Electrical transport in lead-free (Na0.5Bi0.5)1-xSrxTiO3 ceramics (x = 0, 0.01 and 0.02)

NASA Astrophysics Data System (ADS)

Dutkiewicz, E. M.; Suchanicz, J.; Konieczny, K.; Czaja, P.; Kluczewska, K.; Czternastek, H.; Antonova, M.; Sternberg, A.

2017-09-01

Lead-free (Na0.5Bi0.5)1xSrxTiO3 (x = 0, 0.01 and 0.02) ceramics were manufactured through a solid-state mixed oxide method and their ac (σac) and dc (σdc) electric conductivity were studied. It is shown that the low-frequency (100 Hz-1 MHz) ac conductivity obeys a power law σac ∼ ωs characteristic for disordered materials. Both the dc and ac conductivities have thermally activated character and possess linear parts with different activation energies. The calculated activation energies are attributed to different mechanism of conductivity. Frequency dependence of σdc and exponent s is reasonably interpreted by a correlated barrier hopping model. The NBT-ST system is expected to be a new promising candidate for lead-free electronic materials.

Unified conduction mechanism in unconventional VZnCaFeO glasses

NASA Astrophysics Data System (ADS)

Ahmed, E. M.; Abdel-Wahab, F.

2014-09-01

Unconventional glasses with (70-x)%V2O5 - x%ZnO-10%CaO-20%FeO compositions (where x=0, 2.5, 5, 7.5, 10, 12.5 and 15 mol %) were prepared by a normal melt-quench technique. We investigated the DC and AC conductivities of these glasses as functions of temperature and frequency. We have noted that activation energy and pre-exponential factor of the DC conductivity both vary with composition and satisfy Meyer-Neldel rule (MNR). The AC conductivity exhibited a universal dynamic response: σAC=Aωs. The obtained results of the DC, AC and exponent factor S were discussed in terms of the modified correlated barrier hopping model, which assumes that the relaxation time should contain a Meyer-Neldel rule term. An agreement between experimental and theoretical results suggests that the conduction mechanism could be hopping of polarons over barriers.

Synthesis, characterization and AC conductivity studies of silver doped conducting polyaniline/graphene/SrTiO3 composites

NASA Astrophysics Data System (ADS)

Vinay, K.; Shivakumar, K.; Ravikiran, Y. T.; Revanasiddappa, M.

2018-05-01

The present work is an investigation of ac conduction behaviour and dielectric response of Polyaniline/Ag/Graphene/SrTiO3 (PAGS) composite prepared by in-situ chemical oxidative interfacial polymerization using (NH4)2S2O8 as an oxidising agent at 0-5°C. The structural characterization of the samples was examined using FT-IR and XRD techniques. The ac conductivity and dielectric response of synthesized polymer composites were investigated at room temperature in the frequency range varying from 5 × 101 - 5 × 106 Hz using HIOKI make 3532-50 LCR Hi-tester. The ac conductivity increases with increase in frequency and follows the regular trend, the real dielectric constant (ɛ') and imaginary dielectric constant (ɛ'') decreases with increase in frequency and exhibits almost zero dielectric loss at higher frequencies, which suggests that the composite is a lossless material at frequencies beyond 3Hz.

Study of electrical properties of Sc doped BaFe12O19 ceramic using dielectric, impedance, modulus spectroscopy and AC conductivity

NASA Astrophysics Data System (ADS)

Gupta, Surbhi; Deshpande, S. K.; Sathe, V. G.; Siruguri, V.

2018-04-01

We present dielectric, complex impedance, modulus spectroscopy and AC conductivity studies of the compound BaFe10Sc2O19 as a function of temperature and frequency to understand the conduction mechanism. The variation in complex dielectric constant with frequency and temperature were analyzed on the basis of Maxwell-Wagner-Koop's theory and charge hopping between ferrous and ferric ions. The complex impedance spectroscopy study shows only grain contribution whereas complex modulus plot shows two semicircular arcs which indicate both grain and grain boundary contributions in conduction mechanism. AC conductivity has also been evaluated which follows the Jonscher's law. The activation energy calculated from temperature dependence of DC conductivity comes out to be Ea˜ 0.31eV.

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.

Studies on a.c. conductivity behaviour of milled carbon fibre reinforced epoxy gradient composites

NASA Astrophysics Data System (ADS)

Nigrawal, Archana; Sharma, Arun Kumar; Ojha, Pragya

2018-05-01

Temperature and frequency dependence of a.c. conductivity (σa.c) of milled carbon fibre (MCF) reinforced epoxy gradient composites has been studied in a wide temperature (30 to 150°C) and frequency range (1 to 10kHz). It is observed that the ac conductivity of composites increases with increase in temperature. Activation energy decreases from 0.55 eV to 0.43 eV on increase of MCF content from 0.45to 1.66 Vol%.

Dielectric and AC conductivity studies on SrBi4Ti4O15

NASA Astrophysics Data System (ADS)

Jose, Roshan; Saravanan, K. Venkata

2018-05-01

The four layered SrBi4Ti4O15 ceramics which belong to the aurivillius family of oxide was prepared by conventional solid state reaction technique. Analysis of the dielectric data as a function of temperature and frequency revealed normal phase transition. The frequency dependent ac conductivity follows Jonscher's universal power law. Frequency exponent (n), pre-exponential factor (A), bulk dc conductivity (σdc), and hopping frequency (ωp) were determined from the fitting curves. The variation of frequency exponent with temperature indicates that large polaron hopping mechanism up to curie-temperature, then its changes to small polaron hopping. The activation energies were calculated from ac conductivity, bulk dc conductivity and hopping frequency. The activation energies revealed that conductivity had contributions from migrations of oxygen vacancies, bismuth ion vacancies and strontium ion vacancies.

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.

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.

Ancillary care in public health intervention research in low-resource settings: researchers' practices and decision-making.

PubMed

Taylor, Holly A; Merritt, Maria W; Mullany, Luke C

2011-09-01

Little is known about researchers' practices regarding the provision of ancillary care (AC) in public health intervention studies they have conducted and the factors that influence their decisions about whether to provide ancillary care in low-resource settings. We conducted 52 in-person in-depth interviews with public health researchers. Data analysis was iterative and led to the identification of themes and patterns among themes. We found that researchers who conduct their research in the community setting are more likely to identify and plan for the AC needs of potential research subjects before a study begins, whereas those affiliated with a permanent facility are more likely to deliver AC to research subjects on an ad hoc basis. Our findings suggest that on the whole, at least for public health intervention research in low-resource settings, researchers conducting research in the community setting confront more complex ethical and operational challenges in their decision-making about AC than do researchers conducting facility-based studies.

