentization technique

  16. AC plasma anemometer—characteristics and design

    NASA Astrophysics Data System (ADS)

    Marshall, Curtis; Matlis, Eric; Corke, Thomas; Gogineni, Sivaram

    2015-08-01

    The characteristics and design of a high-bandwidth flow sensor that uses an AC glow discharge (plasma) as the sensing element is presented. The plasma forms in the air gap between two protruding low profile electrodes attached to a probe body. The output from the anemometer is an amplitude modulated version of the AC voltage input that contains information about the mean and fluctuating velocity components. The anemometer circuitry includes resistance and capacitance elements that simulate a dielectric-barrier to maintain a diffuse plasma, and a constant-current feedback control that maintains operation within the desired glow discharge regime over an extended range of air velocities. Mean velocity calibrations are demonstrated over a range from 0 to 140 m s-1. Over this velocity range, the mean output voltage varied linearly with air velocity, providing a constant static sensitivity. The effect of the electrode gap and input AC carrier frequency on the anemometer static sensitivity and dynamic response are investigated. Experiments are performed to compare measurements obtained with a plasma sensor operating at two AC carrier frequencies against that of a constant-temperature hot-wire. All three sensors were calibrated against the same known velocity reference. An uncertainty based on the standard deviation of the velocity calibration fit was applied to the mean and fluctuating velocity measurements of the three sensors. The motivation is not to replace hot-wires as a general measurement tool, but rather as an alternative to hot-wires in harsh environments or at high Mach numbers where they either have difficulty in surviving or lack the necessary frequency response.

  17. THE ACS NEARBY GALAXY SURVEY TREASURY

    SciTech Connect

    Dalcanton, Julianne J.; Williams, Benjamin F.; Rosema, Keith; Gogarten, Stephanie M.; Christensen, Charlotte; Gilbert, Karoline; Hodge, Paul; Seth, Anil C.; Dolphin, Andrew; Holtzman, Jon; Skillman, Evan D.; Weisz, Daniel; Cole, Andrew; Girardi, Leo; Karachentsev, Igor D.; Olsen, Knut; Freeman, Ken; Gallart, Carme; De Jong, Roelof S. E-mail: ben@astro.washington.edu E-mail: stephanie@astro.washington.edu E-mail: fabio@astro.washington.edu E-mail: aseth@cfa.harvard.edu

    2009-07-15

    The ACS Nearby Galaxy Survey Treasury (ANGST) is a systematic survey to establish a legacy of uniform multi-color photometry of resolved stars for a volume-limited sample of nearby galaxies (D < 4 Mpc). The survey volume encompasses 69 galaxies in diverse environments, including close pairs, small and large groups, filaments, and truly isolated regions. The galaxies include a nearly complete range of morphological types spanning a factor of {approx}10{sup 4} in luminosity and star formation rate. The survey data consist of images taken with the Advanced Camera for Surveys (ACS) on the Hubble Space Telescope (HST), supplemented with archival data and new Wide Field Planetary Camera 2 (WFPC2) imaging taken after the failure of ACS. Survey images include wide field tilings covering the full radial extent of each galaxy, and single deep pointings in uncrowded regions of the most massive galaxies in the volume. The new wide field imaging in ANGST reaches median 50% completenesses of m {sub F475W} = 28.0 mag, m {sub F606W} = 27.3 mag, and m {sub F814W} = 27.3 mag, several magnitudes below the tip of the red giant branch (TRGB). The deep fields reach magnitudes sufficient to fully resolve the structure in the red clump. The resulting photometric catalogs are publicly accessible and contain over 34 million photometric measurements of >14 million stars. In this paper we present the details of the sample selection, imaging, data reduction, and the resulting photometric catalogs, along with an analysis of the photometric uncertainties (systematic and random), for both ACS and WFPC2 imaging. We also present uniformly derived relative distances measured from the apparent magnitude of the TRGB.

  18. Graphs for Isotopes of 89-Ac (Actinium)

    NASA Astrophysics Data System (ADS)

    Sukhoruchkin, S. I.; Soroko, Z. N.

    This document is part of the Supplement containing the complete sets of data of Subvolume B `Nuclei with Z = 55 - 100' of Volume 22 `Nuclear Binding Energies and Atomic Masses' of Landolt-Börnstein - Group I `Elementary Particles, Nuclei and Atoms', and additionally including data for nuclei with Z = 101 - 130. It provides a graphic representation of nucleon separation energies and residual interaction parameters for isotopes of the chemical element 89-Ac (Actinium, atomic number Z = 89).

  19. The ACS Nearby Galaxy Survey Treasury

    NASA Astrophysics Data System (ADS)

    Dalcanton, Julianne J.; Williams, Benjamin F.; Seth, Anil C.; Dolphin, Andrew; Holtzman, Jon; Rosema, Keith; Skillman, Evan D.; Cole, Andrew; Girardi, Léo; Gogarten, Stephanie M.; Karachentsev, Igor D.; Olsen, Knut; Weisz, Daniel; Christensen, Charlotte; Freeman, Ken; Gilbert, Karoline; Gallart, Carme; Harris, Jason; Hodge, Paul; de Jong, Roelof S.; Karachentseva, Valentina; Mateo, Mario; Stetson, Peter B.; Tavarez, Maritza; Zaritsky, Dennis; Governato, Fabio; Quinn, Thomas

    2009-07-01

    The ACS Nearby Galaxy Survey Treasury (ANGST) is a systematic survey to establish a legacy of uniform multi-color photometry of resolved stars for a volume-limited sample of nearby galaxies (D < 4 Mpc). The survey volume encompasses 69 galaxies in diverse environments, including close pairs, small and large groups, filaments, and truly isolated regions. The galaxies include a nearly complete range of morphological types spanning a factor of ~104 in luminosity and star formation rate. The survey data consist of images taken with the Advanced Camera for Surveys (ACS) on the Hubble Space Telescope (HST), supplemented with archival data and new Wide Field Planetary Camera 2 (WFPC2) imaging taken after the failure of ACS. Survey images include wide field tilings covering the full radial extent of each galaxy, and single deep pointings in uncrowded regions of the most massive galaxies in the volume. The new wide field imaging in ANGST reaches median 50% completenesses of m F475W = 28.0 mag, m F606W = 27.3 mag, and m F814W = 27.3 mag, several magnitudes below the tip of the red giant branch (TRGB). The deep fields reach magnitudes sufficient to fully resolve the structure in the red clump. The resulting photometric catalogs are publicly accessible and contain over 34 million photometric measurements of >14 million stars. In this paper we present the details of the sample selection, imaging, data reduction, and the resulting photometric catalogs, along with an analysis of the photometric uncertainties (systematic and random), for both ACS and WFPC2 imaging. We also present uniformly derived relative distances measured from the apparent magnitude of the TRGB.

  20. Level structure and reflection asymmetric shape in sup 223 Ac

    SciTech Connect

    Sheline, R.K.; Liang, C.F.; Paris, P. )

    1990-07-20

    Mass separated sources of {sup 227}Pa (separated as PaF{sub 4}{sup +} ions) were used to study the level structure of {sup 223}Ac following alpha decay. The levels in {sup 223}Ac are interpreted as K = 5/2{sup {plus minus}} parity doublet bands which occur naturally in reflection asymmetric models and the multiphonon octupole model. The anomalous structure of the K = 3/2{sup {minus}} band is explained in terms of Coriolis coupling. The low lying parity doublet bands in {sup 223}Ac, {sup 225}Ac, and {sup 227}Ac are compared and contrasted.

  1. Channel model for AC electric arc

    NASA Astrophysics Data System (ADS)

    Larsen, H. L.

    1993-06-01

    This report contains the results from calculations of free-burning AC electric arcs in argon. In order to calculate the arc current and arc voltage, the external electric circuit must be taken into consideration. The external circuit is modeled by an equivalent circuit consisting of an ideal AC voltage source, a loss resistance, and an inductance. The qualitative behavior of the current-voltage characteristic is in agreement with observed characteristics, but experimental data are necessary in order to check whether the calculated power loss is reasonable. Non-symmetry was modeled by introducing different anode and cathode falls in the two half periods. An attempt at taking into account different cathode current densities in the two half periods, depending on whether the electrode or silicon melt is cathode, did not give satisfactory results. Thermionic emission was assumed in both half periods, but this may not be the right mechanism when the silicon melt is cathode. The time delay of the AC arc compared to the DC case is modeled by a time constant. It was shown that this preset time constant must be in agreement with the mean 'mechanical' relaxation time in the arc in order to fulfill the energy balance. By updating the time constant until this is achieved, the time constant is eliminated as a parameter that must be chosen a priori.

  2. The ACS Nearby Galaxy Survey Treasury

    NASA Astrophysics Data System (ADS)

    Weisz, Daniel R.

    2010-01-01

    The ACS Nearby Galaxy Survey Treasury (ANGST) is a systematic survey to establish a legacy of uniform multi-color photometry of resolved stars for a volume-limited sample of nearby galaxies (D<4Mpc). The survey volume encompasses 69 galaxies in diverse environments, including close pairs, small & large groups, filaments, and truly isolated regions. The galaxies include a nearly complete range of morphological types spanning a factor of 104 in luminosity and star formation rate. The survey data consists of images taken with the Advanced Camera for Surveys (ACS) on the Hubble Space Telescope, supplemented with archival data and new Wide Field Planetary Camera (WFPC2) imaging taken after the failure of ACS. Survey images include wide field tilings covering the full radial extent of each galaxy, and single deep pointings in uncrowded regions of the most massive galaxies in the volume. We will discuss the many ways in which this data set is being used to reconstruct the star formation history of galaxies within the local volume.

  3. Vocational Support Approaches in Autism Spectrum Disorder: A Synthesis Review of the Literature

    ERIC Educational Resources Information Center

    Nicholas, David B.; Attridge, Mark; Zwaigenbaum, Lonnie; Clarke, Margaret

    2015-01-01

    This synthesis-based analysis identifies and reviews studies evaluating vocational resources for adults with autism spectrum disorder. It is based on a larger systematic review of intervention studies in autism spectrum disorder, from which a critical interpretive synthesis was conducted on studies related to vocation and autism spectrum disorder.…

  4. 77 FR 18793 - Spectrum Sharing Innovation Test-Bed Pilot Program

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-03-28

    ... National Telecommunications and Information Administration Spectrum Sharing Innovation Test-Bed Pilot... conduct in Phase II/III of the Spectrum Sharing Innovation Test-Bed pilot program to assess whether... Communications Commission (FCC) and other federal agencies, established a Spectrum Sharing Innovation...

  5. Electrical Conductivity and Dielectrical Properties of Bulk Methylene Green

    NASA Astrophysics Data System (ADS)

    El-Menyawy, E. M.; Zedan, I. T.; Mansour, A. M.

    2017-03-01

    Thermal stability, direct current electrical conductivity (σ DC), alternating current electrical conductivityAC) and dielectric properties of bulk methylene green (MG) have been investigated. The thermal stability of MG was studied by differential scanning calorimetry and thermogravimetry techniques. Temperature dependence of σ DC showed that the MG has semiconductor behavior with two activation energies determined as 0.12 eV and 0.31 eV in the temperature range 303-343 K and 363-463 K, respectively. The σ AC of bulk MG was performed in the frequency range 150 Hz-5 MHz and temperature range 303-463 K. The dependence of AC conductivity on frequency for MG is found to satisfy Jonscher's universal power law, especially at high frequencies. The correlated barrier hopping model is found to be applicable in which the density of localized states is determined. The σ AC is thermally activated and the activation energy decreases with the increases in frequency. The variation of the real and imaginary parts of the dielectric constant with the frequency and temperature is explained.

  6. Energy transfer in strained graphene assisted by discrete breathers excited by external ac driving

    NASA Astrophysics Data System (ADS)

    Evazzade, Iman; Lobzenko, Ivan P.; Korznikova, Elena A.; Ovid'ko, Ilya A.; Roknabadi, Mahmood Rezaee; Dmitriev, Sergey V.

    2017-01-01

    In the present molecular-dynamics study, external ac driving is used at frequencies outside the phonon spectrum to excite gap DBs in uniformly strained graphene nanoribbon. Harmonic displacement or harmonic force is applied to a zigzag atomic chain of graphene. In the former case, nonpropagating DBs are excited on the atoms next to the driven atoms, while in the latter case the excited DBs propagate along the nanoribbon. The energy transfer along the nanoribbon assisted by the DBs is investigated in detail, and the differences between harmonic displacement driving and harmonic force driving are discussed. It is concluded that the amplitude of external driving at out-of-phonon spectrum frequencies should not necessarily be large to obtain a noticeable energy transfer to the system. Overall, our results suggest that external harmonic driving even at relatively small driving amplitudes can be used to control excitation of DBs and consequently the energy transfer to the system.

  7. Total AC losses in twisted and untwisted multifilamentary Bi-2223 superconducting tapes carrying AC transport current in AC longitudinal magnetic field

    NASA Astrophysics Data System (ADS)

    Amemiya, Naoyuki; Jin, Feng; Jiang, Zhenan; Shirai, Shunsuke; ten Haken, Bennie; Rabbers, Jan-Jaap; Ayai, Naoki; Hayashi, Kazuhiko

    2003-03-01

    In some electrical apparatuses, superconducting tapes are exposed to the longitudinal magnetic field. In this work, AC losses were measured in twisted and untwisted Bi-2223 tapes carrying AC transport current in the AC longitudinal magnetic field. In twisted tapes, the transport, magnetization and total losses depend on the relative direction of the longitudinal magnetic field to the direction of the transport current, while the field direction does not influence the AC loss characteristics in untwisted tapes. In the Z-twisted tapes, the total AC loss is larger in the longitudinal magnetic field that is anti-parallel to the transport current than in the longitudinal magnetic field of another direction. Numerical analysis shows that this field direction dependence of the total AC loss results from the change in the current distribution. In the longitudinal magnetic field that is anti-parallel to the transport current, the total AC loss in the Z-twisted tape is more than that in the untwisted tape. This dependence on the field direction is reversed in S-twisted tapes. It is to be noted that the twist increases the total AC loss in a longitudinal magnetic field of a certain direction, while it reduces the AC loss in the transverse magnetic field.

  8. AC loss measurements of twisted and untwisted BSCCO multifilamentary tapes

    NASA Astrophysics Data System (ADS)

    Jiang, Zhenan; Amemiya, Naoyuki; Nishioka, Takamasa; Oh, Sang-Soo

    2005-01-01

    AC losses in twisted and untwisted BSCCO multifilamentary superconducting tapes with Ag matrix developed in DAPAS program were measured by an electrical method. Magnetization and transport losses were measured by a pick-up coil and by a voltage taps. Total AC loss during simultaneous application of AC transport current and an AC transverse magnetic field was given by the sum of the magnetization and transport losses measured during this simultaneous application. The magnetization loss without transport current of untwisted and twisted tapes was measured first to evaluate the effect of twisting to decouple filaments. Then, the total AC loss of the twisted tape was measured in transverse magnetic fields with various amplitudes and orientations, while the amplitude of the transport current was fixed. The measured total AC loss in a parallel transverse magnetic field was compared with some theoretical models to study the detailed characteristics of the measured total AC loss of the sample.

  9. Development of a hardware-based AC microgrid for AC stability assessment

    NASA Astrophysics Data System (ADS)

    Swanson, Robert R.

    As more power electronic-based devices enable the development of high-bandwidth AC microgrids, the topic of microgrid power distribution stability has become of increased interest. Recently, researchers have proposed a relatively straightforward method to assess the stability of AC systems based upon the time-constants of sources, the net bus capacitance, and the rate limits of sources. In this research, a focus has been to develop a hardware test system to evaluate AC system stability. As a first step, a time domain model of a two converter microgrid was established in which a three phase inverter acts as a power source and an active rectifier serves as an adjustable constant power AC load. The constant power load can be utilized to create rapid power flow transients to the generating system. As a second step, the inverter and active rectifier were designed using a Smart Power Module IGBT for switching and an embedded microcontroller as a processor for algorithm implementation. The inverter and active rectifier were designed to operate simultaneously using a synchronization signal to ensure each respective local controller operates in a common reference frame. Finally, the physical system was created and initial testing performed to validate the hardware functionality as a variable amplitude and variable frequency AC system.

  10. The Hubble Legacy Archive ACS grism data

    NASA Astrophysics Data System (ADS)

    Kümmel, M.; Rosati, P.; Fosbury, R.; Haase, J.; Hook, R. N.; Kuntschner, H.; Lombardi, M.; Micol, A.; Nilsson, K. K.; Stoehr, F.; Walsh, J. R.

    2011-06-01

    A public release of slitless spectra, obtained with ACS/WFC and the G800L grism, is presented. Spectra were automatically extracted in a uniform way from 153 archival fields (or "associations") distributed across the two Galactic caps, covering all observations to 2008. The ACS G800L grism provides a wavelength range of 0.55-1.00 μm, with a dispersion of 40 Å/pixel and a resolution of ~80 Å for point-like sources. The ACS G800L images and matched direct images were reduced with an automatic pipeline that handles all steps from archive retrieval, alignment and astrometric calibration, direct image combination, catalogue generation, spectral extraction and collection of metadata. The large number of extracted spectra (73,581) demanded automatic methods for quality control and an automated classification algorithm was trained on the visual inspection of several thousand spectra. The final sample of quality controlled spectra includes 47 919 datasets (65% of the total number of extracted spectra) for 32 149 unique objects, with a median iAB-band magnitude of 23.7, reaching 26.5 AB for the faintest objects. Each released dataset contains science-ready 1D and 2D spectra, as well as multi-band image cutouts of corresponding sources and a useful preview page summarising the direct and slitless data, astrometric and photometric parameters. This release is part of the continuing effort to enhance the content of the Hubble Legacy Archive (HLA) with highly processed data products which significantly facilitate the scientific exploitation of the Hubble data. In order to characterize the slitless spectra, emission-line flux and equivalent width sensitivity of the ACS data were compared with public ground-based spectra in the GOODS-South field. An example list of emission line galaxies with two or more identified lines is also included, covering the redshift range 0.2 - 4.6. Almost all redshift determinations outside of the GOODS fields are new. The scope of science projects

  11. High frequency conductivity of hot electrons in carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Amekpewu, M.; Mensah, S. Y.; Musah, R.; Mensah, N. G.; Abukari, S. S.; Dompreh, K. A.

    2016-05-01

    High frequency conductivity of hot electrons in undoped single walled achiral Carbon Nanotubes (CNTs) under the influence of ac-dc driven fields was considered. We investigated semi-classically Boltzmann's transport equation with and without the presence of the hot electrons' source by deriving the current densities in CNTs. Plots of the normalized current density versus frequency of ac-field revealed an increase in both the minimum and maximum peaks of normalized current density at lower frequencies as a result of a strong injection of hot electrons. The applied ac-field plays a twofold role of suppressing the space-charge instability in CNTs and simultaneously pumping an energy for lower frequency generation and amplification of THz radiations. These have enormous promising applications in very different areas of science and technology.

  12. Temperature and frequency dependent conductivity of lithium doped bismuth zinc vanadate semiconducting glassy system

    NASA Astrophysics Data System (ADS)

    Dahiya, S.; Punia, R.; Murugavel, S.; Maan, A. S.

    2014-11-01

    The ac conductivity of bismuth zinc vanadate glasses of compositions x Li2O (100 - x) (50V2O5·20 Bi2O3·30 ZnO); x = 0, 2, 4, 6, and 8 has been studied in the frequency range 10-1 Hzb-2 MHz and in temperature range 313-533 K. The temperature and frequency dependent conductivity is found to obey Almond-West universal power law for all the studied lithium doped bismuth zinc vanadate glassy systems. Various parameters such as dc conductivity ( σ dc ), crossover frequency ( ω H ) and frequency exponent ( s) have been estimated by fitting the experimental data of ac conductivity to Almond-West universal power law. It has been observed that the ac conductivity of bismuth zinc vanadate glass system decreases with the increase in Li2O content. The ac conductivity and its frequency exponent have been analyzed in the frame work of various theoretical models. The ac conduction seems to take place via tunneling of overlapping large polarons in all the compositions.

  13. Hybrid spread spectrum radio system

    DOEpatents

    Smith, Stephen F [London, TN; Dress, William B [Camas, WA

    2010-02-09

    Systems and methods are described for hybrid spread spectrum radio systems. A method, includes receiving a hybrid spread spectrum signal including: fast frequency hopping demodulating and direct sequence demodulating a direct sequence spread spectrum signal, wherein multiple frequency hops occur within a single data-bit time and each bit is represented by chip transmissions at multiple frequencies.

  14. Joint Electromagnetic Spectrum Management Operations

    DTIC Science & Technology

    2012-03-20

    synchronizing, and deconflicting JEMSMO actions (p. IV-7) Doctrine Update for JP 6-01, Joint Electromagnetic Spectrum Management Operations...communications system directorate of a joint staff (J-6), to support joint planning, coordination, and control of the spectrum for assigned forces. Executive...in the respective Service or joint publications. Interference Resolution To ensure critical frequencies and spectrum-dependent systems are

  15. Ac conductivity studies of solution combustion synthesized nanocrystalline Li2MgZrO4 material

    NASA Astrophysics Data System (ADS)

    Cheruku, Rajesh; Vijayan, Lakshmi; Govindaraj, G.

    2012-06-01

    A phase-pure nanocrystalline Li2MgZrO4 material is synthesized by solution combustion synthesis. In this study citric acid is used as fuel and pH of the homogenous solution is maintained. The material is crystallized in a cubic rock-salt structure of space group Fm⃞3m. TEM analysis revealed that the material is formed as nano-crystallites. The structural characterization is accomplished through X-ray diffraction, thermogravimetry, differential thermal analysis, transmission electron microscopy and electrical characterization is done through impedance spectroscopy and the results are reported.

  16. Method and apparatus for generating radiation utilizing DC to AC conversion with a conductive front

    DOEpatents

    Dawson, J.M.; Mori, W.B.; Lai, C.H.; Katsouleas, T.C.

    1998-07-14

    Method and apparatus ar disclosed for generating radiation of high power, variable duration and broad tunability over several orders of magnitude from a laser-ionized gas-filled capacitor array. The method and apparatus convert a DC electric field pattern into a coherent electromagnetic wave train when a relativistic ionization front passes between the capacitor plates. The frequency and duration of the radiation is controlled by the gas pressure and capacitor spacing. 4 figs.

  17. Method and apparatus for generating radiation utilizing DC to AC conversion with a conductive front

    DOEpatents

    Dawson, John M.; Mori, Warren B.; Lai, Chih-Hsiang; Katsouleas, Thomas C.

    1998-01-01

    Method and apparatus for generating radiation of high power, variable duration and broad tunability over several orders of magnitude from a laser-ionized gas-filled capacitor array. The method and apparatus convert a DC electric field pattern into a coherent electromagnetic wave train when a relativistic ionization front passes between the capacitor plates. The frequency and duration of the radiation is controlled by the gas pressure and capacitor spacing.

  18. Cross-resistance and interactions between Bt toxins Cry1Ac and Cry2Ab against the cotton bollworm.

    PubMed

    Wei, Jizhen; Guo, Yuyuan; Liang, Gemei; Wu, Kongming; Zhang, Jie; Tabashnik, Bruce E; Li, Xianchun

    2015-01-14

    To delay evolution of pest resistance to transgenic crops producing insecticidal proteins from Bacillus thuringiensis (Bt), the "pyramid" strategy uses plants that produce two or more toxins that kill the same pest. We conducted laboratory diet experiments with the cotton bollworm, Helicoverpa armigera, to evaluate cross-resistance and interactions between two toxins in pyramided Bt cotton (Cry1Ac and Cry2Ab). Selection with Cry1Ac for 125 generations produced 1000-fold resistance to Cry1Ac and 6.8-fold cross-resistance to Cry2Ab. Selection with Cry2Ab for 29 generations caused 5.6-fold resistance to Cry2Ab and 61-fold cross-resistance to Cry1Ac. Without exposure to Bt toxins, resistance to both toxins decreased. For each of the four resistant strains examined, 67 to 100% of the combinations of Cry1Ac and Cry2Ab tested yielded higher than expected mortality, reflecting synergism between these two toxins. Results showing minor cross-resistance to Cry2Ab caused by selection with Cry1Ac and synergism between these two toxins against resistant insects suggest that plants producing both toxins could prolong the efficacy of Bt cotton against this pest in China. Including toxins against which no cross-resistance occurs and integrating Bt cotton with other control tactics could also increase the sustainability of management strategies.

  19. Cross-resistance and interactions between Bt toxins Cry1Ac and Cry2Ab against the cotton bollworm

    PubMed Central

    Wei, Jizhen; Guo, Yuyuan; Liang, Gemei; Wu, Kongming; Zhang, Jie; Tabashnik, Bruce E.; Li, Xianchun

    2015-01-01

    To delay evolution of pest resistance to transgenic crops producing insecticidal proteins from Bacillus thuringiensis (Bt), the "pyramid" strategy uses plants that produce two or more toxins that kill the same pest. We conducted laboratory diet experiments with the cotton bollworm, Helicoverpa armigera, to evaluate cross-resistance and interactions between two toxins in pyramided Bt cotton (Cry1Ac and Cry2Ab). Selection with Cry1Ac for 125 generations produced 1000-fold resistance to Cry1Ac and 6.8-fold cross-resistance to Cry2Ab. Selection with Cry2Ab for 29 generations caused 5.6-fold resistance to Cry2Ab and 61-fold cross-resistance to Cry1Ac. Without exposure to Bt toxins, resistance to both toxins decreased. For each of the four resistant strains examined, 67 to 100% of the combinations of Cry1Ac and Cry2Ab tested yielded higher than expected mortality, reflecting synergism between these two toxins. Results showing minor cross-resistance to Cry2Ab caused by selection with Cry1Ac and synergism between these two toxins against resistant insects suggest that plants producing both toxins could prolong the efficacy of Bt cotton against this pest in China. Including toxins against which no cross-resistance occurs and integrating Bt cotton with other control tactics could also increase the sustainability of management strategies. PMID:25586723

  20. Deletion of the AcMNPV core gene ac109 results in budded virions that are non-infectious

    SciTech Connect

    Fang Minggang; Nie, Yingchao; Theilmann, David A.

    2009-06-20

    Autographa californica multiple nucleopolyhedrovirus (AcMNPV) ac109 is a core gene and its function in the virus life cycle is unknown. To determine its role in the baculovirus life cycle, we used the AcMNPV bacmid system to generate an ac109 deletion virus (vAc{sup 109KO}). Fluorescence and light microscopy showed that transfection of vAc{sup 109KO} results in a single-cell infection phenotype. Viral DNA replication is unaffected and the development of occlusion bodies in vAc{sup 109KO}-transfected cells evidenced progression to the very late phases of viral infection. Western blot and confocal immunofluorescence analysis showed that AC109 is expressed in the cytoplasm and nucleus throughout infection. In addition, AC109 is a structural protein as it was detected in both budded virus (BV) and occlusion derived virus in both the envelope and nucleocapsid fractions. Titration assays by qPCR and TCID{sub 50} showed that vAc{sup 109KO} produced BV but the virions are non-infectious. The vAc{sup 109KO} BV were indistinguishable from the BV of repaired and wild type control viruses as determined by negative staining and electron microscopy.

  1. Probing radiation damage by alternated current conductivity as a method to characterize electron hopping conduction in DNA molecules

    SciTech Connect

    Gomes, Paulo J.; Coelho, Margarida; Antonio Ribeiro, Paulo; Raposo, Maria; Dionisio, Madalena

    2012-09-17

    Analysis of AC electrical conductivity of deoxyribonucleic acid (DNA) thin films, irradiated with ultraviolet (UV) light, revealed that electrical conduction arises from DNA chain electron hopping between base-pairs and phosphate groups. The hopping distance calculated from correlated barrier hopping model equals the distance between DNA base-pairs, which is consistent with the loss of conductivity with irradiation time arising from a decrease in phosphates groups. In the high frequency regime, at a given frequency, real part of conductivity strongly depends on irradiation time particularly for low dose levels suggesting the use of DNA based films for UV radiation sensors.

  2. Spectroscopic Observations and Analysis of the Unusual Type Ia SN1999ac

    SciTech Connect

    Garavini, G.; Aldering, G.; Amadon, A.; Amanullah, R.; Astier,P.; Balland, C.; Blanc, G.; Conley, A.; Dahlen, T.; Deustua, S.E.; Ellis,R.; Fabbro, S.; Fadeyev, V.; Fan, X.; Folatelli, G.; Frye, B.; Gates,E.L.; Gibbons, R.; Goldhaber, G.; Goldman, B.; Goobar, A.; Groom, D.E.; Haissinski, J.; Hardin, D.; Hook, I.; Howell, D.A.; Kent, S.; Kim, A.G.; Knop, R.A.; Kowalski, M.; Kuznetsova, N.; Lee, B.C.; Lidman, C.; Mendez,J.; Miller, G.J.; Moniez, M.; Mouchet, M.; Mourao, A.; Newberg, H.; Nobili, S.; Nugent, P.E.; Pain, R.; Perdereau, O.; Perlmutter, S.; Quimby, R.; Regnault, N.; Rich, J.; Richards, G.T.; Ruiz-Lapuente, P.; Schaefer, B.E.; Schahmaneche, K.; Smith, E.; Spadafora, A.L.; Stanishev,V.; Thomas, R.C.; Walton, N.A.; Wang, L.; Wood-Vasey, W.M.

    2005-07-12

    The authors present optical spectra of the peculiar Type Ia supernova (SN Ia) 1999ac. The data extend from -15 to +42 days with respect to B-band maximum and reveal an event that is unusual in several respects. prior to B-band maximum, the spectra resemble those of SN 1999aa, a slowly declining event, but possess stronger Si II and Ca II signatures (more characteristic of a spectroscopically normal SN). Spectra after B-band maximum appear more normal. The expansion velocities inferred from the Iron lines appear to be lower than average; whereas, the expansion velocity inferred from Calcium H and K are higher than average. The expansion velocities inferred from the Iron lines appear to be lower than average; whereas, the expansion velocity inferred from Calcium H and K are higher than average. The expansion velocities inferred from Si II are among the slowest ever observed, though SN 1999ac is not particularly dim. The analysis of the parameters v{sub 10}(Si II), R(Si II), v, and {Delta}m{sub 15} further underlines the unique characteristics of SN 1999ac. They find convincing evidence of C II {lambda}6580 in the day -15 spectrum with ejection velocity v > 16,000 km s{sup -1}, but this signature disappears by day -9. This rapid evolution at early times highlights the importance of extremely early-time spectroscopy.

  3. Transport conductivity of graphene at RF and microwave frequencies

    NASA Astrophysics Data System (ADS)

    Awan, S. A.; Lombardo, A.; Colli, A.; Privitera, G.; Kulmala, T. S.; Kivioja, J. M.; Koshino, M.; Ferrari, A. C.

    2016-03-01

    We measure graphene coplanar waveguides from direct current (DC) to a frequency f = 13.5 GHz and show that the apparent resistance (in the presence of parasitic impedances) has an {ω }2 dependence (where ω =2π f), but the intrinsic conductivity (without the influence of parasitic impedances) is frequency-independent. Consequently, in our devices the real part of the complex alternating current (AC) conductivity is the same as the DC value and the imaginary part is ˜0. The graphene channel is modeled as a parallel resistive-capacitive network with a frequency dependence identical to that of the Drude conductivity with momentum relaxation time ˜2.1 ps, highlighting the influence of AC electron transport on the electromagnetic properties of graphene. This can lead to optimized design of high-speed analog field-effect transistors, mixers, frequency doublers, low-noise amplifiers and radiation detectors.

  4. Hall conductance in graphene with point defects.

    PubMed

    İslamoğlu, S; Oktel, M Ö; Gülseren, O

    2013-02-06

    We investigate the Hall conductance of graphene with point defects within the Kubo formalism, which allows us to calculate the Hall conductance without constraining the Fermi energy to lie in a gap. For pure graphene, which we model using a tight-binding Hamiltonian, we recover both the usual and the anomalous integer quantum Hall effects depending on the proximity to the Dirac points. We investigate the effect of point defects on Hall conduction by considering a dilute but regular array of point defects incorporated into the graphene lattice. We extend our calculations to include next nearest neighbor hopping, which breaks the bipartite symmetry of the lattice. We find that impurity atoms which are weakly coupled to the rest of the lattice result in gradual disappearance of the high conductance value plateaus. For such impurities, especially for vacancies which are decoupled from the lattice, strong modification of the Hall conductance occurs near the E = 0 eV line, as impurity states are highly localized. In contrast, if the impurities are strongly coupled, they create additional Hall conductance plateaus at the extremum values of the spectrum, signifying separate impurity bands. Hall conductance values within the original spectrum are not strongly modified.

  5. Conducting compositions of matter

    NASA Technical Reports Server (NTRS)

    Viswanathan, Tito (Inventor)

    2000-01-01

    The invention provides conductive compositions of matter, as well as methods for the preparation of the conductive compositions of matter, solutions comprising the conductive compositions of matter, and methods of preparing fibers or fabrics having improved anti-static properties employing the conductive compositions of matter.

  6. Conducting Compositions of Matter

    NASA Technical Reports Server (NTRS)

    Viswanathan, Tito (Inventor)

    1999-01-01

    The invention provides conductive compositions of matter, as well as methods for the preparation of the conductive compositions of matter, solutions comprising the conductive compositions of matter, and methods of preparing fibers or fabrics having improved anti-static properties employing the conductive compositions of matter.

  7. Polyaniline Based Conductive Textiles

    NASA Astrophysics Data System (ADS)

    Teli, M.; Dash, S.; Desai, P.

    2014-12-01

    The conductive polymers were mixed with binder and coated on cotton, polyester and wool fabric, keeping conductive polymer concentration at 5 %. Conductive woven fabrics were obtained by pad-dry-cure coating technique. The surface and bulk conductivity behaviour of the coating paste with respect to temperature were studied using four probe and two probe technique. The conductivity studies show that the coated fabrics have good electrical conductivity in the range of 33.2 μS/cm-3281 μS/cm and there was an increase in conductivity with rise in temperature.

  8. Scaling of velocity and scalar structure functions in ac electrokinetic turbulence

    NASA Astrophysics Data System (ADS)

    Zhao, Wei; Wang, Guiren

    2017-02-01

    Electrokinetic (EK) turbulence or electrohydrodynamic (EHD) turbulence has been recently achieved in different fluids under both ac [G. Wang et al., Lab Chip 14, 1452 (2014), 10.1039/C3LC51403J; Phys. Rev. E 93, 013106 (2016), 10.1103/PhysRevE.93.013106] and dc electric fields [A. Varshney et al., Soft Matter 12, 1759 (2016), 10.1039/C5SM02316E]. Here, through dimensional analysis, scaling laws of both velocity and electric conductivity structure functions in the forced cascade region of ac EK turbulence can be predicated (similar to Bolgiano-Obukhov scaling law in turbulent Rayleigh-Bénard convection), in either macroscale or microscale flows. In the forced cascade region, EK force, which relies on the direct cascade of conductivity structures, injects energy directly into a wide spectral region to sustain the flow disturbance. The scaling exponents of the second-order velocity and conductivity structures are 2/5 and 4/5, respectively. In addition to the scaling regions, two characteristic small length scales are derived for both weak and strong electric body forces, respectively. This theoretical investigation can significantly enhance our understanding of EK or EHD turbulence while forced by an ac electric field. It can further broaden our understanding of the forced cascade region of forced turbulence and make the manipulation of the turbulent cascade process more flexible and controllable.

  9. ac-Field-induced fluid pumping in microsystems with asymmetric temperature gradients.

    PubMed

    Holtappels, Moritz; Stubbe, Marco; Gimsa, Jan

    2009-02-01

    We present two different designs of electrohydrodynamic micropumps for microfluidic systems. The micropumps have no movable parts, and their simple design allows for fabrication by microsystems technology. The pumps are operated by ac voltages from 1 to 60 V and were tested with aqueous solutions in the conductivity range of 1-112 mS m(-1). The pump effect is induced by an ac electric field across a fluid medium with an inhomogeneous temperature distribution. It is constant over a wide range of the ac field frequency with a conductivity-dependent drop-off at high frequencies. The temperature-dependent conductivity and permittivity distributions in the fluid induce space charges that interact with the electric field and induce fluid motion. The temperature distribution can be generated either by Joule heating in the medium or by external heating. We present experimental results obtained with two prototypes featuring Joule heating and external heating by a heating filament. Experimental and numerical results are compared with an analytical model.

  10. AC field induced-charge electroosmosis over leaky dielectric blocks embedded in a microchannel.

    PubMed

    Zhao, Cunlu; Yang, Chun

    2011-02-01

    An effective electrical boundary condition is formulated to describe AC field-driven induced-charge electrokinetic (ICEK) phenomena at the interface between a liquid and a leaky dielectric solid. Since most materials in reality possess finite dielectric and conductive properties, i.e. leaky dielectric, the present boundary condition can be used to describe the induced zeta potential on a leaky dielectric surface with consideration of both bond charges (due to polarization) and free charges (due to conduction). Two well-known limiting cases, i.e. the perfectly dielectric and the perfectly conducting wall boundary conditions can be recovered from the present formulation. Utilizing the derived boundary condition, we obtain analytical solutions in closed form for the AC field-driven induced-charge electroosmosis (ICEO) over two symmetric leaky dielectric blocks embedded in the walls of an infinitely long microchannel. Two important factors for the induced zeta potential are identified to respectively account for the polarization charges and the free charges, and their effects on AC field-driven ICEO oscillating flow patterns are analyzed. It is found that the flow patterns exhibit two counter-rotating vortices, which can be deformed, relocated, eliminated and even reverse their rotating directions. It is very promising that such temporary evolution of flow patterns can possibly induce chaotic advection which can enhance microfluidic mixing.

  11. Conduction mechanism in bismuth silicate glasses containing titanium

    NASA Astrophysics Data System (ADS)

    Dult, Meenakshi; Kundu, R. S.; Murugavel, S.; Punia, R.; Kishore, N.

    2014-11-01

    Bismuth silicate glasses mixed with different concentrations of titanium dioxide having compositions xTiO2-(60-x)Bi2O3-40SiO2 with x=0, 5, 10, 15 and 20 were prepared by the normal melt quench technique. The frequency dependence of the ac electrical conductivity of different compositions of titanium bismuth silicate glasses has been studied in the frequency range 10-1 Hz to 10 MHz and in the temperature range 623-703 K. The temperature and frequency dependent conductivity is found to obey Jonscher's universal power law for all the compositions of titanium bismuth silicate glass system. The dc conductivity (σdc), so called crossover frequency (ωH), and frequency exponent (s) have been estimated from the fitting of experimental data of ac conductivity with Jonscher's universal power law. Enthalpy to dissociate the cation from its original site next to a charge compensating center (Hf) and enthalpy of migration (Hm) have also been estimated. The conductivity data have been analyzed in terms of different theoretical models to determine the possible conduction mechanism. Analysis of the conductivity data and the frequency exponent shows that the correlated barrier hopping of electrons between Ti3+ and Ti4+ ions in the glasses is the most favorable mechanism for ac conduction. The temperature dependent dc conductivity has been analyzed in the framework of theoretical variable range hopping model (VRH) proposed by Mott which describe the hopping conduction in disordered semiconducting systems. The various polaron hopping parameters have also been deduced. Mott's VRH model is found to be in good agreement with experimental data and the values of inverse localization length of s-like wave function (α) obtained by this model with modifications suggested by Punia et al. are close to the ones reported for a number of oxide glasses.

  12. Parameters characterization and optimization of activated carbon (AC) cathodes for microbial fuel cell application.

    PubMed

    Santoro, Carlo; Artyushkova, Kateryna; Babanova, Sofia; Atanassov, Plamen; Ieropoulos, Ioannis; Grattieri, Matteo; Cristiani, Pierangela; Trasatti, Stefano; Li, Baikun; Schuler, Andrew J

    2014-07-01

    Activated carbon (AC) is employed as a cost-effective catalyst for cathodic oxygen reduction in microbial fuel cells (MFC). The fabrication protocols of AC-based cathodes are conducted at different applied pressures (175-3500 psi) and treatment temperatures (25-343°C). The effects of those parameters along with changes in the surface morphology and chemistry on the cathode performances are comprehensively examined. The cathodes are tested in a three-electrode setup and explored in single chamber membraneless MFCs (SCMFCs). The results show that the best performance of the AC-based cathode is achieved when a pressure of 1400 psi is applied followed by heat treatment of 150-200°C for 1h. The influence of the applied pressure and the temperature of the heat treatment on the electrodes and SCMFCs is demonstrated as the result of the variation in the transfer resistance, the surface morphology and surface chemistry of the AC-based cathodes tested.

  13. Comparative study of evaporation using DC and AC filament electron guns

    NASA Astrophysics Data System (ADS)

    Lahiri, Sutanwi; Sahu, G. K.; Baruah, S.; Jana, B.; Dixit, A. R.; Bhardwaj, R. L.; Das, R. C.; Kalra, R.; Kaushik, V.; Majumder, A.; Mohapatra, S.; Dikshit, B.; Mishra, K. K.; Bhatia, M. S.; Bapat, A. V.; Mago, V. K.; Thakur, K. B.; Das, A. K.; Gantayet, L. M.