Electrical conductivity and dielectric relaxation of 2-(antipyrin-4-ylhydrazono)-2-(4-nitrophenyl)acetonitrile

NASA Astrophysics Data System (ADS)

El-Menyawy, E. M.; Zedan, I. T.; Nawar, H. H.

2014-03-01

The electrical and dielectric properties of the synthesized 2-(antipyrin-4-ylhydrazono)-2-(4-nitrophenyl)acetonitrile (AHNA) have been studied. The direct and alternating current (DC and AC) conductivities and complex dielectric constant were investigated in temperature range 303-403 K. The AC conductivity and dielectric properties of AHNA were investigated over frequency range 100 Hz-5 MHz. From DC and AC measurements, electrical conduction is found to be a thermally activated process. The frequency-dependent AC conductivity obeys Jonscher's universal power law in which the frequency exponent decreases with increasing temperature. The correlated barrier hopping (CBH) is the predominant model for describing the charge carrier transport in which the electrical parameters are evaluated. The activation energy is found to decrease with increasing frequency. The behaviors of dielectric and dielectric loss are discussed in terms of a polarization mechanism. The dielectric loss shows frequency power law from which the maximum barrier height is determined as 0.19 eV in terms of the Guintini model.

AC and DC conductivity study on Ca substituted bismuth ferrite

NASA Astrophysics Data System (ADS)

Pandey, Rabichandra; Pradhan, Lagen Kumar; Kumar, Sunil; Kar, Manoranjan

2018-05-01

Bi0.95Ca0.05FeO3 multiferroic compound was synthesized by the citric acid modified sol-gel method. Crystal structure of Bi0.95Ca0.05FeO3 is studied by the X-ray diffraction (XRD) technique. The ac impedance analysis of the compound has been carried out in a wide range of frequency (100 Hz - 1MHz) as well as temperature (40-2500C). Frequency variation of dielectric constant at different temperatures can be understood by the modified Debye formula. The activation energy was found to be 0.48eV, which was obtained by employing Arrhenius equation. The AC conductivity of the sample follows the Johnscher's power law which indicates the presence of hopping type conduction in localized charged states. To understand the conduction mechanism with localized charge states, the DC resistivity data were analyzed by Mott's variable range hopping (VRH) model. The activation energy calculated from Debye relaxation time, AC conductivity and DC resistivity are comparable to each other.

AC and DC conductivity due to hopping mechanism in double ion doped ceramics

NASA Astrophysics Data System (ADS)

Rizwana, Mahboob, Syed; Sarah, P.

2018-04-01

Sr1-2xNaxNdxBi4Ti4O15 (x = 0.1, 0.2 and 0.4) system is prepared by sol gel method involving Pechini process of modified polymeric precursor method. Phase identification is done using X-ray diffraction. Conduction in prepared materials involves different mechanisms and is explained through detailed AC and DC conductivity studies. AC conductivity studies carried out on the samples at different frequencies and different temperatures gives more information about electrical transport. Exponents used in two term power relation helps us to understand the different hopping mechanism involved at low as well as high frequencies. Activation energies calculated from the Arrhenius plots are used to calculate activation energies at different temperatures and frequencies. Hopping frequency calculated from the measured data explains hopping of charge carriers at different temperatures. DC conductivity studies help us to know the role of oxygen vacancies in conduction.

Effects of sintering temperature on electrical properties of sheep enamel hydroxyapatite

NASA Astrophysics Data System (ADS)

Dumludag, F.; Gunduz, O.; Kılıc, O.; Kılıc, B.; Ekren, N.; Kalkandelen, C.; Oktar, F. N.

2017-12-01

Bioceramics, especially calcium phosphate based bioceramics, whose examples are hydroxyapatite, and calcium phosphate powders have been widely used in the biomedical engineering applications. Hydroxyapatite (HA) is one of the most promising biomaterials, which are derived from natural sources, chemical method, animal like dental enamel and corals. The influence of sintering temperature on the electrical properties (i.e. DC conductivity, AC conductivity) of samples of sintered sheep enamel (SSSE) was studied in air and in vacuum ambient at room temperature. The sheep enamel were sintered at varying temperatures between 1000°C and 1300°C. DC conductivity results revealed that while dc conductivity of the SSSE decreases with increasing the sintering temperature in air ambient the values increased with increasing the sintering temperature in vacuum ambient. AC conductivity measurements were performed in the frequency range of 40 Hz - 105 Hz. The results showed that ac conductivity values decrease with increasing the sintering temperature.

Electron beam irradiated polymer electrolyte film: Morphology, dielectric and AC conductivity studies

NASA Astrophysics Data System (ADS)

Yesappa, L.; Niranjana, M.; Ashokkumar, S. P.; Vijeth, H.; Ganesh, S.; Devendrappa, H.

2018-05-01

The polymer (PVdF-co-HFP: LiClO4=90:10, PHL10) electrolyte films prepared by solution casting method and studied morphology, dielectric properties and ac conductivity before and after electron beam (EB) irradiation. The polarized optical micrographs reveals size of spherulite reduced with increasing EB dose represents increase in amorphousity. The dielectric measurements were studied at different temperatures and observed increase with frequency at different temperatures upon EB irradiation. The ac conductivity increases with frequency due to effect of EB dose.

Zinc chloride modified electronic transport and relaxation studies in barium-tellurite glasses

NASA Astrophysics Data System (ADS)

Dhankhar, Sunil; Kundu, R. S.; Rani, Sunita; Sharma, Preeti; Murugavel, S.; Punia, Rajesh; Kishore, N.