    2012-11-01

    Electron beam assisted physical vapour deposition (EB-PVD) and purification of metal by repeated melting using electron guns is a well-established technique in industrial metallurgy. Strip electron gun is considered a cost effective alternative to multiple pencil guns for handling of large size substrates. In the electron guns, the thermionic emission of the electrons from a filament is achieved by using AC or DC filament heating. A study of their relative merits and demerits was conducted for the both types of electron guns. Due to finite length of the filament, the magnetic field generated around the filament by heating current drops down towards ends. The DC filament heating results in electron beam with a comet shape having high power density hot spot at one end with low power density tails. With AC filament heating, electron beam oscillates with the frequency as that of heating current. The study of vapour flux distribution using DC gun revealed that highly directional vapour evolution takes place from a smaller hot spot whereas with AC gun vapour evolution occurs from an oscillatory 2D-evaporating source. The vapour deposit on substrate indicated that evaporation using DC gun caused splashing and granular deposit due to volumetric melting and evaporation from the ingot. This is contrary to the AC filament heating wherein quiet evaporation was observed due to surface melting and evaporation. The experimental results are critically reviewed to decide the configuration of electron guns for large-scale evaporation.

  14. Electrically conductive black optical paint

    NASA Technical Reports Server (NTRS)

    Birnbaum, M. M.; Metzler, E. C.; Cleland, E. L.

    1983-01-01

    An electrically conductive flat black paint has been developed for use on the Galileo spacecraft which will orbit Jupiter in the late 1980s. The paint, designed for equipment operating in high-energy radiation fields, has multipurpose functions. Its electrical conductivity keeps differential charging of the spacecraft external surfaces and equipment to a minimum, preventing the buildup of electrostatic fields and arcing. Its flat black aspect minimizes the effects of stray light and unwanted reflectances, when used in optical instruments and on sunshades. Its blackness is suitable, also, for thermal control, when the paint is put on spacecraft surfaces. The paint has good adherence properties, as measured by tape tests, when applied properly to a surface. The electrically conductive paint which was developed has the following characteristics: an electrical resistivity of 5 x 10 to the 7th ohms per square; a visual light total reflectance of approximately 5 percent; an infrared reflectance of 0.13 measured over a spectrum from 10 to the (-5.5) power to 0.001 meter; a solar absorptivity, alpha-s, of 0.93, and a thermal emissivity, epsilon, of 0.87, resulting in an alpha-s/epsilon of 1.07. The formula for making the paint and the process for applying it are described.

  15. The ACS Nearby Galaxy Survey Treasury

    NASA Astrophysics Data System (ADS)

    Dalcanton, Julianne; Williams, B.; Gogarten, S.; Weisz, D.; Skillman, E.; Seth, A.; ANGST Team

    2007-12-01

    The ACS Nearby Galaxy Survey Treasury program (ANGST) is a program to measure photometry for millions of stars in a volume limited sample of 70 nearby galaxies. With this data set, we are deriving spatially resolved star formation histories for both dwarfs and spirals in the local volume. I will highlight initial results from the survey, including ancient star formation histories for massive spirals, halos around dwarf galaxies, spatially-resolved star formation histories in dwarfs and spirals, and the detection of variable stars. I will also discuss the ANGST involved with switching to WFPC2. This program is funded by NASA grant HST GO-10915, administered by STScI.

  16. Nonlinear studies of AC electrokinetic micropumps

    NASA Astrophysics Data System (ADS)

    Bruus, Henrik; Olesen, Laurits H.; Ajdari, Armand

    2006-03-01

    Recent experiments have demonstrated that AC electrokinetic micropumps permit integrable, local, and fast pumping (velocities ˜ mm/s) with low driving voltage of a few volts only. However, they also displayed many quantitative and qualitative discrepancies with existing theories. We therefore extend the latter theories to account for three experimentally relevant effects: (i) vertical confinement of the pumping channel, (ii) Faradaic currents from electrochemical reactions at the electrodes, and (iii) nonlinear surface capacitance of the Debye layer. We report here that these effects indeed affect the pump performance in a way that we can rationalize by physical arguments.

  17. Inverse ac Josephson effect at terahertz frequencies

    NASA Astrophysics Data System (ADS)

    Danchi, W. C.; Golightly, W. J.; Sutton, E. C.

    1989-04-01

    Using the Werthamer (1966) theory of superconducting tunnel junctions, it is shown that zero-crossing ac Josephson steps can occur at frequencies much higher than those expected previously, as long as the voltage waveform is nearly sinusoidal. Limits on the amount of permitted rounding of the Riedel (1964) peak were derived from analytical calculations, and numerical frequency-domain and time-domain computations for realistic junctions were carried out, yielding support for these limits. It is shown that previous arguments that zero-crossing steps could never be observed above the value of half the gap voltage are incorrect, due to the neglect of the Riedel peak.

  18. Mathematical model for the power supply system of an autonomous object with an AC power transmission over a cable rope

    NASA Astrophysics Data System (ADS)

    Rulevskiy, V. M.; Bukreev, V. G.; Shandarova, E. B.; Kuleshova, E. O.; Shandarov, S. M.; Vasilyeva, Yu Z.

    2017-02-01

    A modeling problem of the power system, which provides an AC power transmission to a submersible device over the conducting rope, was considered. The power supply system units and their parameters are described. The system multi-dimensional mathematical model in the variables state space with regard to the nonlinear characteristic of system elements is proposed.

  19. Participation in Daily Activities of Young Adults with High Functioning Autism Spectrum Disorder.

    PubMed

    McCollum, Mary; LaVesser, Patti; Berg, Christine

    2016-03-01

    Young adults with an autism spectrum disorder (ASD) struggle to assume adult roles. This research assessed the feasibility of using the Adolescent and Young Adult Activity Card Sort (AYA-ACS) with emerging adults with high functioning ASD. Two phases were utilized during this research: (1) comparing the activity participation reported by emerging adults with an ASD and that reported by their caring adult; (2) examining the barriers to participation reported. Preliminary results demonstrate that the AYA-ACS appears to be a reliable and valid method of identifying emerging adults' participation strengths as well as personal and environmental challenges in a variety of age-appropriate activities. The AYA-ACS could assist service providers by providing an understanding of the challenges to participation faced by this population and aid in developing client centered interventions.

  20. Resonant AC power system proof-of-concept test program

    NASA Technical Reports Server (NTRS)

    Wappes, Loran J.

    1986-01-01

    Proof-of-concept testing was performed on a 20-kHz, resonant power system breadboard from 1981 through 1985. The testing began with the evaluation of a single, 1.0-kW resonant inverter and progressed to the testing of breadboard systems with higher power levels and more capability. The final breadboard configuration tested was a 25.0-kW breadboard with six inverters providing power to three user-interface modules over a 50-meter, 20-kHz bus. The breadboard demonstrated the ability to synchronize multiple resonant inverters to power a common bus. Single-phase and three-phase 20-kHz power distribution was demonstrated. Simple conversion of 20-kHz to dc and variable-frequency ac was demonstrated as was bidirectional power flow between 20-kHz and dc. Steady state measurements of efficiency, power-factor tolerance, and conducted emissions and conducted susceptibility were made. In addition, transient responses were recorded for such conditions as start up, shut down, load changes. The results showed the 20-kHz resonant system to be a desirable technology for a spacecraft power management and distribution system with multiple users and a utility-type bus.

  1. Sensitivity analysis on an AC600 aluminum skin component

    NASA Astrophysics Data System (ADS)

    Mendiguren, J.; Agirre, J.; Mugarra, E.; Galdos, L.; Saenz de Argandoña, E.

    2016-08-01

    New materials are been introduced on the car body in order to reduce weight and fulfil the international CO2 emission regulations. Among them, the application of aluminum alloys is increasing for skin panels. Even if these alloys are beneficial for the car design, the manufacturing of these components become more complex. In this regard, numerical simulations have become a necessary tool for die designers. There are multiple factors affecting the accuracy of these simulations e.g. hardening, anisotropy, lubrication, elastic behavior. Numerous studies have been conducted in the last years on high strength steels component stamping and on developing new anisotropic models for aluminum cup drawings. However, the impact of the correct modelling on the latest aluminums for the manufacturing of skin panels has been not yet analyzed. In this work, first, the new AC600 aluminum alloy of JLR-Novelis is characterized for anisotropy, kinematic hardening, friction coefficient, elastic behavior. Next, a sensitivity analysis is conducted on the simulation of a U channel (with drawbeads). Then, the numerical an experimental results are correlated in terms of springback and failure. Finally, some conclusions are drawn.

  2. Magnetostrictive materials and method for improving AC characteristics in same

    DOEpatents

    Pulvirenti, Patricia P.; Jiles, David C.

    2001-08-14

    The present invention provides Terfenol-D alloys ("doped" Terfenol) having optimized performances under the condition of time-dependent magnetic fields. In one embodiment, performance is optimized by lowering the conductivity of Terfenol, thereby improving the frequency response. This can be achieved through addition of Group III or IV elements, such as Si and Al. Addition of these types of elements provides scattering sites for conduction electrons, thereby increasing resistivity by 125% which leads to an average increase in penetration depth of 80% at 1 kHz and an increase in energy conversion efficiency of 55%. The permeability of doped Terfenol remains constant over a wider frequency range as compared with undoped Terfenol. These results demonstrate that adding impurities, such as Si and Al, are effective in improving the ac characteristics of Terfenol. A magnetoelastic Gruneisen parameter, .gamma..sub.me, has also been derived from the thermodynamic equations of state, and provides another means by which to characterize the coupling efficiency in magnetostrictive materials on a more fundamental basis.

  3. Temperature and frequency dependent conductivity of bismuth zinc vanadate semiconducting glassy system

    NASA Astrophysics Data System (ADS)

    Punia, R.; Kundu, R. S.; Dult, Meenakshi; Murugavel, S.; Kishore, N.

    2012-10-01

    The ac conductivity of bismuth zinc vanadate glasses with compositions 50V2O5. xBi2O3. (50-x) ZnO has been studied in the frequency range 10-1 Hz to 2 MHz and in temperature range 333.16 K to 533.16 K. The temperature and frequency dependent conductivity is found to obey Jonscher's universal power law for all the compositions of bismuth zinc vanadate glass system. The dc conductivity (σdc), crossover frequency (ωH), and frequency exponent (s) have been estimated from the fitting of experimental data of ac conductivity with Jonscher's universal power law. Enthalpy to dissociate the cation from its original site next to a charge compensating center (Hf) and enthalpy of migration (Hm) have also been estimated. It has been observed that mobility of charge carriers and ac conductivity in case of zinc vanadate glass system increases with increase in Bi2O3 content. In order to determine the conduction mechanism, the ac conductivity and its frequency exponent have been analyzed in the frame work of various theoretical models based on classical hopping over barriers and quantum mechanical tunneling. The ac conduction takes place via tunneling of overlapping large polarons in all the compositions of presently studied vanadate glasses. The fitting of experimental data of ac conductivity with overlapping large polarons tunneling model has also been done. The parameters; density of states at Fermi level (N(EF)), activation energy associated with charge transfer between the overlapping sites (WHO), inverse localization length (α) and polaron radius (rp) obtained from fitting of this model with experimental data are reasonable.

  4. The subjective experience of music in autism spectrum disorder.

    PubMed

    Allen, Rory; Hill, Elisabeth; Heaton, Pamela

    2009-07-01

    Semi-structured interviews were conducted with 12 high-functioning adults on the autism spectrum in order to examine the nature of their personal experiences of music. The analysis showed that most participants exploit music for a wide range of purposes in the cognitive, emotional and social domains, but the autism spectrum disorder (ASD) group's descriptions of mood states reflected a greater reliance on internally focused (arousal) rather than externally focused (emotive) language, when compared with studies of typically developing individuals.

  5. Ac irreversibility line of bismuth-based high temperature superconductors

    SciTech Connect

    Mehdaoui, A.; Beille, J.; Berling, D.; Loegel, B.; Noudem, J.G.; Tournier, R.

    1997-09-01

    We discuss the magnetic properties of lead doped Bi-2223 bulk samples obtained through combined magnetic melt texturing and hot pressing (MMTHP). The ac complex susceptibility measurements are achieved over a broad ac field range (1 Oe{lt}h{sub ac}{lt}100 Oe) and show highly anisotropic properties. The intergranular coupling is improved in the direction perpendicular to the applied stress and magnetic field direction, and an intragranular loss peak is observed for the first time. A comparison is made with other bismuth-based compounds and it is shown that the MMTHP process shifts the ac irreversibility line (ac IL) toward higher fields. It is also shown that all the ac IL{close_quote}s for quasi 2D bismuth-based compounds show a nearly quadratic temperature dependence and deviate therefore strongly from the linear behavior observed in quasi 3D compounds and expected from a critical state model.{copyright} {ital 1997 Materials Research Society.}

  6. The marine diversity spectrum

    PubMed Central

    Reuman, Daniel C; Gislason, Henrik; Barnes, Carolyn; Mélin, Frédéric; Jennings, Simon

    2014-01-01

    Distributions of species body sizes within a taxonomic group, for example, mammals, are widely studied and important because they help illuminate the evolutionary processes that produced these distributions. Distributions of the sizes of species within an assemblage delineated by geography instead of taxonomy (all the species in a region regardless of clade) are much less studied but are equally important and will illuminate a different set of ecological and evolutionary processes. We develop and test a mechanistic model of how diversity varies with body mass in marine ecosystems. The model predicts the form of the ‘diversity spectrum’, which quantifies the distribution of species' asymptotic body masses, is a species analogue of the classic size spectrum of individuals, and which we have found to be a new and widely applicable description of diversity patterns. The marine diversity spectrum is predicted to be approximately linear across an asymptotic mass range spanning seven orders of magnitude. Slope −0·5 is predicted for the global marine diversity spectrum for all combined pelagic zones of continental shelf seas, and slopes for large regions are predicted to lie between −0·5 and −0·1. Slopes of −0·5 and −0·1 represent markedly different communities: a slope of −0·5 depicts a 10-fold reduction in diversity for every 100-fold increase in asymptotic mass; a slope of −0·1 depicts a 1·6-fold reduction. Steeper slopes are predicted for larger or colder regions, meaning fewer large species per small species for such regions. Predictions were largely validated by a global empirical analysis. Results explain for the first time a new and widespread phenomenon of biodiversity. Results have implications for estimating numbers of species of small asymptotic mass, where taxonomic inventories are far from complete. Results show that the relationship between diversity and body mass can be explained from the dependence of predation behaviour

  7. Heart Sound Biometric System Based on Marginal Spectrum Analysis

    PubMed Central

    Zhao, Zhidong; Shen, Qinqin; Ren, Fangqin

    2013-01-01

    This work presents a heart sound biometric system based on marginal spectrum analysis, which is a new feature extraction technique for identification purposes. This heart sound identification system is comprised of signal acquisition, pre-processing, feature extraction, training, and identification. Experiments on the selection of the optimal values for the system parameters are conducted. The results indicate that the new spectrum coefficients result in a significant increase in the recognition rate of 94.40% compared with that of the traditional Fourier spectrum (84.32%) based on a database of 280 heart sounds from 40 participants. PMID:23429515

  8. Heart sound biometric system based on marginal spectrum analysis.

    PubMed

    Zhao, Zhidong; Shen, Qinqin; Ren, Fangqin

    2013-02-18

    This work presents a heart sound biometric system based on marginal spectrum analysis, which is a new feature extraction technique for identification purposes. This heart sound identification system is comprised of signal acquisition, pre-processing, feature extraction, training, and identification. Experiments on the selection of the optimal values for the system parameters are conducted. The results indicate that the new spectrum coefficients result in a significant increase in the recognition rate of 94.40% compared with that of the traditional Fourier spectrum (84.32%) based on a database of 280 heart sounds from 40 participants. 

  9. Correlation between AC and DC transport properties of Mn substituted cobalt ferrite

    NASA Astrophysics Data System (ADS)

    Supriya, Sweety; Kumar, Sunil; Kar, Manoranjan

    2016-12-01

    The CoFe2-xMnxO4 compound is prepared by following the sol gel technique. The structural analysis through XRD and Rietveld has been confirmed for the single cubic phase having F d 3 ¯ m space group for CoFe2-xMnxO4 and also verified it through Raman spectroscopy measurements. The tetrahedral site observed to be red shifted with increase in Mn concentration in cobalt ferrite. All the XRD patterns have been analyzed by employing the Rietveld refinement technique. The particle size was found to be in the range of 30-40 nm. The electrical properties of polycrystalline CoFe2-xMnxO4 for x = 0.00, 0.10, 0.15, and 0.2, spinel ferrite was investigated by impedance spectroscopy. The influence of doping, frequency and temperature on the electrical transport properties of the CoFe2-xMnxO4 for x = 0.00, 0.10, 0.15, and 0.20 were investigated. The magnitude of Z' and Z″ decreases with increase in temperature. Only one semicircle is observed in each Cole Cole plot which reveals that ac conductivity is dominated by grains. The grain resistance and grain boundary resistance both were found to decrease as a function of temperature. Temperature variation of DC electrical conductivity follows the Arrhenius relationship. A detailed analysis of electrical parameters provides assistance in connecting information regarding the conduction mechanism as well as determination of both dielectric and magnetic transition temperatures in the substituted cobalt ferrite. Detailed analysis of ac impedance and DC resistivity measurement reveals that, the magnetic ordering temperature in the Mn substituted cobalt ferrite does not respond to the frequency of ac electrical signal; however, it responds to the DC resistivity. The correlation between ac impedance and DC resistivity has been established.

  10. Cascading failures in ac electricity grids.

    PubMed

    Rohden, Martin; Jung, Daniel; Tamrakar, Samyak; Kettemann, Stefan

    2016-09-01

    Sudden failure of a single transmission element in a power grid can induce a domino effect of cascading failures, which can lead to the isolation of a large number of consumers or even to the failure of the entire grid. Here we present results of the simulation of cascading failures in power grids, using an alternating current (AC) model. We first apply this model to a regular square grid topology. For a random placement of consumers and generators on the grid, the probability to find more than a certain number of unsupplied consumers decays as a power law and obeys a scaling law with respect to system size. Varying the transmitted power threshold above which a transmission line fails does not seem to change the power-law exponent q≈1.6. Furthermore, we study the influence of the placement of generators and consumers on the number of affected consumers and demonstrate that large clusters of generators and consumers are especially vulnerable to cascading failures. As a real-world topology, we consider the German high-voltage transmission grid. Applying the dynamic AC model and considering a random placement of consumers, we find that the probability to disconnect more than a certain number of consumers depends strongly on the threshold. For large thresholds the decay is clearly exponential, while for small ones the decay is slow, indicating a power-law decay.

  11. Cascading failures in ac electricity grids

    NASA Astrophysics Data System (ADS)

    Rohden, Martin; Jung, Daniel; Tamrakar, Samyak; Kettemann, Stefan

    2016-09-01

    Sudden failure of a single transmission element in a power grid can induce a domino effect of cascading failures, which can lead to the isolation of a large number of consumers or even to the failure of the entire grid. Here we present results of the simulation of cascading failures in power grids, using an alternating current (AC) model. We first apply this model to a regular square grid topology. For a random placement of consumers and generators on the grid, the probability to find more than a certain number of unsupplied consumers decays as a power law and obeys a scaling law with respect to system size. Varying the transmitted power threshold above which a transmission line fails does not seem to change the power-law exponent q ≈1.6 . Furthermore, we study the influence of the placement of generators and consumers on the number of affected consumers and demonstrate that large clusters of generators and consumers are especially vulnerable to cascading failures. As a real-world topology, we consider the German high-voltage transmission grid. Applying the dynamic AC model and considering a random placement of consumers, we find that the probability to disconnect more than a certain number of consumers depends strongly on the threshold. For large thresholds the decay is clearly exponential, while for small ones the decay is slow, indicating a power-law decay.

  12. Amorphous force transducers in ac applications

    NASA Astrophysics Data System (ADS)

    Meydan, T.; Overshott, K. J.

    1982-11-01

    The high stress sensitivity and high yield stress properties of amorphous ribbon materials make them suitable for magnetic sensors and tranducer applications. Recently the authors have shown that ac systems eliminate the offset voltage and drift problems of the previously published dc systems. Further investigations proved that these transducers could be operated with a linear characteristic up to 1000 g in multiwrap toroidal configurations. The cause of the transducing behavior of the materials was proved to be variation of permeability with stress. It was previously suggested that the optimum operating frequency of the ac transducers is dependent on the physical configuration of the core. Further investigations have shown that the optimum operating frequency is linearly dependent on the amplitude of the input signal to the transducer. Double-core systems have been previously described in the literature where one core acts as a dummy core and the force is applied to the active core. The disadvantage of the double-core system is that aging of the active core changes the performance of the transducer by as much as 10%. A new system will be presented which uses an accurate analog memory to reduce the ageing effect to a fraction of one percent.

  13. Transport AC Losses in Striated YBCO Coated Conductors (Postprint)

    DTIC Science & Technology

    2012-02-01

    AFRL-RZ-WP-TP-2012-0124 TRANSPORT AC LOSSES IN STRIATED YBCO COATED CONDUCTORS (POSTPRINT) G.A. Levin and P.N. Barnes Mechanical Energy...TRANSPORT AC LOSSES IN STRIATED YBCO COATED CONDUCTORS (POSTPRINT) 5a. CONTRACT NUMBER In-house 5b. GRANT NUMBER 5c. PROGRAM ELEMENT...2006. 14. ABSTRACT DC current-voltage characteristics and transport ac losses of striated and non-striated Y1Ba2Cu3O7-δ ( YBCO ) coated conductors

  14. Electromagnetic spectrum management system

    DOEpatents

    Seastrand, Douglas R.