2017-09-01

The ac conductivity of halide based tellurium glasses having composition 70 TeO2-(30-x) BaO-x ZnCl2; x = 5, 10, 15, 20 and 25 has been investigated in the frequency range 10-1 Hz to 105Hz and in the temperature range 453 K to 553 K. The frequency and temperature dependent ac conductivity show mixed behaviour with increase in halide content and found to obey Jonscher's universal power law. The values of dc conductivity, crossover frequency and frequency exponent have been estimated from the fitting of experimental data of ac conductivity with Jonscher's universal power law. For determining the conduction mechanism in studied glass system, frequency exponent has been analyzed by various theoretical models. In presently studied glasses, the ac conduction takes place via overlapping large polaron tunneling (OLPT). The values of activation energy for dc conduction (W) and the one associated with relaxation process ( E R) are found to increase with increase in x up to glass sample with x = 15 and thereafter it decrease with increase in zinc chloride content. DC conduction takes place via variable range hopping (VRH) as proposed by Mott with some modification suggested by Punia et al. The value of real part of modulus ( M') is observed to decrease with increase in temperature. The value of stretched exponent (β) obtained from fitting of M'' reveals the presence of non-Debye type of relaxation in presently studied glass samples. Scaling spectra of ac conductivity and values of electric modulus ( M' and M'') collapse into a single master curve for all the compositions and temperatures. The values of relaxation energy ( E R) for all the studied glass compositions are almost equal to W, suggesting that polarons have to overcome same barrier while relaxing and conducting. The conduction and relaxation processes in the studied glass samples are composition and temperature independent. [Figure not available: see fulltext.

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

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

Structural, ac conductivity and dielectric properties of 3-formyl chromone

NASA Astrophysics Data System (ADS)

Ali, H. A. M.

2017-07-01

The structure for the powder of 3-formyl chromone was examined by X-ray diffraction technique in the 2θ° range ( 4° - 60° . The configuration of Al/3-formyl chromone/Al samples was designed. The electrical and dielectric properties were studied as a function of frequency (42- 5 × 106 Hz) and temperature (298-408K). The ac conductivity data of bulk of 3-formyl chromone varies as a power law with the frequency at different temperatures. The predominant mechanism for ac conduction was deduced. The ac conductivity shows a thermally activated process at different frequencies. The dielectric constant and dielectric loss were determined using the capacitance and dissipation factor measurements at different temperatures. The dielectric loss shows a peak of relaxation time that shifted to higher frequency with an increase in the temperature. The activation energy of the relaxation process was estimated.

Contribution of Vestibular-Evoked Myogenic Potential (VEMP) testing in the assessment and the differential diagnosis of otosclerosis.

PubMed

Tramontani, Ourania; Gkoritsa, Eleni; Ferekidis, Eleftherios; Korres, Stavros G

2014-02-07

The aim of this prospective clinical study was to evaluate the clinical importance of Vestibular-Evoked Myogenic Potentials (VEMPs) in the assessment and differential diagnosis of otosclerosis and otologic diseases characterized by "pseudo-conductive" components. We also investigated the clinical appearance of balance disorders in patients with otosclerosis by correlating VEMP results with the findings of caloric testing and pure tone audiometry(PTA). Air-conducted(AC) 4-PTA, bone-conducted(BC) 4-PTA, air-bone Gap(ABG), AC, BC tone burst evoked VEMP, and calorics were measured preoperatively in 126 otosclerotic ears. The response rate of the AC-VEMPs and BC-VEMPs was 29.36% and 44.03%, respectively. Statistical differences were found between the means of ABG, AC 4-PTA, and BC 4-PTA in the otosclerotic ears in relation to AC-VEMP elicitability. About one-third of patients presented with disequilibrium. A statistically significant interaction was found between calorics and dizziness in relation to PTA thresholds. No relationship was found between calorics and dizziness with VEMPs responses. AC and BC VEMPs can be elicited in ears with otosclerosis. AC-VEMP is more vulnerable to conductive hearing loss. Evaluation of AC-VEMP thresholds can be added in the diagnostic work-up of otosclerosis in case of doubt, enhancing differential diagnosis in patients with air-bone gaps. Otosclerosis is not a cause of canal paresis or vertigo.

Comparative studies of the structure, morphology and electrical conductivity of polyaniline weakly doped with chlorocarboxylic acids

NASA Astrophysics Data System (ADS)

Gmati, Fethi; Fattoum, Arbi; Bohli, Nadra; Dhaoui, Wadia; Belhadj Mohamed, Abdellatif

2007-08-01

We report the results of studies on two series of polyaniline (PANI), doped with dichloroacetic (DCA) and trichloroacetic (TCA) acids, respectively, at various doping rates and obtained by the in situ polymerization method. Samples were characterized by x-ray diffraction, scanning electron microscopy and conductivity measurements. The direct current (dc) and alternating current (ac) electrical conductivities of PANI salts have been investigated in the temperature range 100-310 K and frequency range 7-106 Hz. The results of this study indicate better chain ordering and higher conductivity for PANI doped with TCA. The dc conductivity of all samples is suitably fitted to Mott's three-dimensional variable-range hopping (VRH) model. Different Mott parameters such as characteristic temperature T0, density of states at the Fermi level (N(EF)), average hopping energy (W) and the average hopping distance (R) have been evaluated. The dependence of such values on the dopant acid used is discussed. At high frequencies, the ac conductivity follows the power law σac(ω,T) = A(T)ωs(T,ω), which is characteristic for charge transport in disordered materials by hopping or tunnelling processes. The observed increase in the frequency exponent s with temperature suggests that the small-polaron tunnelling model best describes the dominant ac conduction mechanism. A direct correlation between conductivity, structure and morphology was obtained in our systems.

[Air conducted ocular VEMP: I. Determination of a method and application in normal patients].

PubMed

Walther, L E; Schaaf, H; Sommer, D; Hörmann, K

2011-07-01

Air conducted (AC) cervical vestibular evoked myogenic potentials (AC cVEMP) and air conducted ocular VEMP (AC oVEMP) may be used for measurement of otolith function. However AC oVEMP are few examined till now. The aim of this pilot study was to apply a method for use of AC oVEMP in clinical practice. AC oVEMP were recorded in healthy voluntary people (n=20) using intense AC-sound stimulation (500 Hz tone bursts, 100 dB nHL). Thermal irrigation and AC cVEMP were normal as including criteria. Values were evaluated statistically. AC oVEMP were recorded in all healthy patients. Mean and standard deviation for the first negative peak was 11.35±1.00 ms and for the first negative peak 16.30±1.10 ms. The mean amplitudes were 7.70±4.50 μV. The stability of n10 and p15 component was the same. AC oVEMP can be easy and fast obtained. N10 and p15 latencies may used as parameter for clinical interpretation. Amplitude fluctuations are relatively large. Results can be used in further clinical investigation of AC oVEMP. © Georg Thieme Verlag KG Stuttgart · New York.

Characterization of un-plasticized and propylene carbonate plasticized carboxymethyl cellulose doped ammonium chloride solid biopolymer electrolytes.

PubMed

Ahmad, N H; Isa, M I N

2016-02-10

Two solid biopolymer electrolytes (SBEs) systems of carboxymethyl cellulose doped ammonium chloride (CMC-AC) and propylene carbonate plasticized (CMC-AC-PC) were prepared via solution casting technique. The ionic conductivity of SBEs were analyzed using electrical impedance spectroscopy (EIS) in the frequency range of 50 Hz-1 MHz at ambient temperature (303K). The highest ionic conductivity of CMC-AC SBE is 1.43 × 10(-3)S/cm for 16 wt.% of AC while the highest conductivity of plasticized SBE system is 1.01 × 10(-2)S/cm when added with 8 wt.% of PC. TGA/DSC showed that the addition of PC had increased the decomposition temperature compared of CMC-AC SBE. Fourier transform infrared (FTIR) spectra showed the occurrence of complexation between the SBE components and it is proved successfully executed by Gaussian software. X-ray diffraction (XRD) indicated that amorphous nature of SBEs. It is believed that the PC is one of the most promising plasticizer to enhance the ionic conductivity and performance for SBE system. Copyright © 2015 Elsevier Ltd. All rights reserved.

Printing of highly conductive solution by alternating current electrohydrodynamic direct-write

NASA Astrophysics Data System (ADS)

Jiang, Jiaxin; Zheng, Gaofeng; Wang, Xiang; Zheng, Jianyi; Liu, Juan; Liu, Yifang; Li, Wenwang; Guo, Shumin

2018-03-01

Electrohydrodynamic Direct-Write (EDW) is a novel technology for the printing of micro/nano structures. In this paper, Alternating Current (AC) electrical field was introduced to improve the ejection stability of jet with highly conductive solution. By alternating the electrical field, the polarity of free charges on the surface of jet was changed and the average density of charge, as well as the repulsive force, was reduced to stabilize the jet. When the frequency of AC electrical field increased, the EDW process became more stable and the shape of deposited droplets became more regular. The diameter of printed droplets decreased and the deposition frequency increased with the increase of voltage frequency. The phenomenon of corona discharge was overcome effectively as well. To further evaluate the performance of AC EDW for highly conductive solution, more NaCl was added to the solution and the conductivity was increased to 2810μs/cm. With such high conductivity, the problem of serious corona discharge could still be prevented by AC EDW, and the diameter of printed droplets decreased significantly. This work provides an effective way to accelerate industrial applications of EDW.

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.%.

Unique dielectric dipole and hopping ion dipole relaxation in disordered systems

NASA Astrophysics Data System (ADS)

Govindaraj, G.

2018-04-01

Dielectric or ac conductivity measurements of dielectric and ion conducting glass and crystalline systems provide considerable insight into the nature of the dipolar and ionic motions in disordered solids. However, interpreting the dielectric or ac conductivity has been a matter of considerable debate based on the existing models and empirical formalism, particularly in regards to how best to represent the relaxation process that is the result of a transition from correlated to uncorrelated dipolar and ionic motions. A unique dipole interaction process has been proposed for the (a) dielectric dipole process (b) the hopping ion conducting dipole process and the (c) combination (a) and (b) for the description of dielectric spectra and ac conductivityspectra and results are reported.

Electrical and dielectric properties of PVdF-HFP - PMMA - (PC + DEC)- LiClO4 based gel polymer electrolyte

NASA Astrophysics Data System (ADS)

Gohel, Khushbu; Kanchan, D. K.; Maheshwaran, C.

2018-04-01

In the present paper, AC impedance studies have been measured to evaluate ion conduction behavior of (PVdF-HFP - PMMA) + (PC-DEC) + LiClO4 gel polymer electrolyte system prepared by solution casting method. Structural characterization and morphology has been carried out using XRD and SEM respectively. The AC conductivity and dielectric permittivity, electric modulus and relaxation mechanism have been studied. The variation of ac conductivity with frequency obeys Jonscher power law. Maximum value of dielectric constant ɛ' in the lower frequency region has been observed for the gel polymer electrolyte containing 7.5 wt% LiClO4. The highest conducting sample shows the shortest relaxation time.

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen, Z.; Hering, P.; Brown, S. B.

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.

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

DOE PAGES

Chen, Z.; Hering, P.; Brown, S. B.; ...

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.

Characterizing fiber-reinforced composite structures using AC-impedance spectroscopy (AC-IS)

NASA Astrophysics Data System (ADS)

Woo, Leta Y.

Property enhancement in composites depends largely on the reinforcement. For fiber-reinforced composites, the distribution of fibers is crucial in determining the electrical and mechanical performance. Image analysis methods for characterization can be time-consuming and/or destructive. This work explores the capability of AC-impedance spectroscopy (AC-IS), an electrical measurement technique, to serve as a rapid, non-destructive tool for characterizing composite microstructure. The composite requirements include a filler that is electrically conducting or semi-conducting with higher conductivity than the matrix, and a high-impedance interface or coating between the filler and the matrix. To establish an AC-IS characterization method, cement-matrix composites with steel reinforcement were employed as both a technologically important and a model system to investigate how fibers affect the electrical response. Beginning with spherical particulates and then fibers, composites were examined using composite theory and an "intrinsic conductivity" approach. The intrinsic conductivity approach applies to composites with low volume fractions of fibers (i.e., in the dilute regime) and relates how the composite conductivity varies relative to the matrix as a function of volume fraction. A universal equivalent circuit model was created to understand the AC-IS response of composites based on the geometry and volume fraction of the filler. Deviation from predicted behavior was assessed using a developed f-function, which quantifies how fibers contribute to the overall electrical response of the composite. Using the f-function, an AC-IS method for investigating fiber dispersion was established to characterize alignment, settling/segregation, and aggregation. Alignment was investigated using measurements made in three directions. A point-probe technique characterized settling and/or large-scale inhomogeneous mixing in samples. Aggregation was quantified using a "dispersion factor" that compared theoretical with measured values and served as an upper limit for how well the fibers were dispersed. The AC-IS method was then extended to two different cement-matrix composite systems, low resistivity fresh-paste cement composites (confirmed by time domain reflectometry) and high resistivity cement composites, both of which required additional analysis to apply the AC-IS characterization method.

Effect of the type of metal on the electrical conductivity and thermal properties of metal complexes: The relation between ionic radius of metal complexes and electrical conductivity

NASA Astrophysics Data System (ADS)

Morgan, Sh. M.; El-Ghamaz, N. A.; Diab, M. A.