    2017-01-31

    A system for transmitting a wireless countermeasure signal to disrupt third party communications is disclosed that include an antenna configured to receive wireless signals and transmit wireless counter measure signals such that the wireless countermeasure signals are responsive to the received wireless signals. A receiver processes the received wireless signals to create processed received signal data while a spectrum control module subtracts known source signal data from the processed received signal data to generate unknown source signal data. The unknown source signal data is based on unknown wireless signals, such as enemy signals. A transmitter is configured to process the unknown source signal data to create countermeasure signals and transmit a wireless countermeasure signal over the first antenna or a second antenna to thereby interfere with the unknown wireless signals.

  15. Autism spectrum disorders.

    PubMed

    Fitzgerald, Kara; Hyman, Mark; Swift, Kathie

    2012-09-01

    Autism spectrum disorders (ASDs) are collectively the most commonly diagnosed pediatric neurodevelopmental condition. ASDs include autism, pervasive developmental disorder-not otherwise specified (PDD-NOS), Rett syndrome and Asperger disorder. ASD is characterized by impaired communication and social interaction and may involve developmental delays and seizure disorders. Recent parent-reported diagnosis of ASD in the United States put it at higher levels (1:91) than previously thought, with its diagnosis in boys occurring 4 to 5 times more frequently than in girls (1:58).(1) CDC estimates are currently 1:110;(1) up from 1:150 in 2007.(2) Annual medical expenditures for those affected are generally four to six times greater than for those without ASD.(1) While twin studies demonstrate that genetics play a significant role in ASD, the impact of environment should not be underestimated, given the approximate 20-fold increase in incidence over the last 20 years.(3.)

  16. Spectrum of physics comprehension

    NASA Astrophysics Data System (ADS)

    Blasiak, W.; Godlewska, M.; Rosiek, R.; Wcislo, D.

    2012-05-01

    The paper presents the results of research on the relationship between self-assessed comprehension of physics lectures and final grades of junior high school students (aged 13-15), high school students (aged 16-18) and physics students at the Pedagogical University of Cracow, Poland (aged 21). Students' declared level of comprehension was measured during a physics lecture on a prearranged scale of 1-10 with the use of a personal response system designed for the purpose of this experiment. Through the use of this tool, we obtained about 2000 computer records of students' declared comprehension of a 45 min lecture, which we named ‘the spectrum of comprehension’. In this paper, we present and analyse the correlation between students' declared comprehension of the content presented in the lecture and their final learning results.

  17. Terahertz Spectrum of Trioxane

    NASA Astrophysics Data System (ADS)

    Klein, H.; Belov, S. P.; Winnewisser, G.

    1996-02-01

    The pure rotational spectrum of trioxane, (H2CO)3 the trimer of formaldehyde, has been recorded with high resolution in the frequency range between 326 and 947 GHz for the main isotopomer, the 13 C, and the 18O isotopic species in the vibrational ground state. These new high J and K data reveal that the molecule is fairly rigid. For the constants determinable from the recorded high J and K spectra (J = 90 and K = 75) the rotational constant B = 5273.257 180(33) MHz, the two quartic centrifugal distortion constants DJ, and DJK, and the three sextic constants HJ, HJK, and HKJ are needed in the fit to reproduce the measured spectra within experimental accuracy. In addition, for the 13C isotopomer the sextic constants HJK and HKJ are determined as well as the off-diagonal parameters d1 and d2.

  18. Ocean color spectrum calculations

    NASA Technical Reports Server (NTRS)

    Mccluney, W. R.

    1974-01-01

    There is obvious value in developing the means for measuring a number of subsurface oceanographic parameters using remotely sensed ocean color data. The first step in this effort should be the development of adequate theoretical models relating the desired oceanographic parameters to the upwelling radiances to be observed. A portion of a contributory theoretical model can be described by a modified single scattering approach based on a simple treatment of multiple scattering. The resulting quasisingle scattering model can be used to predict the upwelling distribution of spectral radiance emerging from the sea. The shape of the radiance spectrum predicted by this model for clear ocean water shows encouraging agreement with measurements made at the edge of the Sargasso Sea off Cape Hatteras.

  19. Microwave Spectrum of Hexafluoroisopropanol

    NASA Astrophysics Data System (ADS)

    Shahi, Abhishek; Mani, Devendra; Arunan, E.

    2012-06-01

    Hexafluoroisopropanol (HFIP) is an important organic solvent and probably the only solvent which can dissolve polythene. IR studies, on this molecule confirm the existence of antiperiplanar (ap) and synclinical (sc) conformers. We have observed pure rotational spectrum of this molecule and the fitted rotational constants (A= 2105.1208(11) MHz, B= 1053.9942(3) MHz, C= 932.3398(3) MHz) confirm the presence of ap conformer. There are many other observed lines which most probably corresponds to sc structure and due to the large amplitude motion of H-atom, some of these transitions show tunneling splitting. Work is in progress for the deuterated (OD) and C-13 isotopologues of the monomer. HFIP is expected to exhibit interesting hydrogen bonding properties and we are planning to investigate them by studying its complex with water. The results will be presented in this talk. H. Schaal, T. Höber, and M. A. Suhm, J. Phys. Chem. A 104, 265 (2000).

  20. Suicide in autism spectrum disorders.

    PubMed

    Richa, Sami; Fahed, Mario; Khoury, Elias; Mishara, Brian

    2014-01-01

    This review focuses on suicide in patients with Autism Spectrum Disorders (ASD) as well as risk factors and comorbidities of persons with ASD who have attempted suicide. Research was conducted by searching PubMed and Psychinfo for articles. Suicide in ASD is largely understudied. Although suicide is common in clinical samples, we have little knowledge of suicide in persons with ASD in the general population. Comorbidity, particularly with depression and other affective disorders or schizoid disorders and psychotic symptoms, is often reported, so it is difficult to determine if suicidality is associated with ASD or the comorbid disorder. Clinical samples suggest that suicide occurs more frequently in high functioning autism. Physical and sexual abuse, bullying, and changes in routine are precipitating events associated with suicide risk. Persons with ASD present risk factors inherent to their diagnosis (deficit in expression of feelings and thoughts), along with risk factors pertaining to the general population (abuse, depression, anxiety, etc.). The inability of persons with Pervasive Developmental Disorder (PDD) to express emotions and thoughts makes the diagnosis of suicidal ideation difficult and demands important adjustments to traditional psychotherapeutic interventions. More research is needed to determine the incidence of suicidal behaviors in persons with ASD, to identify risk and protective factors, as well as to assess the effectiveness of prevention strategies and interventions.

  1. THE SUBMILLIMETER SPECTRUM OF GLYCOLALDEHYDE

    SciTech Connect

    Carroll, P. Brandon; Widicus Weaver, Susanna L.; Drouin, Brian J. E-mail: susanna.widicus.weaver@emory.ed

    2010-11-01

    Glycolaldehyde (HOCH{sub 2}CHO) is a sugar-related interstellar prebiotic molecule that has been detected in two star-forming regions, Sgr B2(N) and G31.41+0.31. Glycolaldehyde is suspected to form from photodissociation-driven ice chemistry, and therefore can be used to trace complex organic chemistry in interstellar environments. The relative abundance of glycolaldehyde to its structural isomers, methyl formate (HCOOCH{sub 3}) and acetic acid (CH{sub 3}COOH), can be used to constrain astrochemical models. Given its central role in the complex chemistry of the interstellar medium, glycolaldehyde has been suggested as a prime molecular target for upcoming high-frequency molecular line searches using new far-infrared observatories. In particular, glycolaldehyde is a target for the Herschel Space Observatory HEXOS Key Program, which is conducting spectral line surveys of the Sgr B2(N) and Orion KL star-forming regions across the entire HIFI band. Laboratory investigation of glycolaldehyde in the HIFI frequency range is required before its lines can be identified in these spectra. We have therefore acquired the laboratory spectrum of glycolaldehyde in selected frequency ranges across the submillimeter range. We present here the laboratory spectral analysis of the ground vibrational state of glycolaldehyde up to 1.2 THz.

  2. The Submillimeter Spectrum of Glycolaldehyde

    NASA Astrophysics Data System (ADS)

    Carroll, P. Brandon; Drouin, Brian J.; Widicus Weaver, Susanna L.

    2010-11-01

    Glycolaldehyde (HOCH2CHO) is a sugar-related interstellar prebiotic molecule that has been detected in two star-forming regions, Sgr B2(N) and G31.41+0.31. Glycolaldehyde is suspected to form from photodissociation-driven ice chemistry, and therefore can be used to trace complex organic chemistry in interstellar environments. The relative abundance of glycolaldehyde to its structural isomers, methyl formate (HCOOCH3) and acetic acid (CH3COOH), can be used to constrain astrochemical models. Given its central role in the complex chemistry of the interstellar medium, glycolaldehyde has been suggested as a prime molecular target for upcoming high-frequency molecular line searches using new far-infrared observatories. In particular, glycolaldehyde is a target for the Herschel Space Observatory HEXOS Key Program, which is conducting spectral line surveys of the Sgr B2(N) and Orion KL star-forming regions across the entire HIFI band. Laboratory investigation of glycolaldehyde in the HIFI frequency range is required before its lines can be identified in these spectra. We have therefore acquired the laboratory spectrum of glycolaldehyde in selected frequency ranges across the submillimeter range. We present here the laboratory spectral analysis of the ground vibrational state of glycolaldehyde up to 1.2 THz.

  3. Ion transport study in polymer-nanocomposite films by dielectric spectroscopy and conductivity scaling

    NASA Astrophysics Data System (ADS)

    Tripathi, Namrata; Thakur, Awalendra K.; Shukla, Archana; Marx, David T.

    2015-07-01

    The dielectric and conductivity response of polymer nanocomposite electrolytes (films of PMMA4LiClO4 dispersed with nano-CeO2 powder) have been investigated. The dielectric behavior was analyzed via the dielectric permittivity (ε‧) and dissipation factor (tan δ) of the samples. The analysis has shown the presence of space charge polarization at lower frequencies. The real part of ac conductivity spectra of materials obeys the Jonscher power law. Parameters such as dc conductivity, hopping rate, activation energies and the concentration of charge carriers were determined from conductivity data using the Almond West formalism. It is observed that the higher ionic conductivity at higher temperature is due to increased thermally-activated hopping rates accompanied by a significant increase in carrier concentration. The contribution of carrier concentration to the total conductivity is also confirmed from activation energy of migration conduction and from Summerfield scaling. The ac conductivity results are also well correlated with TEM results.

  4. Effect of repetitive laser pulses on the electrical conductivity of intervertebral disc tissue

    SciTech Connect

    Omel'chenko, A I; Sobol', E N

    2009-03-31

    The thermomechanical effect of 1.56-{mu}m fibre laser pulses on intervertebral disc cartilage has been studied using ac conductivity measurements with coaxial electrodes integrated with an optical fibre for laser radiation delivery to the tissue. The observed time dependences of tissue conductivity can be interpreted in terms of hydraulic effects and thermomechanical changes in tissue structure. The laserinduced changes in the electrical parameters of the tissue are shown to correlate with the structural changes, which were visualised using shadowgraph imaging. Local ac conductivity measurements in the bulk of tissue can be used to develop a diagnostic/monitoring system for laser regeneration of intervertebral discs. (laser biology and medicine)

  5. The Conductivity of Solutions.

    ERIC Educational Resources Information Center

    Rayner-Canham, Geoff

    1993-01-01

    Presents historical background and modern explanations for the popular demonstration of showing conductivity of solutions through the insertion of a light-bulb conductivity tester into deionized water and water with salt in it. (PR)

  6. Fabrication of alumina films with laminated structures by ac anodization.

    PubMed

    Segawa, Hiroyo; Okano, Hironaga; Wada, Kenji; Inoue, Satoru

    2014-02-01

    Anodization techniques by alternating current (ac) are introduced in this review. By using ac anodization, laminated alumina films are fabricated. Different types of alumina films consisting of 50-200 nm layers were obtained by varying both the ac power supply and the electrolyte. The total film thickness increased with an increase in the total charge transferred. The thickness of the individual layers increased with the ac voltage; however, the anodization time had little effect on the film thickness. The laminated alumina films resembled the nacre structure of shells, and the different morphologies exhibited by bivalves and spiral shells could be replicated by controlling the rate of increase of the applied potentials.

  7. Fabrication of alumina films with laminated structures by ac anodization

    NASA Astrophysics Data System (ADS)

    Segawa, Hiroyo; Okano, Hironaga; Wada, Kenji; Inoue, Satoru

    2014-02-01

    Anodization techniques by alternating current (ac) are introduced in this review. By using ac anodization, laminated alumina films are fabricated. Different types of alumina films consisting of 50-200 nm layers were obtained by varying both the ac power supply and the electrolyte. The total film thickness increased with an increase in the total charge transferred. The thickness of the individual layers increased with the ac voltage; however, the anodization time had little effect on the film thickness. The laminated alumina films resembled the nacre structure of shells, and the different morphologies exhibited by bivalves and spiral shells could be replicated by controlling the rate of increase of the applied potentials.

  8. Dielectric and conducting behaviors in quasi-amorphous hybrid poly(diallyldimethylammonium phosphomolybdate)

    NASA Astrophysics Data System (ADS)

    Gao, Xiao-Yan; Liu, Shao-Xian; Xue, Chen; Li, Li; Zou, Yang; Liu, Jian-Lan; Ren, Xiao-Ming

    2016-11-01

    A quasi-amorphous inorganic-organic hybrid solid, which is comprised of poly(diallyldimethylammonium) polyelectrolyte cations with phosphomolybdates and denoted as PDDA/PMA, was prepared and characterized using elemental analysis, powder x-ray diffraction, IR spectrum, thermal and energy dispersive X-ray analyses. The PDDA/PMA exhibits multistep dielectric anomalies and dielectric relaxations. The dielectric anomaly around 353 K arises partially from the water trapped in the PDDA/PMA network releasing. The PDDA/PMA was further dried under vacuum at 373 K to give water-free sample PDDA/PMA-1. With water being removed, the broad anomaly peak around 353 K in the ε‧-T plot of PDDA/PMA changes into a platform in that of PDDA/PMA-1, indicating that the dielectric anomalies result from not only losing water but also the network disorder in PDDA/PMA-1. In addition, the platform strongly depends on the AC frequency in PDDA/PMA-1; the electric modulus and ion conductance analyses demonstrated that the dielectric relaxations at elevated temperature are related to the PMA ions displacing motion.

  9. Thermal conductivity and temperature profiles in carbon electrodes for supercapacitors

    NASA Astrophysics Data System (ADS)

    Burheim, Odne S.; Aslan, Mesut; Atchison, Jennifer S.; Presser, Volker

    2014-01-01

    The thermal conductivity of supercapacitor film electrodes composed of activated carbon (AC), AC with 15 mass% multi-walled carbon nanotubes (MWCNTs), AC with 15 mass% onion-like carbon (OLC), and only OLC, all mixed with polymer binder (polytetrafluoroethylene), has been measured. This was done for dry electrodes and after the electrodes have been saturated with an organic electrolyte (1 M tetraethylammonium-tetrafluoroborate in acetonitrile, TEA-BF4). The thermal conductivity data was implemented in a simple model of generation and transport of heat in a cylindrical cell supercapacitor systems. Dry electrodes showed a thermal conductivity in the range of 0.09-0.19 W K-1 m-1 and the electrodes soaked with an organic electrolyte yielded values for the thermal conductivity between 0.42 and 0.47 W K-1 m-1. It was seen that the values related strongly to the porosity of the carbon electrode materials. Modeling of the internal temperature profiles of a supercapacitor under conditions corresponding to extreme cycling demonstrated that only a moderate temperature gradient of several degrees Celsius can be expected and which depends on the ohmic resistance of the cell as well as the wetting of the electrode materials.

  10. Action spectrum for retinal thermal injury

    NASA Astrophysics Data System (ADS)

    Lund, David J.; Edsall, Peter R.

    1999-06-01

    The action spectrum for light-induced damage to the retina results from the wavelength dependence transmission of the preretinal ocular media, wavelength dependent absorption in retinal chromophores and chromatic aberration of the eye optics. While various light/tissue interaction mechanisms have been implicated, thermal mechanisms dominate in the red and near-infrared for all exposure durations and in the visible for exposures shorter than a few seconds. A number of investigators have measured the transmission of the eye and the spectra of retinal absorbers, and thermal models based on these data predict the broad features of the action spectrum. Dose/response studies with lasers and incoherent light sources, conducted over the past 10 years mainly validate the thermal models.

  11. Surface Conductive Glass.

    ERIC Educational Resources Information Center

    Tanaka, John; Suib, Steven L.

    1984-01-01

    Discusses the properties of surface-conducting glass and the chemical nature of surface-conducting stannic (tin) oxide. Also provides the procedures necessary for the preparation of surface-conducting stannic oxide films on glass substrates. The experiment is suitable for the advanced inorganic chemistry laboratory. (JN)

  12. Superfine resolution acoustooptic spectrum analysis

    NASA Technical Reports Server (NTRS)

    Ansari, Homayoon; Lesh, James R.

    1991-01-01

    High resolution spectrum analysis of RF signals is required in applications such as the search for extraterrestrial intelligence, RF interference monitoring, or general purpose decomposition of signals. Sub-Hertz resolution in three-dimensional acoustooptic spectrum analysis is theoretically and experimentally demonstrated. The operation of a two-dimensional acoustooptic spectrum analyzer is extended to include time integration over a sequence of CCD frames.

  13. A theoretical model for the production of Ac-225 for cancer therapy by photon-induced transmutation of Ra-226.

    PubMed

    Melville, G; Fan Liu, Sau; Allen, B J

    2006-09-01

    Radium needles that were once implanted into tumours as a cancer treatment are now obsolete and constitute a radioactive waste problem, as their half-life is 1600 years. We are investigating the reduction of radium by transmutation on a small scale by bombarding Ra-226 with high-energy photons from a medical linear accelerator (linac) to produce Ra-225, which subsequently decays to Ac-225, which can be used as a generator to produce Bi-213 for use in 'targeted alpha therapy' for cancer. This paper examines the possibility of producing Ac-225 with a linac using an accurate theoretical model in which the bremsstrahlung photon spectrum at 18 MV linac electron energy is convoluted with the corresponding photonuclear cross sections of Ra-226. The total integrated yield can then be obtained and is compared with a computer simulation. This study shows that at 18 MV, the photonuclear reaction on Ra-226 can produce low activities of Ac-225 with a linac. However, a high power linac with high current, pulse length and frequency is needed to produce practical amounts of Ac-225 and a useful reduction of Ra-226.

  14. Electrically conductive composite material

    DOEpatents

    Clough, R.L.; Sylwester, A.P.

    1988-06-20

    An electrically conductive composite material is disclosed which comprises a conductive open-celled, low density, microcellular carbon foam filled with a non-conductive polymer or resin. The composite material is prepared in a two-step process consisting of first preparing the microcellular carbon foam from a carbonizable polymer or copolymer using a phase separation process, then filling the carbon foam with the desired non-conductive polymer or resin. The electrically conductive composites of the present invention has a uniform and consistent pattern of filler distribution, and as a result is superior over prior art materials when used in battery components, electrodes, and the like. 2 figs.

  15. Electrically conductive composite material

    SciTech Connect

    Clough, R.L.; Sylwester, A.P.

    1989-05-23

    An electrically conductive composite material is disclosed which comprises a conductive open-celled, low density, microcellular carbon foam filled with a non-conductive polymer or resin. The composite material is prepared in a two-step process consisting of first preparing the microcellular carbon foam from a carbonizable polymer or copolymer using a phase separation process, then filling the carbon foam with the desired non-conductive polymer or resin. The electrically conductive composites of the present invention has a uniform and consistent pattern of filler distribution, and as a result is superior over prior art materials when used in battery components, electrodes, and the like. 2 figs.

  16. Electrically conductive composite material

    DOEpatents

    Clough, Roger L.; Sylwester, Alan P.

    1989-01-01

    An electrically conductive composite material is disclosed which comprises a conductive open-celled, low density, microcellular carbon foam filled with a non-conductive polymer or resin. The composite material is prepared in a two-step process consisting of first preparing the microcellular carbon foam from a carbonizable polymer or copolymer using a phase separation process, then filling the carbon foam with the desired non-conductive polymer or resin. The electrically conductive composites of the present invention has a uniform and consistant pattern of filler distribution, and as a result is superior over prior art materials when used in battery components, electrodes, and the like.

  17. AC impedance electrochemical modeling of lithium-ion positive electrodes.

    SciTech Connect

    Dees, D.; Gunen, E.; Abraham, D.; Jansen, A.; Prakash, J.; Chemical Engineering; IIT

    2004-01-01

    Under Department of Energy's Advanced Technology Development Program,various analytical diagnostic studies are being carried out to examine the lithium-ion battery technology for hybrid electric vehicle applications, and a series of electrochemical studies are being conducted to examine the performance of these batteries. An electrochemical model was developed to associate changes that were observed in the post-test analytical diagnostic studies with the electrochemical performance loss during testing of lithium ion batteries. While both electrodes in the lithium-ion cell have been studied using a similar electrochemical model, the discussion here is limited to modeling of the positive electrode. The positive electrode under study has a composite structure made of a layered nickel oxide (LiNi{sub 0.8}Co{sub 0.15}Al{sub 0.05}O{sub 2}) active material, a carbon black and graphite additive for distributing current, and a PVDF binder all on an aluminum current collector. The electrolyte is 1.2M LiPF{sub 6} dissolved in a mixture of EC and EMC and a Celgard micro-porous membrane is used as the separator. Planar test cells (positive/separator/negative) were constructed with a special fixture and two separator membranes that allowed the placement of a micro-reference electrode between the separator membranes [1]. Electrochemical studies including AC impedance spectroscopy were then conducted on the individual electrodes to examine the performance and ageing effects in the cell. The model was developed by following the work of Professor Newman at Berkeley [2]. The solid electrolyte interface (SEI) region, based on post-test analytical results, was assumed to be a film on the oxide and an oxide layer at the surface of the oxide. A double layer capacity was added in parallel with the Butler-Volmer kinetic expression. The pertinent reaction, thermodynamic, and transport equations were linearized for a small sinusoidal perturbation [3]. The resulting system of differential

  18. Development and test of the ASAT Bipropellant Attitude Control System (ACS) engine

    NASA Astrophysics Data System (ADS)

    Hodge, K. F.; Allen, K. A.; Hemmings, B.

    1993-06-01

    The recent Kinetic Energy Anti-Satellite (KE ASAT) Bipropellant Attitude Control System (ACS) Engine testing demonstrated and characterized performance and operational durability. Within the ASAT mission, the bipropellant engines are used to despin the missile after shroud deployment and to provide attitude control of the Kill Vehicle (KV) during all phases of the KV free flight. These engines provide all attitude control thrust from booster separation until target intercept. The ASAT ACS engine is unique both in the amount of on-time that the engine sees during a tactical mission scenario and the high thermal loads which result from performing two diametrically opposed missions with a single thruster - long steady state burns and very short response time pulse mode operations. Two flightweight ASAT ACS Bipropellant engines were individually tested in a developmental test program. Testing was conducted at ambient conditions. Hot-fire testing consisted of steady-state, mission duty cycle (MDC), Chamber Pressure (Pc) excursion, mixture ratio excursion, and pulse performance. Testing was conducted by Rockwell's Rocketdyne Division at the Santa Susana Field Laboratory (SSFL), Systems Test Laboratory IV (STL IV), Cell 37A. Two additional engine tests are planned and will include altitude testing. This paper will summarize engine development, component development testing, valve orificing and cold flow calibration, and engine hot-fire testing approach and results.

  19. Frequency Content and Characteristics of Ventricular Conduction

    PubMed Central

    Tereshchenko, Larisa G.; Josephson, Mark E.

    2015-01-01

    The spectrum of frequencies producing the QRS complex has not been fully explored. In this manuscript we review previous studies of QRS frequency content, and discuss our novel method of the conjoint analysis of the ECG signal in six dimensions: in the domain of three space dimensions, in time domain, and in frequency domain. Orbital frequency of QRS loop is introduced as a six-dimensional characteristic of ventricular conduction, which helped to reveal inapparent ventricular conduction, and to characterize electrophysiological substrate. In this paper, we review our novel method in the historical context. PMID:26364232

  20. Uncovering the Catalytic Direction of Chondroitin AC Exolyase

    PubMed Central

    Yin, Feng-Xin; Wang, Feng-Shan; Sheng, Ju-Zheng

    2016-01-01

    Glycosaminoglycans (GAGs) are polysaccharides that play vital functional roles in numerous biological processes, and compounds belonging to this class have been implicated in a wide variety of diseases. Chondroitin AC lyase (ChnAC) (EC 4.2.2.5) catalyzes the degradation of various GAGs, including chondroitin sulfate and hyaluronic acid, to give the corresponding disaccharides containing an Δ4-unsaturated uronic acid at their non-reducing terminus. ChnAC has been isolated from various bacteria and utilized as an enzymatic tool for study and evaluating the sequencing of GAGs. Despite its substrate specificity and the fact that its crystal structure has been determined to a high resolution, the direction in which ChnAC catalyzes the cleavage of oligosaccharides remain unclear. Herein, we have determined the structural cues of substrate depolymerization and the cleavage direction of ChnAC using model substrates and recombinant ChnAC protein. Several structurally defined oligosaccharides were synthesized using a chemoenzymatic approach and subsequently cleaved using ChnAC. The degradation products resulting from this process were determined by mass spectrometry. The results revealed that ChnAC cleaved the β1,4-glycosidic linkages between glucuronic acid and glucosamine units when these bonds were located on the reducing end of the oligosaccharide. In contrast, the presence of a GlcNAc-α-1,4-GlcA unit at the reducing end of the oligosaccharide prevented ChnAC from cleaving the GalNAc-β1,4-GlcA moiety located in the middle or at the non-reducing end of the chain. These interesting results therefore provide direct proof that ChnAC cleaves oligosaccharide substrates from their reducing end toward their non-reducing end. This conclusion will therefore enhance our collective understanding of the mode of action of ChnAC. PMID:26742844

  1. Spectrum handoff algorithm with imperfect spectrum sensing incognitive radio networks

    NASA Astrophysics Data System (ADS)

    Ma, Bin; Bao, Xiao-min; Xie, Xian-zhong

    2016-10-01

    To guarantee the quality of service of licensed users, the unlicensed users must vacate the occupied channel by spectrum handoff if licensed users appear in the licensed spectrum. However, spectrum sensing with false alarm and missed detection may lead to more inaccuracy problems when unlicensed users perform spectrum handoff. To improve the problems mentioned before, we utilize PRP M/G/1 queuing network model to propose a spectrum handoff algorithm with error data retransmission mechanism and analyze its performance by transmission delay and extended data delivery time. In addition, we discuss the relationship between false alarm probability, extended data delivery time and user traffic load and verify the effectiveness of the proposed algorithm.

  2. AcMNPV ac143 (odv-e18) is essential for mediating budded virus production and is the 30th baculovirus core gene.

    PubMed

    McCarthy, Christina B; Theilmann, David A

    2008-05-25

    Autographa californica multiple nucleopolyhedrovirus (AcMNPV) ac143 (odv-e18) is a late gene that encodes for a predicted 9.6 kDa structural protein that locates to the occlusion derived viral envelope and viral induced intranuclear microvesicles [Braunagel, S.C., He, H., Ramamurthy, P., and Summers, M.D. (1996). Transcription, translation, and cellular localization of three Autographa californica nuclear polyhedrosis virus structural proteins: ODV-E18, ODV-E35, and ODV-EC27. Virology 222, 100-114.]. In this study we demonstrate that ac143 is actually a previously unrecognized core gene and that it is essential for mediating budded virus production. To examine the role of ac143 in the baculovirus life cycle, we used the AcMNPV bacmid system to generate an ac143 knockout (KO) virus (AcBAC(ac142)(REP-ac143KO)). Fluorescence and light microscopy showed that infection by AcBAC(ac142)(REP-ac143KO) is limited to a single cell and titration assays confirmed that AcBAC(ac142)(REP-ac143KO) was unable to produce budded virus (BV). Progression to very late phases of the viral infection was evidenced by the development of occlusion bodies in the nuclei of transfected cells. This correlated with the fact that viral DNA replication was unaffected in AcBAC(ac142)(REP-ac143KO) transfected cells. The entire ac143 promoter, which includes three late promoter motifs, is contained within the ac142 open reading frame. Different deletion mutants of this region showed that the integrity of the ac142-ac143 core gene cluster was required for the bacmids to display wild-type patterns of viral replication, BV production and RNA transcription.

  3. AcMNPV ac143 (odv-e18) is essential for mediating budded virus production and is the 30th baculovirus core gene

    SciTech Connect

    McCarthy, Christina B.; Theilmann, David A.

    2008-05-25

    Autographa californica multiple nucleopolyhedrovirus (AcMNPV) ac143 (odv-e18) is a late gene that encodes for a predicted 9.6 kDa structural protein that locates to the occlusion derived viral envelope and viral induced intranuclear microvesicles [Braunagel, S.C., He, H., Ramamurthy, P., and Summers, M.D. (1996). Transcription, translation, and cellular localization of three Autographa californica nuclear polyhedrosis virus structural proteins: ODV-E18, ODV-E35, and ODV-EC27. Virology 222, 100-114.]. In this study we demonstrate that ac143 is actually a previously unrecognized core gene and that it is essential for mediating budded virus production. To examine the role of ac143 in the baculovirus life cycle, we used the AcMNPV bacmid system to generate an ac143 knockout (KO) virus (AcBAC{sup ac142REP-ac143KO}). Fluorescence and light microscopy showed that infection by AcBAC{sup ac142REP-ac143KO} is limited to a single cell and titration assays confirmed that AcBAC{sup ac142REP-ac143KO} was unable to produce budded virus (BV). Progression to very late phases of the viral infection was evidenced by the development of occlusion bodies in the nuclei of transfected cells. This correlated with the fact that viral DNA replication was unaffected in AcBAC{sup ac142REP-ac143KO} transfected cells. The entire ac143 promoter, which includes three late promoter motifs, is contained within the ac142 open reading frame. Different deletion mutants of this region showed that the integrity of the ac142-ac143 core gene cluster was required for the bacmids to display wild-type patterns of viral replication, BV production and RNA transcription.

  4. AC Magnetic Properties of Large Volume of Water — Susceptibility Measurement in Unshielded Environment

    NASA Astrophysics Data System (ADS)

    Tsukada, Keiji; Kiwa, Toshihiko; Masuda, Yuuki

    2006-10-01

    To investigate the effect of low-frequency magnetic-field exposure of a human body, the low-frequency AC magnetic property of a large volume of water was measured by low-frequency magnetic field exposure (from 50 Hz to 1.2 kHz). The results indicate that the AC magnetic property of water is due to diamagnetism in the low-frequency range. The phase between the main magnetic field and the generated magnetic field remained constant at about 180°. Results were not affected by conductivity or pH. Moreover, the magnetic-field strength from water showed a susceptibility frequency dependence proportional to the frequency above approximately 400 Hz. Because of the incremental effects of susceptibility, the magnetic field from water was measured using a conventional magnetic sensor (magnetic resistive; MR) in an unshielded environment.

  5. Comparative performance evaluation of advanced AC and DC EV propulsion systems

    NASA Astrophysics Data System (ADS)

    MacDowall, R. D.; Crumley, R. L.

    Idaho National Engineering Laboratory (INEL) evaluates EV propulsion systems and components for the U.S. Department of Energy (DOE) Electric and Hybrid Vehicle (EHV) Program. In this study, experimental data were used to evaluate the relative performances of the benchmark Chrysler/GE ETV-1 DC and the Ford/GE First Generation Single-Shaft AC (ETX-I) propulsion systems. Tests were conducted on the INEL's chassis dynamometer using identical aerodynamic and rolling resistance road-load coefficients and vehicle test weights. The results allowed a direct comparison of selected efficiency and performance characteristics for the two propulsion system technologies. The ETX-I AC system exhibited slightly lower system efficiency during constant speed testing than the ETV-1 DC propulsion system.

  6. Demonstration of an ac Josephson junction laser

    NASA Astrophysics Data System (ADS)

    Cassidy, M. C.; Bruno, A.; Rubbert, S.; Irfan, M.; Kammhuber, J.; Schouten, R. N.; Akhmerov, A. R.; Kouwenhoven, L. P.

    2017-03-01

    Superconducting electronic devices have reemerged as contenders for both classical and quantum computing due to their fast operation speeds, low dissipation, and long coherence times. An ultimate demonstration of coherence is lasing. We use one of the fundamental aspects of superconductivity, the ac Josephson effect, to demonstrate a laser made from a Josephson junction strongly coupled to a multimode superconducting cavity. A dc voltage bias applied across the junction provides a source of microwave photons, and the circuit’s nonlinearity allows for efficient down-conversion of higher-order Josephson frequencies to the cavity’s fundamental mode. The simple fabrication and operation allows for easy integration with a range of quantum devices, allowing for efficient on-chip generation of coherent microwave photons at low temperatures.

  7. Public Understanding of Chemistry, ACS National Meeting

    NASA Astrophysics Data System (ADS)

    Gettys, Nancy S.

    2000-06-01

    Three public events for area school-aged children were held on Saturday, March 25, 2000, prior to the opening of the 219th National Meeting of the American Chemical Society. All took place at the Moscone Convention Center in downtown San Francisco. The photographs tell the story: the programs were successful and a good time was had by all. Readers may be encouraged to try these ideas in their own area. If so, the local organizers of Carver Kidvention have additional information at www.scvacs.org/Carver/index.html or contact Howard Peters (Santa Clara Valley Section, ACS), peters4pa@aol.com. Additional photos of the Kidvention event may also be seen as supplemental material.

  8. Dielectric relaxation in AC powder electroluminescent devices

    NASA Astrophysics Data System (ADS)

    Zhang, Shuai; Su, Haibin; Tan, Chuan Seng; Wong, Terence Kin Shun; Teo, Ronnie Jin Wah

    2017-01-01

    The dielectric properties of AC powder electroluminescent devices were measured and analyzed using complex impedance spectroscopy to determine the relaxation processes occurring within the devices. The relaxation processes identified were ascribed to the electrode polarization caused by ion accumulation at the electrode/resin interfaces, the Maxwell-Wagner-Sillars effects at the (ZnS or BaTiO3) particle/resin interfaces, and the dipolar reorientation of polymer chains in the resin matrix. Each relaxation process was represented by its corresponding equivalent circuit component. Space charge polarization at the electrodes were represented by a Warburg element, a resistor, and a constant phase element. The resin matrix, ZnS/resin and BaTiO3/resin interfaces could each be modeled by a resistor and a capacitor in parallel. The simulated equivalent circuits for three different printed structures showed good fitting with their experimental impedance results.

  9. Advanced ac powertrain for electric vehicles

    SciTech Connect

    Slicker, J.M.; Kalns, L.

    1985-01-01

    The design of an ac propulsion system for an electric vehicle includes a three-phase induction motor, transistorized PWM inverter/battery charger, microprocessor-based controller, and two-speed automatic transaxle. This system was built and installed in a Mercury Lynx test bed vehicle as part of a Department of Energy propulsion system development program. An integral part of the inverter is a 4-kw battery charger which utilizes one of the bridge transistors. The overall inverter strategy for this configuration is discussed. The function of the microprocessor-based controller is described. Typical test results of the total vehicle and each of its major components are given, including system efficiencies and test track performance results.

  10. Fuzzy efficiency optimization of AC induction motors

    NASA Technical Reports Server (NTRS)

    Jani, Yashvant; Sousa, Gilberto; Turner, Wayne; Spiegel, Ron; Chappell, Jeff

    1993-01-01

    This paper describes the early states of work to implement a fuzzy logic controller to optimize the efficiency of AC induction motor/adjustable speed drive (ASD) systems running at less than optimal speed and torque conditions. In this paper, the process by which the membership functions of the controller were tuned is discussed and a controller which operates on frequency as well as voltage is proposed. The membership functions for this dual-variable controller are sketched. Additional topics include an approach for fuzzy logic to motor current control which can be used with vector-controlled drives. Incorporation of a fuzzy controller as an application-specific integrated circuit (ASIC) microchip is planned.

  11. Boston ACS Meeting, Chemical Education Program

    NASA Astrophysics Data System (ADS)

    Wildeman, Thomas R.; Torre, Frank; Smist, Julianne

    1998-11-01

    For those of us who had not been to Boston since the last ACS meeting it was surprising to see how vibrant the city was. The shops, restaurants, parks, and other attractions throughout the large inner city area made the meeting most enjoyable. Again, our banquet cruise of the harbor was blessed with excellent weather. The ship went out far enough so that we landlocked people could feel the waves. The entire program had a celebratory tone-two sessions marking the 70th birthday of Glenn Crosby, a memorial symposium celebrating the teaching innovations of Hubert Alyea, and the 75th anniversary of the Journal of Chemical Education (>p 1360). Content issues in upper division chemistry courses as well as general chemistry took up a large portion of the program. Some of the symposia are discussed in this article.

  12. ACS Internal CTE Monitor and Short Darks

    NASA Astrophysics Data System (ADS)

    Ogaz, Sara

    2012-10-01

    This is a continuation of Program 12386 and is to be executed once a cycle for internal CTE and short darks, respectively.INTERNAL CTE MONITOR:The charge transfer efficiency {CTE} of the ACS CCD detectors will decline as damage due to on-orbit radiation exposure accumulates. This degradation will be monitored once a cycle to determine the useful lifetime of the CCDs. All the data for this program is acquired using internal targets {lamps} only, so all of the exposures should be taken during Earth occultation time {but not during SAA passages}. This program emulates the ACS pre-flight ground calibration and post-launch SMOV testing {program 8948}, so that results from each epoch can be directly compared. Extended Pixel Edge Response {EPER} data will be obtained over a range of signal levels for the Wide Field Channel {WFC}. The signal levels are 125, 500, 1620, 5000, 10000, and 60000 electrons at gain 2.Since Cycle 18, this monitoring program was reduced {compared to 11881} considering that there is also an external CTE monitoring program.SHORT DARKS:To improve the pixel-based CTE model at signals below 10 DN, short dark frames are needed to obtain a statistically useful sample of clean, warm pixel trails. This program obtains a set of dark frames for each of the following exposure times: 66 s {60 s for some subarrays} and 339 s. These short darks and the 1040 s darks obtained from the CCD Daily Monitor will sample warm and hot pixels over logarithmically increasing brightness. Subarray short darks were newly added in Cycle 19 to study CTE tails in different subarray readout modes.

  13. ACS Internal CTE Monitor and Short Darks

    NASA Astrophysics Data System (ADS)

    Ogaz, Sara

    2013-10-01

    This is a continuation of Program 13156 and is to be executed once a cycle for internal CTE and short darks, respectively.INTERNAL CTE MONITOR:The charge transfer efficiency {CTE} of the ACS CCD detectors will decline as damage due to on-orbit radiation exposure accumulates. This degradation will be monitored once a cycle to determine the useful lifetime of the CCDs. All the data for this program is acquired using internal targets {lamps} only, so all of the exposures should be taken during Earth occultation time {but not during SAA passages}. This program emulates the ACS pre-flight ground calibration and post-launch SMOV testing {program 8948}, so that results from each epoch can be directly compared. Extended Pixel Edge Response {EPER} data will be obtained over a range of signal levels for the Wide Field Channel {WFC}. The signal levels are 125, 500, 1620, 5000, 10000, and 60000 electrons at gain 2.Since Cycle 18, this monitoring program was reduced {compared to 11881} considering that there is also an external CTE monitoring program.SHORT DARKS:To improve the pixel-based CTE model at signals below 10 DN, short dark frames are needed to obtain a statistically useful sample of clean, warm pixel trails. This program obtains a set of dark frames for each of the following exposure times: 66 s {60 s for some subarrays} and 339 s. These short darks and the 1040 s darks obtained from the CCD Daily Monitor will sample warm and hot pixels over logarithmically increasing brightness. Subarray short darks were added in Cycle 19 to study CTE tails in different subarray readout modes.

  14. ACS Internal CTE Monitor and Short Darks

    NASA Astrophysics Data System (ADS)

    Lian Lim, Pey

    2010-09-01

    INTERNAL CTE MONITOR:The charge transfer efficiency {CTE} of the ACS CCD detectors will decline as damage due to on-orbit radiation exposure accumulates. This degradation will be monitored once a cycle to determine the useful lifetime of the CCDs. All the data for this program is acquired using internal targets {lamps} only, so all of the exposures should be taken during Earth occultation time {but not during SAA passages}. This program emulates the ACS pre-flight ground calibration and post-launch SMOV testing {program 8948}, so that results from each epoch can be directly compared. Extended Pixel Edge Response {EPER} data will be obtained over a range of signal levels for the Wide Field Channel {WFC}. The signal levels are 125, 500, 1620, 5000, 10000, and 60000 electrons at gain 2.In Cycle 18, this monitoring program has been reduced {compared to 11881} considering that there is also an external CTE monitoring program. High Resolution Camera {HRC} is not available for observations. First Pixel Response {FPR} exposures are removed because they only provide serial CTE for WFC, which is not that useful. Pseudo-bias exposures are removed because they are not used. Signal levels 300, 700, 1000, 30000, and 45000.electrons are removed to reduce total orbits. Number of exposures per setting are reduced to 1 only. Amps BC are removed since amp dependence is not an issue for EPER.SHORT DARKS:To improve the pixel-based CTE model at signals below 10 DN, short dark frames are needed to obtain a statistically useful sample of clean, warm pixel trails. This program obtains 9 dark frames for each of the following exposure times: 33 s, 100 s, and 339 s. These short darks and the 1000 s darks obtained from the CCD Daily Monitor will sample warm and hot pixels over logarithmically increasing brightness.This is a continuation of Program 12327 and is to be executed once a cycle.