2018-05-01

Co(II) complexes (1-4) and Ni(II) complexes (5-8) were prepared and characterized by elemental analysis, IR spectra and thermal analysis data. Thermal decomposition of all complexes was discussed using thermogravimetric analysis. The dielectric properties and alternating current conductivity were investigated in the frequency range 0.1-100 kHz and temperature range 300-660 K. The thermal activation energies of electrical conductivity (ΔE1 and ΔE2) values for complexes were calculated and discussed. The values of ΔE1 and ΔE2 for complexes (1-8) were found to decrease with increasing the frequency. Ac electrical conductivity (σac) values increases with increasing temperatures and the values of σac for Co(II) complexes are greater than Ni(II) complexes. Co(II) complexes showed a higher conductivity than other Ni(II) complexes due to the higher crystallinity as confirmed by X-ray diffraction analysis.

Electrical modulus and dielectric behavior of Cr3+ substituted Mg-Zn nanoferrites

NASA Astrophysics Data System (ADS)

Mansour, S. F.; Abdo, M. A.

2017-04-01

The dielectric parameters and ac electrical conductivity of Mg0.8Zn0.2CrxFe2-xO4; (0≤x≤0.025) nanoferrites synthesized citrate-nitrate auto-combustion method were studied using the complex impedance technique in the frequency and temperature ranges 4 Hz-5 MHz and 303-873 K respectively. Hopping of charge carriers plus interfacial polarization could interpret the behaviors of dielectric constant (ε‧), dielectric loss tangent (tanδ) and ac electrical conductivity (σac) with frequency, temperatures and composition. The up-normal behavior observed in tanδ trend with temperatures confirms the presence of relaxation loss (dipoles losses). Correlated barrier hopping (CBH) of electron is the conduction mechanism of the investigated nanoferrites. Cole-Cole plots at different temperatures emphasize the main role of grain and grain boundaries in the properties of the investigated nanoferrites. Cr3+ substitution can control the dielectric parameters and ac electrical conductivity of Mg-Zn nanoferrites making it candidates for versatile applications.

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.

Magnetic transit-time flowmeter

DOEpatents

Forster, George A.

1976-07-06

The flow rate of a conducting fluid in a stream is determined by disposing two permanent-magnet flowmeters in the stream, one downstream of the other. Flow of the conducting fluid causes the generation of both d-c and a-c electrical signals, the a-c comprising flow noise. Measurement of the time delay between similarities in the a-c signals by cross-correlation methods provides a measure of the rate of flow of the fluid.

Influence of Dzyaloshinskii-Moriya interaction and ballistic spin transport in the two and three-dimensional Heisenberg model

NASA Astrophysics Data System (ADS)

Lima, L. S.

2018-06-01

We study the effect of Dzyaloshisnkii-Moriya interaction on spin transport in the two and three-dimensional Heisenberg antiferromagnetic models in the square lattice and cubic lattice respectively. For the three-dimensional model, we obtain a large peak for the spin conductivity and therefore a finite AC conductivity. For the two-dimensional model, we have gotten the AC spin conductivity tending to the infinity at ω → 0 limit and a suave decreasing in the spin conductivity with increase of ω. We obtain a small influence of the Dzyaloshinskii-Moriya interaction on the spin conductivity in all cases analyzed.

Theoretical and experimental study of AC electrical conduction mechanism in the low temperature range of p-CuIn3Se5

NASA Astrophysics Data System (ADS)

Essaleh, L.; Amhil, S.; Wasim, S. M.; Marín, G.; Choukri, E.; Hajji, L.

2018-05-01

In the present work, an attempt has been made to study theoretically and experimentally the AC electrical conduction mechanism in disordered semiconducting materials. The key parameter considered in this analysis is the frequency exponent s(ω , T) =( ∂ln(σAC(ω , T))/∂ ln(ω)T , where σAC is the AC electrical conductivity that depends on angular frequency ω and temperature T. In the theoretical part of this work, the effect of the barrier hopping energy, the polaron radius and the characteristic relaxation time is considered. The theoretical models of Quantum Mechanical Tunneling (QMT), Non overlapping Small Polaron Tunneling (NSPT), Overlapping Large Polaron Tunneling (OLPT) and Correlated Barrier Hopping (CBH) are considered to fit experimental data of σAC in p-CuIn3Se5 (p-CIS135) in the low temperature range up to 96 K. Some important parameters, as the polaron radius, the localization length and the barrier hopping energies, are estimated and their temperature and frequency dependence discussed.

Electrical studies of D%AgI-(100-D)%[0.667Ag2O- 0.333{(0.4)B2O3-(0.6)TeO2}] fast ion conducting glasses

NASA Astrophysics Data System (ADS)

Kumar, E. Ramesh; Nageswar Rao, P.; Appa Rao, B.

2016-09-01

Super ion conducting glasses of composition D%AgI-(100-D)%[MAg2O-F{(F1)B2O3- (F2)TeO2}]; D=10.0 to 60.0 in steps of 10.0 for a fixed values of F1 (0.4), F2 (0.6) which are glass network formers, fixed values of modifier M(0.667), F (0.333) and D is dopant salt which was varied. These glasses were prepared by melt quenching technique. XRD spectra taken for all the samples. Electrical characterization was done in terms of AC and DC conductivities. DC and AC conductivities at room temperature increased from 10-5 to 10-1 scm-1 and DC activation energy (Edc) found to decrease from 0.36 to 0.19eV with increase in D% ratio. Measurements are performed over the frequency range 1 kHz to 3 MHz at different temperatures. From the impedance spectroscopy real and imaginary parts of impedances (Z', Z"), conductivities were calculated and plotted, and equivalent R-C circuit parameters were obtained from Cole-Cole plots. With the increase in D%, AC conductivity is observed to increase whereas the AC activation energy (Eac) is observed to decrease from 0.23 to 0.14 eV. The quantitative analysis of these results indicates that the electrical conductivity of silver borate glasses is enhanced with increase in D% ratio. Based on conductivity values these glasses are ionic conductors, in which conduction is by hopping mechanism. An attempt is made to understand the charge transportation process.

Electrical conductivity of activated carbon-metal oxide nanocomposites under compression: a comparison study.