  15. ACS Internal CTE Monitor and Short Darks

    NASA Astrophysics Data System (ADS)

    Lian Lim, Pey

    2011-10-01

    This is a continuation of Program 12386 and is to be executed once a cycle for internal CTE and short darks, respectively.INTERNAL CTE MONITOR:The charge transfer efficiency {CTE} of the ACS CCD detectors will decline as damage due to on-orbit radiation exposure accumulates. This degradation will be monitored once a cycle to determine the useful lifetime of the CCDs. All the data for this program is acquired using internal targets {lamps} only, so all of the exposures should be taken during Earth occultation time {but not during SAA passages}. This program emulates the ACS pre-flight ground calibration and post-launch SMOV testing {program 8948}, so that results from each epoch can be directly compared. Extended Pixel Edge Response {EPER} data will be obtained over a range of signal levels for the Wide Field Channel {WFC}. The signal levels are 125, 500, 1620, 5000, 10000, and 60000 electrons at gain 2.Since Cycle 18, this monitoring program was reduced {compared to 11881} considering that there is also an external CTE monitoring program.SHORT DARKS:To improve the pixel-based CTE model at signals below 10 DN, short dark frames are needed to obtain a statistically useful sample of clean, warm pixel trails. This program obtains a set of dark frames for each of the following exposure times: 66 s {60 s for some subarrays} and 339 s. These short darks and the 1040 s darks obtained from the CCD Daily Monitor will sample warm and hot pixels over logarithmically increasing brightness. Subarray short darks are newly added in Cycle 19 to study CTE tails in different subarray readout modes.

  16. Electrical studies on silver based fast ion conducting glassy materials

    SciTech Connect

    Rao, B. Appa Kumar, E. Ramesh Kumari, K. Rajani Bhikshamaiah, G.

    2014-04-24

    Among all the available fast ion conductors, silver based glasses exhibit high conductivity. Further, glasses containing silver iodide enhances fast ion conducting behavior at room temperature. Glasses of various compositions of silver based fast ion conductors in the AgI−Ag{sub 2}O−[(1−x)B{sub 2}O{sub 3}−xTeO{sub 2}] (x=0 to1 mol% in steps of 0.2) glassy system have been prepared by melt quenching method. The glassy nature of the compounds has been confirmed by X-ray diffraction. The electrical conductivity (AC) measurements have been carried out in the frequency range of 1 KHz–3MHz by Impedance Analyzer in the temperature range 303–423K. The DC conductivity measurements were also carried out in the temperature range 300–523K. From both AC and DC conductivity studies, it is found that the conductivity increases and activation energy decreases with increasing the concentration of TeO{sub 2} as well as with temperature. The conductivity of the present glass system is found to be of the order of 10{sup −2} S/cm at room temperature. The ionic transport number of these glasses is found to be 0.999 indicating that these glasses can be used as electrolyte in batteries.

  17. SYNTH: A spectrum synthesizer

    NASA Astrophysics Data System (ADS)

    Hensley, W. K.; McKinnon, A. D.; Miley, H. S.; Panisko, M. E.; Savard, R. M.

    1993-10-01

    A computer code has been written at the Pacific Northwest Laboratory (PNL) to synthesize the results of typical gamma ray spectroscopy experiments. The code, dubbed SYNTH, allows a user to specify physical characteristics of a gamma ray source, the quantity of the nuclides producing the radiation, the source-to-detector distance and the presence of absorbers, the type and size of the detector, and the electronic set up used to gather the data. In the process of specifying the parameters needed to synthesize a spectrum, several interesting intermediate results are produced, including a photopeak transmission function versus energy, a detector efficiency curve, and a weighted list of gamma and x rays produced from a set of nuclides. All of these intermediate results are available for graphical inspection and for printing. SYNTH runs on personal computers. It is menu driven and can be customized to user specifications. SYNTH contains robust support for coaxial germanium detectors and some support for sodium iodide detectors. SYNTH is not a finished product. A number of additional developments are planned. However, the existing code has been compared carefully to spectra obtained from National Institute for Standards and Technology (NIST) certified standards with very favorable results. Examples of the use of SYNTH and several spectral results are presented.

  18. Fetal Alcohol Spectrum Disorders.

    PubMed

    Williams, Janet F; Smith, Vincent C

    2015-11-01

    Prenatal exposure to alcohol can damage the developing fetus and is the leading preventable cause of birth defects and intellectual and neurodevelopmental disabilities. In 1973, fetal alcohol syndrome was first described as a specific cluster of birth defects resulting from alcohol exposure in utero. Subsequently, research unequivocally revealed that prenatal alcohol exposure causes a broad range of adverse developmental effects. Fetal alcohol spectrum disorder (FASD) is the general term that encompasses the range of adverse effects associated with prenatal alcohol exposure. The diagnostic criteria for fetal alcohol syndrome are specific, and comprehensive efforts are ongoing to establish definitive criteria for diagnosing the other FASDs. A large and growing body of research has led to evidence-based FASD education of professionals and the public, broader prevention initiatives, and recommended treatment approaches based on the following premises:▪ Alcohol-related birth defects and developmental disabilities are completely preventable when pregnant women abstain from alcohol use.▪ Neurocognitive and behavioral problems resulting from prenatal alcohol exposure are lifelong.▪ Early recognition, diagnosis, and therapy for any condition along the FASD continuum can result in improved outcomes.▪ During pregnancy:◦no amount of alcohol intake should be considered safe;◦there is no safe trimester to drink alcohol;◦all forms of alcohol, such as beer, wine, and liquor, pose similar risk; and◦binge drinking poses dose-related risk to the developing fetus.

  19. Rotational Spectrum of Sarin

    NASA Astrophysics Data System (ADS)

    Walker, A. R. Hight; Suenram, R. D.; Samuels, Alan; Jensen, James; Ellzy, Michael W.; Lochner, J. Michael; Zeroka, Daniel

    2001-05-01

    As part of an effort to examine the possibility of using molecular-beam Fourier-transform microwave spectroscopy to unambiguously detect and monitor chemical warfare agents, we report the first observation and assignment of the rotational spectrum of the nerve agent Sarin (GB) (Methylphosphonofluoridic acid 1-methyl-ethyl ester, CAS #107-44-8) at frequencies between 10 and 22 GHz. Only one of the two low-energy conformers of this organophosphorus compound (C4H10FO2P) was observed in the rotationally cold (Trot<2 K) molecular beam. The experimental asymmetric-rotor ground-state rotational constants of this conformer are A=2874.0710(9) MHz, B=1168.5776(4) MHz, C=1056.3363(4) MHz (Type A standard uncertainties are given, i.e., 1σ), as obtained from a least-squares analysis of 74 a-, b-, and c-type rotational transitions. Several of the transitions are split into doublets due to the internal rotation of the methyl group attached to the phosphorus. The three-fold-symmetry barrier to internal rotation estimated from these splittings is 677.0(4) cm-1. Ab initio electronic structure calculations using Hartree-Fock, density functional, and Moller-Plesset perturbation theories have also been made. The structure of the lowest-energy conformer determined from a structural optimization at the MP2/6-311G** level of theory is consistent with our experimental findings.

  20. The Solar Convection Spectrum

    NASA Technical Reports Server (NTRS)

    Bachmann, Kurt T.

    2000-01-01

    I helped to complete a research project with NASA scientists Dr. David Hathaway (my mentor), Rick Bogart, and John Beck from the SOHO/SOI collaboration. Our published paper in 'Solar Physics' was titled 'The Solar Convection Spectrum' (April 2000). Two of my undergraduate students were named on the paper--Gavrav Khutri and Josh Petitto. Gavrav also wrote a short paper for the National Conference of Undergraduate Research Proceedings in 1998 using a preliminary result. Our main result was that we show no evidence of a scale of convection named 'mesogranulation'. Instead, we see only direct evidence for the well-known scales of convection known as graduation and supergranulation. We are also completing work on vertical versus horizontal flow fluxes at the solar surface. I continue to work on phase relationships of solar activity indicators, but I have not yet written a paper with my students on this topic. Along with my research results, I have developed and augmented undergraduate courses at Birmingham-Southern College by myself and with other faculty. We have included new labs and observations, speakers from NASA and elsewhere, new subject material related to NASA and space science. I have done a great deal of work in outreach, mostly as President and other offices in the Birmingham Astronomical Society. My work includes speaking, attracting speakers, giving workshops, and governing.

  1. PINS Spectrum Identification Guide

    SciTech Connect

    A.J. Caffrey

    2012-03-01

    The Portable Isotopic Neutron Spectroscopy—PINS, for short—system identifies the chemicals inside munitions and containers without opening them, a decided safety advantage if the fill chemical is a hazardous substance like a chemical warfare agent or an explosive. The PINS Spectrum Identification Guide is intended as a reference for technical professionals responsible for the interpretation of PINS gamma-ray spectra. The guide is divided into two parts. The three chapters that constitute Part I cover the science and technology of PINS. Neutron activation analysis is the focus of Chapter 1. Chapter 2 explores PINS hardware, software, and related operational issues. Gamma-ray spectral analysis basics are introduced in Chapter 3. The six chapters of Part II cover the identification of PINS spectra in detail. Like the PINS decision tree logic, these chapters are organized by chemical element: phosphorus-based chemicals, chlorine-based chemicals, etc. These descriptions of hazardous, toxic, and/or explosive chemicals conclude with a chapter on the identification of the inert chemicals, e.g. sand, used to fill practice munitions.

  2. Spectrum Roentgen Gamma

    NASA Astrophysics Data System (ADS)

    Predehl, P.; Pavlinsky, M.

    2014-07-01

    Spectrum Roentgen Gamma (SRG) is an X-ray astrophysical observatory, developed by Russia in collaboration with Germany. The mission will be launched in 2016 into a 6-month-period halo orbit around L2. The mission lifetime is planned to be more than seven years. While the first four years of the mission are devoted to an all sky survey, the rest of the mssion will be used for pointed observations. The payload consists of two X-ray telescopes, eROSITA and ART-XC. The eROSITA sky survey will be about 30 times more sensitive than ROSAT at energies between 0.5 and 2 keV, while in the hard band (2-8 keV) it will provide the first ever true imaging survey of the sky. The design driving science is the detection of large samples of galaxy clusters out to redshifts z>1 in order to study the large scale structure in the universe and test cosmological models including Dark Energy. ART-XC's role is to extend the energy range of eROSITA alone, thereby doubling the effective area in the critical 4-7 keV range. The harder response of ART-XC also facilitates the x-ray detection of obscured AGN. Both instruments are currently in the flight model and calibration phase.

  3. [Autism Spectrum Disorder and DSM-5: Spectrum or Cluster?].

    PubMed

    Kienle, Xaver; Freiberger, Verena; Greulich, Heide; Blank, Rainer

    2015-01-01

    Within the new DSM-5, the currently differentiated subgroups of "Autistic Disorder" (299.0), "Asperger's Disorder" (299.80) and "Pervasive Developmental Disorder" (299.80) are replaced by the more general "Autism Spectrum Disorder". With regard to a patient-oriented and expedient advising therapy planning, however, the issue of an empirically reproducible and clinically feasible differentiation into subgroups must still be raised. Based on two Autism-rating-scales (ASDS and FSK), an exploratory two-step cluster analysis was conducted with N=103 children (age: 5-18) seen in our social-pediatric health care centre to examine potentially autistic symptoms. In the two-cluster solution of both rating scales, mainly the problems in social communication grouped the children into a cluster "with communication problems" (51 % and 41 %), and a cluster "without communication problems". Within the three-cluster solution of the ASDS, sensory hypersensitivity, cleaving to routines and social-communicative problems generated an "autistic" subgroup (22%). The children of the second cluster ("communication problems", 35%) were only described by social-communicative problems, and the third group did not show any problems (38%). In the three-cluster solution of the FSK, the "autistic cluster" of the two-cluster solution differentiated in a subgroup with mainly social-communicative problems (cluster 1) and a second subgroup described by restrictive, repetitive behavior. The different cluster solutions will be discussed with a view to the new DSM-5 diagnostic criteria, for following studies a further specification of some of the ASDS and FSK items could be helpful.

  4. Probing the Sub-cycle AC Stark Shift by means of Attosecond Pulses: An ab initio Study of Transient Absorption

    NASA Astrophysics Data System (ADS)

    Zhao, Di; Telnov, Dmitry A.; Chu, Shih-I.

    2012-06-01

    We report a first fully ab initio theoretical exploration of the sub-cycle dynamical AC Stark shift and broadening of He atoms driven by an attosecond pulse and IR pulse. Since the duration of the UV pulse is much shorter than that of the optical cycle of the IR dressing laser field, the sub-cycle dynamics of the dressed atoms can be unfolded by applying the attosecond pulse at different time delay. A nonperturbative method is developed to calculate the transient absorption spectrum without weak-field limitation. By solving the time-dependent Schr"odinger equation accurately by means of the time-dependent generalized pseudospectral method, we predict novel sub-cycle laser-induced time-dependent AC Stark shift and power broadening of He atoms whose dynamical features are in good agreement with the latest ongoing experiments at UCF. Detailed results will be presented. This work is partially supported by DOE and NSF.

  5. Frequency Allocation; The Radio Spectrum.

    ERIC Educational Resources Information Center

    Federal Communications Commission, Washington, DC.

    The Federal Communications Commission (FCC) assigns segments of the radio spectrum to categories of users, and specific frequencies within each segment to individual users. Since demand for channel space exceeds supply, the process is complex. The radio spectrum can be compared to a long ruler: the portion from 10-540 kiloHertz has been set aside…

  6. Index of Spectrum Signature Data

    DTIC Science & Technology

    1985-05-01

    Frederick Research Corporation. Alexandria. VA 163 AN/APG-030 Radar Receiver Heasureaents Electromagnetic Coapatibilitv Analysis Center, US Navv Marine ... Electromagnetic Compatibility Characteristics of the W 86 Gun Fire Control Svstem. Naval HEapons Lab, Dahlgren, VA 501 Partial Spectrum Signature...ECAC-I-IO-(SS) DEPARTMENT OF DEFENSE Electromagnetic Compatibility Analysis Center Annapolis, Maryland 21402 INDEX OF SPECTRUM SIGNATURE DATA

  7. Wind-powered asynchronous AC/DC/AC converter system. [for electric power supply regulation

    NASA Technical Reports Server (NTRS)

    Reitan, D. K.

    1973-01-01

    Two asynchronous ac/dc/ac systems are modelled that utilize wind power to drive a variable or constant hertz alternator. The first system employs a high power 60-hertz inverter tie to the large backup supply of the power company to either supplement them from wind energy, storage, or from a combination of both at a preset desired current; rectifier and inverter are identical and operate in either mode depending on the silicon control rectifier firing angle. The second system employs the same rectification but from a 60-hertz alternator arrangement; it provides mainly dc output, some sinusoidal 60-hertz from the wind bus and some high harmonic content 60-hertz from an 800-watt inverter.

  8. 24 CFR Appendices A-C to Subtitle A - [Reserved

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 24 Housing and Urban Development 1 2010-04-01 2010-04-01 false A Appendices A-C to Subtitle A Housing and Urban Development Office of the Secretary, Department of Housing and Urban Development Appendices A-C to Subtitle A...

  9. 24 CFR Appendixes A-C to Subtitle A - [Reserved

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 24 Housing and Urban Development 1 2014-04-01 2014-04-01 false A Appendixes A-C to Subtitle A Housing and Urban Development Office of the Secretary, Department of Housing and Urban Development Appendixes A-C to Subtitle A...

  10. 24 CFR Appendices A-C to Subtitle A - [Reserved

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 24 Housing and Urban Development 1 2013-04-01 2013-04-01 false A Appendices A-C to Subtitle A Housing and Urban Development Office of the Secretary, Department of Housing and Urban Development Appendices A-C to Subtitle A...

  11. 24 CFR Appendices A-C to Subtitle A - [Reserved

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 24 Housing and Urban Development 1 2012-04-01 2012-04-01 false A Appendices A-C to Subtitle A Housing and Urban Development Office of the Secretary, Department of Housing and Urban Development Appendices A-C to Subtitle A...

  12. 24 CFR Appendices A-C to Subtitle A - [Reserved

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 24 Housing and Urban Development 1 2011-04-01 2011-04-01 false A Appendices A-C to Subtitle A Housing and Urban Development Office of the Secretary, Department of Housing and Urban Development Appendices A-C to Subtitle A...

  13. 21 CFR 880.5500 - AC-powered patient lift.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ...) MEDICAL DEVICES GENERAL HOSPITAL AND PERSONAL USE DEVICES General Hospital and Personal Use Therapeutic Devices § 880.5500 AC-powered patient lift. (a) Identification. An AC-powered lift is an electrically powered device either fixed or mobile, used to lift and transport patients in the horizontal or...

  14. Undergraduate Chemistry Education: Report of an ACS Presidential Symposium

    ERIC Educational Resources Information Center

    Polik, William F.

    2006-01-01

    The American Chemical Society (ACS) Presidential Symposium, Envisioning Undergraduate Chemistry Education in 2015 was organized by the ACS Committee on Professional Training (CPT), in response to the challenge to envision the chemistry enterprise in 2015. The need for more diverse role models at all levels is emphasized, including high school…

  15. 40 CFR Appendixes A-C to Part 403 - [Reserved

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 30 2013-07-01 2012-07-01 true A Appendixes A-C to Part 403 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) EFFLUENT GUIDELINES AND STANDARDS GENERAL PRETREATMENT REGULATIONS FOR EXISTING AND NEW SOURCES OF POLLUTION Appendixes A-C to Part 403...

  16. 34 CFR Appendices A-C to Part 682 - [Reserved

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 34 Education 4 2014-07-01 2014-07-01 false A Appendices A-C to Part 682 Education Regulations of the Offices of the Department of Education (Continued) OFFICE OF POSTSECONDARY EDUCATION, DEPARTMENT OF EDUCATION (CONTINUED) FEDERAL FAMILY EDUCATION LOAN (FFEL) PROGRAM Appendices A-C to Part 682...

  17. Operation of AC Adapters Visualized Using Light-Emitting Diodes

    ERIC Educational Resources Information Center

    Regester, Jeffrey

    2016-01-01

    A bridge rectifier is a diamond-shaped configuration of diodes that serves to convert alternating current(AC) into direct current (DC). In our world of AC outlets and DC electronics, they are ubiquitous. Of course, most bridge rectifiers are built with regular diodes, not the light-emitting variety, because LEDs have a number of disadvantages. For…

  18. 40 CFR Appendixes A-C to Part 403 - [Reserved

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 28 2010-07-01 2010-07-01 true A Appendixes A-C to Part 403 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) EFFLUENT GUIDELINES AND STANDARDS GENERAL PRE-TREAT-MENT REGULATIONS FOR EXIST-ING AND NEW SOURCES OF POLLUTION Appendixes A-C to Part 403...

  19. ACS Committee on Professional Training 1986 Annual Report.

    ERIC Educational Resources Information Center

    Chemical and Engineering News, 1987

    1987-01-01

    Presents data on the number of bachelor's, master's, and Ph.D. degrees in chemistry from institutions whose programs are approved by the American Chemical Society (ACS). Reviews the programs and activities endorsed by the ACS Board of Directors in April, 1986. (ML)

  20. 40 CFR Appendixes A-C to Part 403 - [Reserved

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 29 2011-07-01 2009-07-01 true A Appendixes A-C to Part 403 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) EFFLUENT GUIDELINES AND STANDARDS GENERAL PRE-TREAT-MENT REGULATIONS FOR EXIST-ING AND NEW SOURCES OF POLLUTION Appendixes A-C to Part 403...

  1. Solid-state ac-to-dc converter

    NASA Technical Reports Server (NTRS)

    Monroe, C. M.

    1970-01-01

    Converter uses solid-state ac-to-dc rectification circuitry, filter circuitry, a tuned transformer, ac chopper circuitry, and an automatic current-control network. It has a dc power source which operates from 5 to 100 percent load at a 72 to 94 input to output efficiency.

  2. Electrostatic coalescence system with independent AC and DC hydrophilic electrodes

    DOEpatents

    Hovarongkura, A. David; Henry, Jr., Joseph D.