PubMed

Barroso-Bogeat, A; Alexandre-Franco, M; Fernández-González, C; Macías-García, A; Gómez-Serrano, V

2014-12-07

From a granular commercial activated carbon (AC) and six metal oxide (Al2O3, Fe2O3, SnO2, TiO2, WO3 and ZnO) precursors, two series of AC-metal oxide nanocomposites were prepared by wet impregnation, oven-drying at 120 °C, and subsequent heat treatment at 200 or 850 °C in an inert atmosphere. Here, the electrical conductivity of the resulting products was studied under moderate compression. The influence of the applied pressure, sample volume, mechanical work, and density of the hybrid materials was thoroughly investigated. The DC electrical conductivity of the compressed samples was measured at room temperature by the four-probe method. Compaction assays suggest that the mechanical properties of the nanocomposites are largely determined by the carbon matrix. Both the decrease in volume and the increase in density were relatively small and only significant at pressures lower than 100 kPa for AC and most nanocomposites. In contrast, the bulk electrical conductivity of the hybrid materials was strongly influenced by the intrinsic conductivity, mean crystallite size, content and chemical nature of the supported phases, which ultimately depend on the metal oxide precursor and heat treatment temperature. The supported nanoparticles may be considered to act as electrical switches either hindering or favouring the effective electron transport between the AC cores of neighbouring composite particles in contact under compression. Conductivity values as a rule were lower for the nanocomposites than for the raw AC, all of them falling in the range of semiconductor materials. With the increase in heat treatment temperature, the trend is toward the improvement of conductivity due to the increase in the crystallite size and, in some cases, to the formation of metals in the elemental state and even metal carbides. The patterns of variation of the electrical conductivity with pressure and mechanical work were slightly similar, thus suggesting the predominance of the pressure effects rather than the volume ones.

ac conductivity in Gd doped Pb(Zr0.53Ti0.47)O3 ceramics

NASA Astrophysics Data System (ADS)

Portelles, J.; Almodovar, N. S.; Fuentes, J.; Raymond, O.; Heiras, J.; Siqueiros, J. M.

2008-10-01

This study is focused in the conduction processes taking place in 0.6 wt % Gd doped lead zirconate titanate samples PbZr0.53Ti0.47O3:Gd (PZT53/47:Gd) in the vicinity of the morphotropic phase boundary. Doped samples show very large dielectric permittivity with respect to that of undoped ones near the transition temperature. The frequency dependent ac conductivity of PZT53/47:Gd ceramics was studied in the 30-450 °C temperature range. X-ray diffraction analyses indicate the incorporation of Gd atoms to the structure. The changes in the dielectric properties as functions of temperature of the doped samples are taken as additional evidence of the incorporation of Gd into the crystal structure. Gd acts as donor center promoting extrinsic n-type conduction. The ac conductivity behavior obeys Jonscher universal relation in the 100 Hz-1 MHz frequency range for temperatures between 30 and 300 °C. The measured conductivity values for Gd doped PZT53/47 are higher than those of pure PZT53/47. According to the correlated barrier hopping model, the preponderant conduction mechanism in the frequency-temperature response was recognized as small polarons hopping mechanism.

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.

Dielectric behavior and AC conductivity of Cr doped α-Mn2O3

NASA Astrophysics Data System (ADS)

Chandra, Mohit; Yadav, Satish; Singh, K.

2018-05-01

The complex dielectric behavior of polycrystalline α-Mn2-xCrxO3 (x = 0.10) has been investigated isothermally at wide frequency range (4Hz-1 MHz) at different temperatures (300-390K). The dielectric spectroscopy results have been discussed in different formulism like dielectric constant, impedance and ac conductivity. The frequency dependent dielectric loss (tanδ) exhibit a clear relaxation behavior in the studied temperature range. The relaxation frequency increases with increasing temperature. These results are fitted using Arrhenius equation which suggest thermally activated process and the activation energy is 0.173±0.0024 eV. The normalized tanδ curves at different temperatures merge as a single master curve which indicate that the relaxation process follow the similar relaxation dynamics in the studied temperature range. Further, the dielectric relaxation follows non-Debye behavior. The impedance results inference that the grain boundary contribution dominate at lower frequency whereas grain contribution appeared at higher frequencies and exhibit strong temperature dependence. The ac conductivity data shows that the ac conductivity increases with increasing temperature which corroborate the semiconducting nature of the studied sample.

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

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 amore » 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.« less

Spectrophotometric and electrical properties of imperatorin: an organic molecule

NASA Astrophysics Data System (ADS)

Mir, Feroz A.

2015-09-01

Imperatorin (molecular formula = C16H14O4, molecular mass = 270) an organic molecule was isolated from ethyl acetate extract of the root parts of the plant Prangos pabularia. The optical study was carried out by ultraviolet-visible spectroscopy, and this compound showed an indirect allowed transition. The optical band gap ( E g ) was found around 3.75 eV. Photoluminescence shows various good emission bands. The frequency-dependent real part of the complex ac conductivity was found to follow the universal dielectric response: σ ac ( ω) α ω s [where σ ac ( ω) is the frequency-dependent total conductivity, ω is the frequency, and s is the frequency exponent]. From ac conductivity data analysis, correlated barrier hopping charge-transport mechanism is the dominant electrical transport process shown by this compound. The good emission, less absorption, wide band gap and good electrical properties shown by this compound project them as a bright choice for organic electronic devices.

Thermal, Structural, AC Conductivity, and Dielectric Properties of Ethyl-2-amino-6-ethyl-5-oxo-4-(3-phenoxyphenyl)-5,6-dihydro-4H-pyrano[3,2-c]quinoline-3-carboxylate Thin Films

NASA Astrophysics Data System (ADS)

El-Shabaan, M. M.

2018-05-01

Thermal, structural, alternating-current (AC) conductivity (σ AC), and dielectric properties of ethyl-2-amino-6-ethyl-5-oxo-4-(3-phenoxyphenyl)-5,6-dihydro-4H-pyrano[3,2-c]quinoline-3-carboxylate (HPQC) thin films have been studied. Thermogravimetry analysis and differential scanning calorimetry confirmed the thermal stability of HPQC over a wide temperature range. Fourier-transform infrared spectroscopy and x-ray diffraction analysis were carried out on HPQC in powder form and as-deposited thin film. The crystal system and space group type were determined for HPQC in powder form. The AC conductivity and dielectric properties were determined in the frequency range from 0.5 kHz to 5 MHz and temperature range from 296 K to 443 K. The AC electrical conduction of HPQC thin film was found to be governed by the small-polaron tunneling mechanism. The polaron hopping energy (W H), tunneling distance (R), and density of states (N) near the Fermi level were determined as functions of temperature and frequency. The dielectric properties of HPQC thin film were studied by analysis of Nyquist diagrams, the dissipation factor (tan δ), and real (ɛ') and imaginary (ɛ″) parts of the dielectric constant.