    1981-01-01

    An improved electrostatic coalescence system is provided in which independent AC and DC hydrophilic electrodes are employed to provide more complete dehydration of an oil emulsion. The AC field is produced between an AC electrode array and the water-oil interface wherein the AC electrode array is positioned parallel to the interface which acts as a grounded electrode. The emulsion is introduced into the AC field in an evenly distributed manner at the interface. The AC field promotes drop-drop and drop-interface coalescence of the water phase in the entering emulsion. The continuous oil phase passes upward through the perforated AC electrode array and enters a strong DC field produced between closely spaced DC electrodes in which small dispersed droplets of water entrained in the continuous phase are removed primarily by collection at hydrophilic DC electrodes. Large droplets of water collected by the electrodes migrate downward through the AC electrode array to the interface. All phase separation mechanisms are utilized to accomplish more complete phase separation.

  3. Precursors of Short GRBs Registered by SPI-ACS/INTEGRAL

    NASA Astrophysics Data System (ADS)

    Minaev, P.; Pozanenko, A.

    2016-10-01

    We have searched for precursors in light curves of short gamma-ray bursts registered by SPI-ACS/INTEGRAL in 2002-2014. The portion of short bursts with precursor activity will be less than 0.4% from all short bursts registered by SPI-ACS.

  4. Distribution of Unlinked Receptor Sites for Transposed Ac Elements from the Bz-M2(ac) Allele in Maize

    PubMed Central

    Dooner, H. K.; Belachew, A.; Burgess, D.; Harding, S.; Ralston, M.; Ralston, E.

    1994-01-01

    We have shown before that the Ac element from the maize bz-m2(Ac) allele, located in the short arm of chromosome 9 (9S), transposes preferentially to sites that are linked to the bz donor locus. Yet, about half of the Ac transpositions recovered from bz-m2(Ac) are in receptor sites not linked to the donor locus. In this study, we have analyzed the distribution of those unlinked receptor sites. Thirty-seven transposed Ac (trAc) elements that recombined independently of the bz locus were mapped using a set of wx reciprocal translocations. We found that the distribution of unlinked receptor sites for trAs was not random. Ten trAcs mapped to 9L, i.e., Ac had transposed to sites physically, if not genetically, linked to the donor site. Among chromosomes other than 9, the Ac element of bz-m2(Ac) appeared to have transposed preferentially to certain chromosomes, such as 5 and 7, but infrequently to others, such as 1, the longest chromosome in the maize genome. The seven trAc elements in chromosome 5 were mapped relative to markers in 5S and 5L and localized to both arms of 5. We also investigated the transposition of Ac to the homolog of the donor chromosome. We found that Ac rarely transposes from bz-m2(Ac) to the homologous chromosome 9. The clustering of Ac receptor sites around the donor locus has been taken to mean that a physical association between the donor site and nearby receptor sites occurs during transposition. The preferential occurrence of 9L among chromosomes harboring unlinked receptor sites would be expected according to this model, since sites in 9L would tend to be physically closer to 9S than sites in other chromosomes. The nonrandom pattern seen among the remaining chromosomes could reflect an underlying nuclear architecture, i.e., an ordering of the chromosomes in the interphase nucleus, as suggested from previous cytological observations. PMID:8138163

  5. High conductance surge cable

    DOEpatents

    Murray, M.M.; Wilfong, D.H.; Lomax, R.E.

    1998-12-08

    An electrical cable for connecting transient voltage surge suppressors to electrical power panels. A strip of electrically conductive foil defines a longitudinal axis, with a length of an electrical conductor electrically attached to the metallic foil along the longitudinal axis. The strip of electrically conductive foil and the length of an electrical conductor are covered by an insulating material. For impedance matching purposes, triangular sections can be removed from the ends of the electrically conductive foil at the time of installation. 6 figs.

  6. High conductance surge cable

    DOEpatents

    Murray, Matthew M.; Wilfong, Dennis H.; Lomax, Ralph E.

    1998-01-01

    An electrical cable for connecting transient voltage surge suppressers to ectrical power panels. A strip of electrically conductive foil defines a longitudinal axis, with a length of an electrical conductor electrically attached to the metallic foil along the longitudinal axis. The strip of electrically conductive foil and the length of an electrical conductor are covered by an insulating material. For impedance matching purposes, triangular sections can be removed from the ends of the electrically conductive foil at the time of installation.

  7. The fate of fusion Cry1Ab/1Ac proteins from Bt-transgenic rice in soil and water.

    PubMed

    Liu, Yongbo; Li, Junsheng; Luo, Zunlan; Wang, Huaru; Liu, Fang

    2016-02-01

    Toxin proteins form transgenic crops entering into the environment are likely affect non-target organisms. To investigate the entry route and fate of fusion Cry1Ab/1Ac proteins from transgenic rice expressing insecticide toxins from Bacillus thuringiensis (Bt) in soil and water, we conducted greenhouse and field experiments in 2013 and 2014. Cry1Ab/1Ac proteins from Bt-transgenic rice in soil was found within a horizontal range of 25cm, where most of plant roots distributed. Concentration of Cry1Ab/1Ac proteins was lower in water than in soil in the greenhouse experiment, and no Cry1Ab/1Ac protein was detected in field water. Cry1Ab/1Ac concentration from rice straws was higher in ditch water than in distilled water due to the existence of aquatic organisms in ditch water. Bt proteins from transgenic crops enter into soil ecosystems mainly through root exudates and into aquatic ecosystems through plant residues, which determines Bt fate in the environment.

  8. APN1 is a functional receptor of Cry1Ac but not Cry2Ab in Helicoverpa zea

    PubMed Central

    Wei, Jizhen; Zhang, Min; Liang, Gemei; Wu, Kongming; Guo, Yuyuan; Ni, Xinzhi; Li, Xianchun

    2016-01-01

    Lepidopteran midgut aminopeptidases N (APNs) are phylogenetically divided into eight clusters, designated as APN1–8. Although APN1 has been implicated as one of the receptors for Cry1Ac in several species, its potential role in the mode of action of Cry2Ab has not been functionally determined so far. To test whether APN1 also acts as one of the receptors for Cry1Ac in Helicoverpa zea and even for Cry2Ab in this species, we conducted a gain of function analysis by heterologously expressing H. zea APN1 (HzAPN1) in the midgut and fat body cell lines of H. zea and the ovarian cell line of Spodoptera frugiperda (Sf9) and a loss of function analysis by RNAi (RNA interference) silencing of the endogenous APN1 in the three cell lines using the HzAPN1 double strand RNA (dsRNA). Heterologous expression of HzAPN1 significantly increased the susceptibility of the three cell lines to Cry1Ac, but had no effects on their susceptibility to Cry2Ab. Knocking down of the endogenous APN1 made the three cell lines resistant to Cry1Ac, but didn’t change cell lines susceptibility to Cry2Ab. The findings from this study demonstrate that HzAPN1 is a functional receptor of Cry1Ac, but not Cry2Ab. PMID:26755166

  9. Electrically conductive cellulose composite

    DOEpatents

    Evans, Barbara R.; O'Neill, Hugh M.; Woodward, Jonathan

    2010-05-04

    An electrically conductive cellulose composite includes a cellulose matrix and an electrically conductive carbonaceous material incorporated into the cellulose matrix. The electrical conductivity of the cellulose composite is at least 10 .mu.S/cm at 25.degree. C. The composite can be made by incorporating the electrically conductive carbonaceous material into a culture medium with a cellulose-producing organism, such as Gluconoacetobacter hansenii. The composites can be used to form electrodes, such as for use in membrane electrode assemblies for fuel cells.

  10. Successful enrichment of the ubiquitous freshwater acI Actinobacteria.

    PubMed

    Garcia, Sarahi L; McMahon, Katherine D; Grossart, Hans-Peter; Warnecke, Falk

    2014-02-01

    Actinobacteria of the acI lineage are often the numerically dominant bacterial phylum in surface freshwaters, where they can account for > 50% of total bacteria. Despite their abundance, there are no described isolates. In an effort to obtain enrichment of these ubiquitous freshwater Actinobacteria, diluted freshwater samples from Lake Grosse Fuchskuhle, Germany, were incubated in 96-well culture plates. With this method, a successful enrichment containing high abundances of a member of the lineage acI was established. Phylogenetic classification showed that the acI Actinobacteria of the enrichment belonged to the acI-B2 tribe, which seems to prefer acidic lakes. This enrichment grows to low cell densities and thus the oligotrophic nature of acI-B2 was confirmed.

  11. Sustainable AC/AC hybrid electrochemical capacitors in aqueous electrolyte approaching the performance of organic systems

    NASA Astrophysics Data System (ADS)

    Abbas, Qamar; Babuchowska, Paulina; Frąckowiak, Elżbieta; Béguin, François

    2016-09-01

    A high energy hybrid AC/AC electrochemical capacitor has been realized in aqueous Li2SO4+KI electrolyte mixture. Owing to the redox processes associated with the 2I-/I2 system, the positive electrode operates in narrow potential range and displays high capacity. During prolonged potentiostatic floating at 1.6 V, the hybrid cell demonstrates remarkably stable capacitance and resistance. Analyses by temperature programmed desorption after floating at 1.6 V proved that oxidation of the positive AC electrode is prevented by the use of Li2SO4+KI, which enables the maximum potential of this electrode to be shifted below the water oxidation potential. When charged at 0.2 A g-1 up to U = 1.6 V, the hybrid cell displays a high capacitance of 75 F g-1 (300 F g-1 per mass of one electrode) compared to 47 F g-1 (188 F g-1 per mass of one electrode) for a symmetric cell in Li2SO4. At 0.2 A g-1 up to 1.6 V, the hybrid capacitor in Li2SO4+KI displays an energy density of 26 Wh kg-1 which approaches the energy density of 30.9 Wh kg-1 measured when the same carbon is implemented in a capacitor using TEABF4/ACN electrolyte and charged up to 2.5 V.

  12. HVDC-AC system interaction from AC harmonics. Volume 1. Harmonic impedance calculations. Final report

    SciTech Connect

    Breuer, G D; Chow, J H; Lindh, C B; Miller, N W; Numrich, F H; Price, W W; Turner, A E; Whitney, R R

    1982-09-01

    Improved methods are needed to characterize ac system harmonic behavior for ac filter design for HVDC systems. The purpose of this General Electric Company RP1138 research is to evaluate the present filter design practice and to investigate methods for calculating system harmonic impedances. An overview of ac filter design for HVDC systems and a survey of literature related to filter design have been performed. Two methods for calculating system harmonic impedances have been investigated. In the measurement method, an instrumentation system for measuring system voltage and current has been assembled. Different schemes of using the measurements to calculate system harmonic impedances have been studied. In the analytical method, a procedure to include various operating conditions has been proposed. Computer programs for both methods have been prepared, and the results of the measurement and analytical methods analyzed. A conclusion of the project is that the measurement and analytical methods both provided reasonable results. There are correlations between the measured and analytical results for most harmonics, although there are discrepancies between the assumptions used in the two methods. A sensitivity approach has been proposed to further correlate the results. From the results of the analysis, it is recommended that both methods should be tested further. For the measurement method, more testing should be done to cover different system operating conditions. In the analytical method, more detailed models for representing system components should be studied. In addition, alternative statistical and sensitivity approaches should be attempted.

  13. An Ac transposon system based on maize chromosome 4S for isolating long-distance-transposed Ac tags in the maize genome.

    PubMed

    Wang, Fei; Li, Zhaoying; Fan, Jun; Li, Pengfei; Hu, Wei; Wang, Gang; Xu, Zhengkai; Song, Rentao

    2010-12-01

    Transposon tagging is an important tool for gene isolation and functional studies. In maize, several transposon-tagging systems have been developed, mostly using Activator/Dissociation (Ac/Ds) and Mutator systems. Here, we establish another Ac-based transposon system with the donor Ac tightly linked with sugary1 (su1) on maize chromosome 4S. Newly transposed Ac (tr-Acs) were detected based on a negative dosage effect, and long-distance-transposed Ac events were identified and isolated from the donor Ac by a simple backcross scheme. In this study, we identified 208 independent long-distance-transposed Ac lines. Thirty-one flanking sequences of these tr-Acs were isolated and localized in the maize genome. As found in previous studies, the tr-Acs preferentially inserted into genic sequences. The distribution of tr-Acs is not random. In our study, the tr-Acs preferentially transposed into chromosomes 1, 2, 9 and 10. We discuss the preferential distribution of tr-Acs from Ac systems. Our system is complementary to two other Ac-based regional-mutagenesis systems in maize, and the combined use of these systems will achieve an even and high-density distribution of Ac elements throughout the maize genome for functional-genomics studies.

  14. Fragile X spectrum disorders

    PubMed Central

    Lozano, Reymundo; Rosero, Carolina Alba; Hagerman, Randi J

    2014-01-01

    Summary The fragile X mental retardation 1 gene (FMR1), which codes for the fragile X mental retardation 1 protein (FMRP), is located at Xp27.3. The normal allele of the FMR1 gene typically has 5 to 40 CGG repeats in the 5′ untranslated region; abnormal alleles of dynamic mutations include the full mutation (> 200 CGG repeats), premutation (55–200 CGG repeats) and the gray zone mutation (45–54 CGG repeats). Premutation carriers are common in the general population with approximately 1 in 130–250 females and 1 in 250–810 males, whereas the full mutation and Fragile X syndrome (FXS) occur in approximately 1 in 4000 to 1 in 7000. FMR1 mutations account for a variety of phenotypes including the most common monogenetic cause of inherited intellectual disability (ID) and autism (FXS), the most common genetic form of ovarian failure, the fragile X-associated primary ovarian insufficiency (FXPOI, premutation); and fragile X-associated tremor/ataxia syndrome (FXTAS, premutation). The premutation can also cause developmental problems including ASD and ADHD especially in boys and psychopathology including anxiety and depression in children and adults. Some premutation carriers can have a deficit of FMRP and some unmethylated full mutation individuals can have elevated FMR1 mRNA that is considered a premutation problem. Therefore the term “Fragile X Spectrum Disorder” (FXSD) should be used to include the wide range of overlapping phenotypes observed in affected individuals with FMR1 mutations. In this review we focus on the phenotypes and genotypes of children with FXSD. PMID:25606363

  15. Ac-Induced Instability at the Xanthophyllic Locus of Tomato

    PubMed Central

    Peterson, P. W.; Yoder, J. I.

    1993-01-01

    To detect genomic instability caused by Ac elements in transgenic tomatoes, we used the incompletely dominant mutation Xanthophyllic-1 (Xa-1) as a whole plant marker gene. Xa-1 is located on chromosome 10 and in the heterozygote state causes leaves to be yellow. Transgenic Ac-containing tomato plants which differed in the location and number of their Ac elements were crossed to Xa-1 tester lines and F(1) progeny were scored for aberrant somatic sectoring. Of 800 test and control F(1) progeny screened, only four plants had aberrantly high levels of somatic sectors. Three of the plants had twin sectors consisting of green tissue adjacent to white tissue, and the other had twin sectors comprised of green tissue adjacent to tissue more yellow than the heterozygote background. Sectoring was inherited and the two sectoring phenotypes mapped to opposite homologs of chromosome 10; the green/yellow sectoring phenotype mapped in coupling to Xa-1 while the green/white sectoring phenotype mapped in repulsion. The two sectoring phenotypes cosegregated with different single, non-rearranged Acs, and loss of these Acs from the genome corresponded to the loss of sectoring. Sectoring was still observed after transposition of the Ac to a new site which indicated that sectoring was not limited to a single locus. In both sectored lines, meiotic recombination of the sectoring Ac to the opposite homolog caused the phenotype to switch between the green/yellow and the green/white phenotypes. Thus the two different sectoring phenotypes arose from the same Ac-induced mechanism; the phenotype depended on which chromosome 10 homolog the Ac was on. We believe that the twin sectors resulted from chromosome breakage mediated by a single intact, transposition-competent Ac element. PMID:8394266

  16. DC and ac electrical properties of the chalcogenide semiconductor Se0.9In0.1

    NASA Astrophysics Data System (ADS)

    El-Hakim, S. A.; El-Wahab, F. A.; Mohamed, A. S.; Kotkata, M. F.

    2003-07-01

    Se0.9In0.1 samples were prepared from their highly pure constituents, by ice-water quenching from the melts. Structural characterization using XRD and DTA has revealed a stable phase consisting of some crystalline clusters embedded in a glassy matrix with a single glass transition (Tg) at a temperature 320 K, an onset exothermic crystallization peak at 361 K, and a melting endotherm with a melting point at 473 K. The dc (ohmic contact region) and ac (50 Hz-80 kHz) conductivities were measured under vacuum as a function of temperature (from T < Tg down to LN2) for massive samples, 0.3-0.6 mm thick. Results of the space-charge-limited current and the electrical characteristics of both dc and ac conduction are given and discussed in the light of the temperature dependence of the conduction mechanism.

  17. Conduction in Polydiacetylene Bilayers.

    DTIC Science & Technology

    1979-12-04

    This indicates that the polymer backbone has little effect in the conduction machanism of a dark undoped sample but only comes into play upon...almost none to doping. This indicates that the polymer backbone has little effect in the conduction machanism of a dark undoped sample but only comes into

  18. Electrically conductive diamond electrodes

    DOEpatents

    Swain, Greg; Fischer, Anne ,; Bennett, Jason; Lowe, Michael

    2009-05-19

    An electrically conductive diamond electrode and process for preparation thereof is described. The electrode comprises diamond particles coated with electrically conductive doped diamond preferably by chemical vapor deposition which are held together with a binder. The electrodes are useful for oxidation reduction in gas, such as hydrogen generation by electrolysis.

  19. Conductive Critical Thinking

    ERIC Educational Resources Information Center

    Paetkau, Mark

    2007-01-01

    One of my goals as an instructor is to teach students critical thinking skills. This paper presents an example of a student-led discussion of heat conduction at the first-year level. Heat loss from a human head is calculated using conduction and radiation models. The results of these plausible (but wrong) models of heat transfer contradict what…

  20. Conductive fabric seal

    DOEpatents

    Livesay, Ronald Jason; Mason, Brandon William; Kuhn, Michael Joseph; Rowe, Nathan Carl

    2015-10-13

    Disclosed are several examples of a system and method for detecting if an article is being tampered with. Included is a covering made of a substrate that is coated with a layer of an electrically conductive material that forms an electrically conductive surface having an electrical resistance. The covering is configured to at least partially encapsulate the article such that the article cannot be tampered with, without modifying the electrical resistance of the electrically conductive surface of the covering. A sensing device is affixed to the electrically conductive surface of the covering and the sensing device monitors the condition of the covering by producing a signal that is indicative of the electrical resistance of the electrically conductive surface of the covering. A measured electrical resistance that differs from a nominal electrical resistance is indicative of a covering that is being tampered with and an alert is communicated to an observer.

  1. Conductive fabric seal

    DOEpatents

    Livesay, Ronald Jason; Mason, Brandon William; Kuhn, Michael Joseph; Rowe, Nathan Carl

    2017-04-04

    Disclosed are several examples of a system and method for detecting if an article is being tampered with. Included is a covering made of a substrate that is coated with a layer of an electrically conductive material that forms an electrically conductive surface having an electrical resistance. The covering is configured to at least partially encapsulate the article such that the article cannot be tampered with, without modifying the electrical resistance of the electrically conductive surface of the covering. A sensing device is affixed to the electrically conductive surface of the covering and the sensing device monitors the condition of the covering by producing a signal that is indicative of the electrical resistance of the electrically conductive surface of the covering. A measured electrical resistance that differs from a nominal electrical resistance is indicative of a covering that is being tampered with and an alert is communicated to an observer.

  2. Spectrum Efficiency Through Dynamic Spectrum Access Techniques (Briefing Charts)

    DTIC Science & Technology

    2014-06-01

    Prototype System Key Future Events • May 14 Support MSU visit to Edwards • Jun 14 Design Deep Dive • Oct 14 Presenting technical papers, ITC , San...SW; Digital Radio; MBFE Board • Oct 14 Presenting technical papers ITC , San Diego Description – SDR develops a tri-band (L,S,C) transceiver, with...report Key Future Events • Design capacity allocation algorithms • Oct 14 Presenting a technical paper at ITC , San Diego Description – ACS, with

  3. Audiological findings in patients with oculo-auriculo-vertebral spectrum.

    PubMed

    Sleifer, Pricila; Gorsky, Natalya de Souza; Goetze, Thayse Bienert; Rosa, Rafael Fabiano Machado; Zen, Paulo Ricardo Gazzola

    2015-01-01

    Introduction Oculo-auriculo-vertebral spectrum, also referred to as Goldenhar syndrome, is a condition characterized by alterations involving the development of the structures of the first and second branchial arches. The abnormalities primarily affect the face, the eyes, the spine, and the ears, and the auricular abnormalities are associated with possible hearing loss. Objective To analyze the audiological findings of patients with oculo-auriculo-vertebral spectrum through liminal pure-tone audiometry and speech audiometry test. Methods Cross-sectional study conducted on 10 patients with oculo-auriculo-vertebral spectrum and clinical findings on at least two of the following areas: orocraniofacial, ocular, auricular, and vertebral. All patients underwent tonal and vocal hearing evaluations. Results Seven patients were male and three were female; all had ear abnormalities, and the right side was the most often affected. Conductive hearing loss was the most common (found in 10 ears), followed by sensorineural hearing loss (in five ears), with mixed hearing loss in only one ear. The impairment of the hearing loss ranged from mild to moderate, with one case of profound loss. Conclusions The results show a higher frequency of conductive hearing loss among individuals with the oculo-auriculo-vertebral spectrum phenotype, especially moderate loss affecting the right side. Furthermore, research in auditory thresholds in the oculo-auriculo-vertebral spectrum is important in speech therapy findings about the disease to facilitate early intervention for possible alterations.