Vestibular Evoked Myogenic Potential Produced by Bone-Conducted Stimuli: A Study on its Basics and Clinical Applications in Patients with Conductive and Sensorineural Hearing Loss and a Group with Vestibular Schawannoma.

PubMed

Mahdi, Parvane; Amali, Amin; Pourbakht, Akram; Karimi Yazdi, Alireza; Bassam, Ali

2013-06-01

Vestibular evoked myogenic potential (VEMP) has recently been broadly studied in vestibular disorders. As it is evoked by loud sound stimulation, even mild conductive hearing loss may affect VEMP results. Bone-conducted (BC) stimulus is an alternative stimulation for evoking this response. This study aims to assess the characteristics of BC-VEMP in different groups of patients. We performed a cross sectional analysis on 20 healthy volunteers with normal pure-tone audiometry as a control group; and on a group of patients consisted of 20 participants with conductive hearing loss, five with bilateral sensorineural hearing loss and four with vestibular schawannoma. AC and BC-VEMP were performed in all participants. In control group the VEMP responses to both kinds of stimuli had an acceptable morphology and consisted of p13 and n23 waves. Latency value of these main components in each type of stimulus was not significantly different (P>0.05). However, the mean amplitude was larger in BC modality than AC stimulation (P=0.025). In the group with conductive hearing loss, the VEMP response was absent in fifteen (46.87%) of the 32 ears using the AC method, whereas all (100%) displayed positive elicitability of VEMP by BC method. Normal VEMP responses in both stimuli were evoked in all patients with sensorineural hearing loss. In patients with unilateral vestibular schwannomas (VS), 2 (50.00%) had neither AC-VEMP nor BC-VEMP. Auditory stimuli delivered by bone conduction can evoke VEMP response. These responses are of vestibular origin and can be used in vestibular evaluation of patients with conductive hearing loss.

Vestibular Evoked Myogenic Potential Produced by Bone-Conducted Stimuli: A Study on its Basics and Clinical Applications in Patients with Conductive and Sensorineural Hearing Loss and a Group with Vestibular Schawannoma

PubMed Central

Mahdi, Parvane; Amali, Amin; Pourbakht, Akram; Karimi Yazdi, Alireza; Bassam, Ali

2013-01-01

Introduction: Vestibular evoked myogenic potential (VEMP) has recently been broadly studied in vestibular disorders. As it is evoked by loud sound stimulation, even mild conductive hearing loss may affect VEMP results. Bone-conducted (BC) stimulus is an alternative stimulation for evoking this response. This study aims to assess the characteristics of BC-VEMP in different groups of patients. Materials and Methods: We performed a cross sectional analysis on 20 healthy volunteers with normal pure-tone audiometry as a control group; and on a group of patients consisted of 20 participants with conductive hearing loss, five with bilateral sensorineural hearing loss and four with vestibular schawannoma. AC and BC-VEMP were performed in all participants. Results: In control group the VEMP responses to both kinds of stimuli had an acceptable morphology and consisted of p13 and n23 waves. Latency value of these main components in each type of stimulus was not significantly different (P>0.05). However, the mean amplitude was larger in BC modality than AC stimulation (P=0.025). In the group with conductive hearing loss, the VEMP response was absent in fifteen (46.87%) of the 32 ears using the AC method, whereas all (100%) displayed positive elicitability of VEMP by BC method. Normal VEMP responses in both stimuli were evoked in all patients with sensorineural hearing loss. In patients with unilateral vestibular schwannomas (VS), 2 (50.00%) had neither AC-VEMP nor BC-VEMP. Conclusion: Auditory stimuli delivered by bone conduction can evoke VEMP response. These responses are of vestibular origin and can be used in vestibular evaluation of patients with conductive hearing loss. PMID:24303434

DC bias effect on alternating current electrical conductivity of poly(ethylene terephthalate)/alumina nanocomposites

NASA Astrophysics Data System (ADS)

Nikam, Pravin N.; Deshpande, Vineeta D.

2016-05-01

Polymer nanocomposites based on metal oxide (ceramic) nanoparticles are a new class of materials with unique properties and designed for various applications such as electronic device packaging, insulation, fabrication and automotive industries. Poly(ethylene terephthalate) (PET)/alumina (Al2O3) nanocomposites with filler content between 1 wt% and 5 wt% were prepared by melt compounding method using co-rotating twin screw extruder and characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and precision LCR meter techniques. The results revealed that proper uniform dispersion at lower content up to 2 wt% of nano-alumina observed by using TEM. Aggregation of nanoparticles was observed at higher content of alumina examined by using SEM and TEM. The frequency dependences of the alternating current (AC) conductivity (σAC) of PET/alumina nanocomposites on the filler content and DC bias were investigated in the frequency range of 20Hz - 1MHz. The results showed that the AC and direct current (DC) conductivity increases with increasing DC bias and nano-alumina content upto 3 wt%. It follows the Jonscher's universal power law of solids. It revealed that σAC of PET/alumina nanocomposites can be well characterized by the DC conductivity (σDC), critical frequency (ωc), critical exponent of the power law (s). Roll of DC bias potential led to an increase of DC conductivity (σDC) due to the creation of additional conducting paths with the polymer nanocomposites and percolation behavior achieved through co-continuous morphology.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bouziane, M.; Taibi, M., E-mail: taibiens@yahoo.fr; Boukhari, A.