  4. Audiological Findings in Patients with Oculo-Auriculo-Vertebral Spectrum

    PubMed Central

    Sleifer, Pricila; Gorsky, Natalya de Souza; Goetze, Thayse Bienert; Rosa, Rafael Fabiano Machado; Zen, Paulo Ricardo Gazzola

    2014-01-01

    Introduction Oculo-auriculo-vertebral spectrum, also referred to as Goldenhar syndrome, is a condition characterized by alterations involving the development of the structures of the first and second branchial arches. The abnormalities primarily affect the face, the eyes, the spine, and the ears, and the auricular abnormalities are associated with possible hearing loss. Objective To analyze the audiological findings of patients with oculo-auriculo-vertebral spectrum through liminal pure-tone audiometry and speech audiometry test. Methods Cross-sectional study conducted on 10 patients with oculo-auriculo-vertebral spectrum and clinical findings on at least two of the following areas: orocraniofacial, ocular, auricular, and vertebral. All patients underwent tonal and vocal hearing evaluations. Results Seven patients were male and three were female; all had ear abnormalities, and the right side was the most often affected. Conductive hearing loss was the most common (found in 10 ears), followed by sensorineural hearing loss (in five ears), with mixed hearing loss in only one ear. The impairment of the hearing loss ranged from mild to moderate, with one case of profound loss. Conclusions The results show a higher frequency of conductive hearing loss among individuals with the oculo-auriculo-vertebral spectrum phenotype, especially moderate loss affecting the right side. Furthermore, research in auditory thresholds in the oculo-auriculo-vertebral spectrum is important in speech therapy findings about the disease to facilitate early intervention for possible alterations. PMID:25992144

  5. Psychopharmacology of autism spectrum disorders: a selective review.

    PubMed

    Mohiuddin, Sarah; Ghaziuddin, Mohammad

    2013-11-01

    While there is no cure for autism spectrum disorder, psychopharmacologic agents are often used with behavioral and educational approaches to treat its comorbid symptoms of hyperactivity, irritability, and aggression. Studies suggest that at least 50% of persons with autism spectrum disorder receive psychotropic medications during their life span. This selective review examines recent studies about the use of psychotropic medications in persons with autism spectrum disorder. The aim was to focus on randomized controlled trials conducted from 1990 to 2010 on this topic. A comprehensive literature search was performed using PubMed and Cochrane databases. Out of 105 studies identified for the review, only 24 were randomized controlled trials. Thus, despite the common use of these medications in autism spectrum disorder, more controlled studies are needed to determine their long-term efficacy and safety.

  6. Methods to Calculate Spectrum Similarity.

    PubMed

    Yilmaz, Şule; Vandermarliere, Elien; Martens, Lennart

    2017-01-01

    Scoring functions that assess spectrum similarity play a crucial role in many computational mass spectrometry algorithms. These functions are used to compare an experimentally acquired fragmentation (MS/MS) spectrum against two different types of target MS/MS spectra: either against a theoretical MS/MS spectrum derived from a peptide from a sequence database, or against another, previously acquired MS/MS spectrum. The former is typically encountered in database searching, while the latter is used in spectrum clustering and spectral library searching. The comparison between acquired versus theoretical MS/MS spectra is most commonly performed using cross-correlations or probability derived scoring functions, while the comparison of two acquired MS/MS spectra typically makes use of a normalized dot product, especially in spectrum library search algorithms. In addition to these scoring functions, Pearson's or Spearman's correlation coefficients, mean squared error, or median absolute deviation scores can also be used for the same purpose. Here, we describe and evaluate these scoring functions with regards to their ability to assess spectrum similarity for theoretical versus acquired, and acquired versus acquired spectra.

  7. Conductivity and modulus formulation in lithium modified bismuth zinc borate glasses

    NASA Astrophysics Data System (ADS)

    Dahiya, Sajjan; Punia, R.; Murugavel, S.; Maan, A. S.

    2016-05-01

    The conductivity and modulus formulation in lithium modified bismuth zinc borate glasses with compositions xLi2O-(50-x) Bi2O3-10ZnO-40B2O3 has been studied in the frequency range 0.1 Hz-1.5 × 105 Hz in the temperature range 573 K-693 K. The temperature and frequency dependent conductivity is found to obey Jonscher's universal power law for all the studied compositions, the dc conductivity (σdc), crossover frequency (ωH), and frequency exponent (s) have been estimated from the fitting of the experimental data of ac conductivity with Jonscher's universal power law. Enthalpy to dissociate the cation from its original site next to a charge compensating centre (Hf) and enthalpy of migration (Hm) have been estimated. It has been observed that number of charge carriers and ac conductivity in the lithium modified bismuth zinc borate glasses increases with increase in Li2O content. Further, the conduction mechanism in the glass sample with x = 0 may be due to overlapping large polaron tunneling, whereas, conduction mechanism in other studied glass samples more or less follows diffusion controlled relaxation model. The ac conductivity is scaled using σdc and ωH as the scaling parameter and is found that these are suitable scaling parameter for conductivity scaling. Non-Debye type relaxation is found prevalent in the studied glass system. Scaling of ac conductivity as well as electric modulus confirms the presence of different type of conduction mechanism in the glass samples with x = 0 and 5 from other studied samples. The activation energy of relaxation (ER) and dc conductivity (Edc) are almost equal, suggesting that polarons/ions have to overcome same barrier while relaxing and conducting.

  8. Neuromyelitis optica spectrum disorders

    PubMed Central

    Sepúlveda, Maria; Armangué, Thaís; Sola-Valls, Nuria; Arrambide, Georgina; Meca-Lallana, José E.; Oreja-Guevara, Celia; Mendibe, Mar; Alvarez de Arcaya, Amaya; Aladro, Yolanda; Casanova, Bonaventura; Olascoaga, Javier; Jiménez-Huete, Adolfo; Fernández-Fournier, Mireya; Ramió-Torrentà, Lluis; Cobo-Calvo, Alvaro; Viñals, Montserrat; de Andrés, Clara; Meca-Lallana, Virginia; Cervelló, Angeles; Calles, Carmen; Rubio, Manuel Barón; Ramo-Tello, Cristina; Caminero, Ana; Munteis, Elvira; Antigüedad, Alfredo R.; Blanco, Yolanda; Villoslada, Pablo; Montalban, Xavier; Graus, Francesc

    2016-01-01

    Objective: To (1) determine the value of the recently proposed criteria of neuromyelitis optica (NMO) spectrum disorder (NMOSD) that unify patients with NMO and those with limited forms (NMO/LF) with aquaporin-4 immunoglobulin G (AQP4-IgG) antibodies; and (2) investigate the clinical significance of the serologic status in patients with NMO. Methods: This was a retrospective, multicenter study of 181 patients fulfilling the 2006 NMO criteria (n = 127) or NMO/LF criteria with AQP4-IgG (n = 54). AQP4-IgG and myelin oligodendrocyte glycoprotein immunoglobulin G (MOG-IgG) antibodies were tested using cell-based assays. Results: Patients were mainly white (86%) and female (ratio 6.5:1) with median age at onset 39 years (range 10–77). Compared to patients with NMO and AQP4-IgG (n = 94), those with NMO/LF presented more often with longitudinally extensive transverse myelitis (LETM) (p < 0.001), and had lower relapse rates (p = 0.015), but similar disability outcomes. Nonwhite ethnicity and optic neuritis presentation doubled the risk for developing NMO compared with white race (p = 0.008) or LETM presentation (p = 0.008). Nonwhite race (hazard ratio [HR] 4.3, 95% confidence interval [CI] 1.4–13.6) and older age at onset were associated with worse outcome (for every 10-year increase, HR 1.7, 95% CI 1.3–2.2). Patients with NMO and MOG-IgG (n = 9) had lower female:male ratio (0.8:1) and better disability outcome than AQP4-IgG-seropositive or double-seronegative patients (p < 0.001). Conclusions: In patients with AQP4-IgG, the similar outcomes regardless of the clinical phenotype support the unified term NMOSD; nonwhite ethnicity and older age at onset are associated with worse outcome. Double-seronegative and AQP4-IgG-seropositive NMO have a similar clinical outcome. The better prognosis of patients with MOG-IgG and NMO suggests that phenotypic and serologic classification is useful. PMID:27144216

  9. Spectrum Policy: Provisions in the 2012 Spectrum Act

    DTIC Science & Technology

    2013-10-18

    mobile services and devices, such as real-time viewing of video on smartphones , can be improved in several ways. Examples include (1) providing new...from the sale of licenses of repurposed federal spectrum identified in the act will be directed first to the Spectrum Relocation Fund, to cover costs...of moving federal users, with the balance going to the Public Safety Trust Fund. Proceeds from the sale of advanced wireless service licenses in

  10. Cuprous Ion Conducting Montmorillonite- Polypyrrole Nanocomposites

    NASA Astrophysics Data System (ADS)

    Krishantha, D. M. M.; Rajapakse, R. M. G.; Tennakoon, D. T. B.; Bandara, W. M. A. T.; Thilakarathna, P. N. L.

    2006-06-01

    Solid state polymer-Silicate nanocomposite based on Polypyrrole-Cu+-montmorilonite were prepared and electrical properties were investigated. In this preparation, Na-montmorillonite (Na+-MMT) was purified by repeated washing with distilled water and the intergallery cations were exchanged for Cu(II). The cupric ions exchanged-MMT(Cu(II)-- MMT) was again exposed to pyrrole in aqueous acidic solution to yield polypyrrole-Cu+-MMT nanocomposite. DC polarization test and AC impedance measurement reveal that the materials are mixed conductors. The ionic conductivity is due to the motion of cuprous ions which is facilitated by microstructure of polypyrrrole present in the intergalleries. An electrochemical cell was fabricated using the materials which can be represented by Cu(s)/ Cu+-PPY-MMT/Cu2SO4 (s)/Na2SO4(S)-Na2S2O8(s)/ and gave a 1.00 V. The cell is rechargeable.

  11. Broad-spectrum antiviral agents

    PubMed Central

    Zhu, Jun-Da; Meng, Wen; Wang, Xiao-Jia; Wang, Hwa-Chain R.

    2015-01-01

    Development of highly effective, broad-spectrum antiviral agents is the major objective shared by the fields of virology and pharmaceutics. Antiviral drug development has focused on targeting viral entry and replication, as well as modulating cellular defense system. High throughput screening of molecules, genetic engineering of peptides, and functional screening of agents have identified promising candidates for development of optimal broad-spectrum antiviral agents to intervene in viral infection and control viral epidemics. This review discusses current knowledge, prospective applications, opportunities, and challenges in the development of broad-spectrum antiviral agents. PMID:26052325

  12. Enhanced compressive wideband frequency spectrum sensing for dynamic spectrum access

    NASA Astrophysics Data System (ADS)

    Liu, Yipeng; Wan, Qun

    2012-12-01

    Wideband spectrum sensing detects the unused spectrum holes for dynamic spectrum access (DSA). Too high sampling rate is the main challenge. Compressive sensing (CS) can reconstruct sparse signal with much fewer randomized samples than Nyquist sampling with high probability. Since survey shows that the monitored signal is sparse in frequency domain, CS can deal with the sampling burden. Random samples can be obtained by the analog-to-information converter. Signal recovery can be formulated as the combination of an L0 norm minimization and a linear measurement fitting constraint. In DSA, the static spectrum allocation of primary radios means the bounds between different types of primary radios are known in advance. To incorporate this a priori information, we divide the whole spectrum into sections according to the spectrum allocation policy. In the new optimization model, the minimization of the L2 norm of each section is used to encourage the cluster distribution locally, while the L0 norm of the L2 norms is minimized to give sparse distribution globally. Because the L2/L0 optimization is not convex, an iteratively re-weighted L2/L1 optimization is proposed to approximate it. Simulations demonstrate the proposed method outperforms others in accuracy, denoising ability, etc.

  13. Electrical Conductivity in Insulator

    NASA Astrophysics Data System (ADS)

    Sinha, Anil Kumar

    2003-03-01

    ABSTRACT In insulating solid(Plastic Sheet)of 0.73mm thickness, the conduction process was ohmic at low D.C. electric feilds, but the feild strength increased the conductivity became feild dependent at high feilds and it exhibited some conductivity and the variation in conduction current was none-ohmic.The mechanism of electron transfer between two metallic electrodes separated by insulating material has received considerable attention. The electron transfer current was studied on 0.73mm plastic sheet and(I-V),(log I-log V),(log J-E^1/2)and (log o- 1/T) relations have been studied and the value of slope,electronic dielectric constant and activation energy for nature of conduction mechanism and process have been determined.The electrical conductivity measurements were carried out at room temperature (32.5 celcius)under high D.C. electric feilds of the order of 10^6 volt/meter.The sample of insulator(plastic sheet) was sandwiched between the aluminium electrodes of designed experimental cell,The effect of very high varying feilds at 32.5 celcius temperature,the electrical conduction has been proposed on the data obtained.The non-ohmic behavior in the sample seemed to start at an electric feild 3x10^6 volt/meter.In this case on data obtained it was concluded that "SCHOTTKY EMISSION MECHANISM" has been proposed. The activation energy was calculated by plotting(log o-1/T)characterstics at running temperature and it was found 0.325ev which is less than 1.0,It confirms predominance of Electronic Conduction. I=current in ampere V=volt T=temperature O=conductivity

  14. AC Dielectric Properties and Positron Annihilation Study on Co and Ti Substitution Effect on Ca-Sr M-Hexaferrites

    NASA Astrophysics Data System (ADS)

    Mahmoud, K. R.; Eraky, M. R.

    2016-06-01

    The dependence of AC conductivity σ AC, dielectric constant έ, and dielectric loss tangent tan δ on frequency and composition have been investigated at room temperature for polycrystalline Ca0.5Sr0.5Co x Ti x Fe12 - 2 x O19 (where 0.0 ≤ x ≤ 0.8) hexaferrites. It was found that the parameters σ AC, ɛ ', and tan δ have maximum values at x = 0.4 of the Co and Ti substitution. The behavior of σ AC, ɛ ', and tan δ with frequency and composition was explained on the basis of the hopping conduction mechanism and the Koops model. Positron annihilation lifetime spectroscopy (PALS) was used to investigate the defects and changes in electron density for hexaferrite samples. The PAL parameters ( τ 1, I 1, τ 2, I 2, and mean lifetime) show that altering the doping percentage of the Co and Ti ions affects the size and concentration of defects. The results reveal that there are some large voids in the studied samples. The obtained results indicate the high sensitivity of the PALS technique to the enhanced structure changes with changing composition of the investigated samples and correlate the results with the measured electrical parameters.

  15. Bollgard II cotton: compositional analysis and feeding studies of cottonseed from insect-protected cotton (Gossypium hirsutum L.) producing the Cry1Ac and Cry2Ab2 proteins.

    PubMed

    Hamilton, Kathryn A; Pyla, Paul D; Breeze, Matthew; Olson, Tammy; Li, Menghe; Robinson, Edwin; Gallagher, Sean P; Sorbet, Roy; Chen, Yin

    2004-11-17

    Bollgard II cotton event 15985 producing the Cry1Ac and Cry2Ab2 proteins has been developed by genetic modification to broaden the spectrum of insects to which the plant is tolerant and to provide an insect resistance management tool to impede the onset of resistance. The purpose of this study was to evaluate the composition and nutrition of Bollgard II cotton, relative to the use for food and animal feed, compared to that of conventional cotton varieties. Compositional analyses were conducted to measure proximate, fiber, amino acid, fatty acid, gossypol, and mineral contents of cottonseed from a total of 14 U.S. field sites over two years. Compositional analysis results showed that the cottonseed and cottonseed oil from Bollgard II cotton were comparable in their composition to those of the conventional control cotton line and other commercial varieties. The composition data are supported by nutritional safety studies conducted with dairy cows, catfish, and quail. Results from these studies showed that Bollgard II performed similarly to the conventional control cotton varieties. These data demonstrate that Bollgard II cotton is compositionally and nutritionally equivalent to conventional cotton varieties. These data support the conclusion that Bollgard II cotton is as safe and nutritious as conventional cotton for food and feed use.

  16. Dielectric properties and charge transfer in (TlInSe2)0.1(TlGaTe2)0.9 for the DC and AC current

    NASA Astrophysics Data System (ADS)

    Mustafaeva, S. N.; Asadov, M. M.; Dzhabbarov, A. I.

    2014-06-01

    The experimental results of studying the temperature and frequency dependences of dc and ac conductivity as well as the dispersion of dielectric coefficients of the grown single crystals of the (TlInSe2)0.1(TlGaTe2)0.9 solid solution are presented. The nature of dielectric losses and the hopping charge transfer mechanism have been established, and parameters of localized states, such as the density of states near the Fermi level and their spread, the average time and the hopping length of charge carriers, and the concentration of deep traps responsible for dc and ac conductivity, have been evaluated.

  17. Connectivity between electrical conduction and thermally activated grain size evolution in Ho-doped CoFe2O4 ferrite

    NASA Astrophysics Data System (ADS)

    Panneer Muthuselvam, I.; Bhowmik, R. N.

    2010-11-01

    Ho-doped CoFe2O4 spinel ferrite has been synthesized by a combination of mechanical alloying and subsequent annealing of the alloyed powder in the temperature range 950 °C <= TAN <= 1200 °C. The grains of the nanocrystalline samples have been found in the single domain/pseudo-single domain state for TAN <= 1050 °C and multi-domain state for TAN >= 1100 °C. The room temperature Fourier transform infrared spectroscopy spectrum of the samples indicated substantial changes in the tetrahedral sites of the cubic spinel structure while the alloyed powder was annealed at different temperatures. Ac conductivity of the nano-grained samples has been studied in the frequency range 1 Hz-3 MHz and temperature range 303-523 K. This work has been specifically designed to highlight the properties of electrical conductivity in the annealed samples. Experimental results revealed a strong connectivity between electrical conduction and the single domain and multi-domain states of the grains.

  18. Trapping polar molecules in an ac trap

    SciTech Connect

    Bethlem, Hendrick L.; Veldhoven, Jacqueline van; Schnell, Melanie; Meijer, Gerard

    2006-12-15

    Polar molecules in high-field seeking states cannot be trapped in static traps as Maxwell's equations do not allow a maximum of the electric field in free space. It is possible to generate an electric field that has a saddle point by superposing an inhomogeneous electric field to an homogeneous electric field. In such a field, molecules are focused along one direction, while being defocused along the other. By reversing the direction of the inhomogeneous electric field the focusing and defocusing directions are reversed. When the fields are being switched back and forth at the appropriate rate, this leads to a net focusing force in all directions. We describe possible electrode geometries for creating the desired fields and discuss their merits. Trapping of {sup 15}ND{sub 3} ammonia molecules in a cylindrically symmetric ac trap is demonstrated. We present measurements of the spatial distribution of the trapped cloud as a function of the settings of the trap and compare these to both a simple model assuming a linear force and to full three-dimensional simulations of the experiment. With the optimal settings, molecules within a phase-space volume of 270 mm{sup 3} (m/s){sup 3} remain trapped. This corresponds to a trap depth of about 5 mK and a trap volume of about 20 mm{sup 3}.

  19. Installation considerations for IGBT AC drives

    SciTech Connect

    Skibinski, G.L.

    1997-06-01

    In the last four years, Adjustable Speed ac Drive (ASD) manufacturers have migrated from Bipolar Junction Transistor (BJT) semiconductors to Insulated Gate Bipolar Transistors (IGBTs) as the preferred Output switching device. The advantage of IGBTs over BJTs is that device rise and fall time switching capability is 5 - 10 times faster, resulting in lower device switching loss and a more efficient drive. However, for a similar motor cable length as the BJT drive, the faster output voltage risetime of the IGBT drive may increase the dielectric voltage stress on the motor and cable due to a phenomenon called reflected wave. Faster output dv/dt transitions of IGBT drives also increase the possibility for phenomenon such as increased Common Mode (CM) electrical noise, Electromagnetic Interference (EMI) problems and increased capacitive cable charging current problems. Also, recent experience suggests any Pulse Width Modulated (PWM) drive with a steep fronted output voltage wave form may increase motor shaft voltage and lead to a bearing current phenomenon known as fluting. This paper provides a basic understanding of these issues, as well as solutions, to insure a successful drive system installation.

  20. Cardiac conduction system

    MedlinePlus Videos and Cool Tools

    ... cardiac muscle cells in the walls of the heart that send signals to the heart muscle causing it to contract. The main components ... the cardiac conduction system's electrical activity in the heart.