Electrical properties of Pb{sub 2}Na{sub 0.8}Eu{sub 0.2}Nb{sub 4.8}Fe{sub 0.2}O{sub 15} tungsten bronze compound were investigated. Ferroelectric phase transition of diffuse type is observed at 395 °C. Conductivity study as a function of temperature (RT-600 °C) and at three different frequencies (10, 100 and 1000 kHz) suggests the existence of dominant ionic conduction. The rise of ac conductivity on increasing temperature supports the NTCR (negative temperature coefficient of resistance) behaviour of the material. The activation energies have been evaluated from ac conductivity using Arrhenius equation and discussed. Different conduction mechanisms were identified. For comparison, the conducting properties of Pb{sub 2}Na{sub 0.8}R{submore » 0.2}Nb{sub 4.8}Fe{sub 0.2}O{sub 15} (R=Dy, Nd, La) were also investigated. - Graphical abstract: Thermal evolution of lnσ{sub ac} of Pb{sub 2}Na{sub 0.8}Eu{sub 0.2}Nb{sub 4.8}Fe{sub 0.2}O{sub 15} at selected frequencies. Display Omitted - Highlights: • We found that TB compounds exhibit a diffuse type of first- order transition. • A negative temperature coefficient of resistance (NTCR) behaviour is observed. • Three conduction mechanisms were identified: n-and/or p-type at low temperatures. • The conduction mechanism in the studied compounds is very complex.« less

Dielectric properties and electrical conductivity of the hybrid organic-inorganic polyvanadates (H{sub 3}N(CH{sub 2}){sub 4}NH{sub 3})[V{sub 6}O{sub 14}

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nefzi, H.; Sediri, F., E-mail: faouzi.sediri@ipeit.rnu.tn; Faculte des Sciences de Tunis, Universite Tunis El Manar, 2092 El Manar, BP 94 CEDEX 1068, Cite Rommana Tunis

2012-06-15

Plate-like crystals of the polyvanadate (H{sub 3}N(CH{sub 2}){sub 4}NH{sub 3})[V{sub 6}O{sub 14}] have been synthesized via an hydrothermal treatment. X-ray powder diffraction, scanning electron microscope, Fourier transform infrared spectroscopy, electron spin resonance and complex impedance spectroscopy were used to analyze the hybrid material. The frequency dependence of AC conductivity at different temperatures indicates that the CBH model is the probable mechanism for the AC conduction behavior. The conductivity was measured by complex impedance spectroscopy which is equal to 31.10{sup -3} {Omega}{sup -1} m{sup -1} at 443 K. The Arrhenius diagram is not linear, it presents a rupture situated at 357more » K and the activation energies' average values are 0.22 eV and 0.14 eV, deduced from the Arrhenius relation. - Graphical abstract: At high temperature {epsilon} Double-Prime increases more rapidly which is due to the increasing conduction loss which rises with the increment in the DC conductivity. Highlights: Black-Right-Pointing-Pointer Rectangular plate-like crystals (H{sub 3}N(CH{sub 2}){sub 4}NH{sub 3})[V{sub 6}O{sub 14}] were synthesized. Black-Right-Pointing-Pointer frequency and temperature dependence of AC conductivity indicate CBH model. Black-Right-Pointing-Pointer The temperature dependence of DC conductivity exhibits two conduction mechanisms.« less

40 CFR 86.1773-99 - Test sequence; general requirements.

Code of Federal Regulations, 2011 CFR

2011-07-01

... test simulation procedures, AC1 and AC2, for the 2001 to 2003 model years only. If a manufacturer desires to conduct an alternative SC03 test simulation other than AC1 and AC2, or the AC1 and AC2 simulations for the 2004 and subsequent model years, the simulation test procedure must be approved in advance...

40 CFR 86.1773-99 - Test sequence; general requirements.

Code of Federal Regulations, 2013 CFR

2013-07-01

... test simulation procedures, AC1 and AC2, for the 2001 to 2003 model years only. If a manufacturer desires to conduct an alternative SC03 test simulation other than AC1 and AC2, or the AC1 and AC2 simulations for the 2004 and subsequent model years, the simulation test procedure must be approved in advance...

40 CFR 86.1773-99 - Test sequence; general requirements.

Code of Federal Regulations, 2012 CFR

2012-07-01

... test simulation procedures, AC1 and AC2, for the 2001 to 2003 model years only. If a manufacturer desires to conduct an alternative SC03 test simulation other than AC1 and AC2, or the AC1 and AC2 simulations for the 2004 and subsequent model years, the simulation test procedure must be approved in advance...

Dielectric spectroscopy investigation of proton transfer processes in carboxymethyl alpha-cyclodextrin polymer cross-linked by epichlorohydrin

NASA Astrophysics Data System (ADS)

Papaioannou, Panagoula K.; Karagianni, Chaido S.; Kakali, Glykeria; Charalampopoulos, Vasileios G.

2018-03-01

The carboxymethyl-α-cyclodextrin polymer (cross-linked by epichlorohydrin) is investigated by dielectric spectroscopy over a frequency range of 0.1-100 kHz and the temperature ranges of 137.2-297.6 K (cooling) and 137.2-472 K (heating). Upon cooling to 288.1 K, the ac-conductivity invariance is attributed to slight changes in the topology of the H-bonded chains. From 288.1 to 244.0 K, the ac-conductivity decreases abruptly (following the Arrhenius law with Eα = 0.40 eV), whereas below 244.0 K it presents no important variations. During heating from 137.2 to 302.6 K, no thermal hysteresis is observed. From 302.6 to 364.9 K, the ac-conductivity increases (Eα = 0.71 eV), whereas above 383 K it decreases up to 436.7 K since the dehydration process has been completed and the H-bonded chains can no longer be retained. From 436.7 to 472 K, the ac-conductivity increases again (Eα = 0.76 eV) indicating the formation of "new" H-bonded chains. Curve fitting of various relaxation processes is done by Havriliak-Negami equation at selective temperatures.

Dielectric relaxation dynamics and AC conductivity scaling of metal-organic framework (MOF-5) based polymer electrolyte nanocomposites incorporated with ionic liquid

NASA Astrophysics Data System (ADS)

Dutta, Rituraj; Kumar, A.

2017-10-01

Dielectric relaxation dynamics and AC conductivity scaling of a metal-organic framework (MOF-5) based poly (vinylidene fluoride-co-hexafluoropropylene) (PVdf-HFP) incorporated with 1-Butyl-3-methylimidazolium hexafluorophosphate have been studied over a frequency range of 40 Hz-5 MHz and in the temperature range of 300 K-380 K. High values of dielectric permittivity (~{{\\varepsilon }\\prime} ) having strong dispersion are obtained at low frequency because of interfacial polarization. The real part of the dielectric modulus spectra (M‧) shows no prominent peak, whereas the imaginary part (M″) shows certain peaks, with a reduction in relaxation time (τ) that can be attributed to a non-Debye relaxation mechanism. The spectra also depict both concentration- and temperature-independent scaling behavior. The power law dependent variation of AC conductivity follows the jump relaxation model and reveals activated ion hopping over diffusion barriers. The value of the frequency exponent is observed to decrease with increasing concentration of ionic liquid, indicating the forward hopping of ions in the relaxation process. The AC conductivity scaling curves at different temperatures also depict the temperature-independent relaxation dynamics.

Enhanced Corrosion Resistance and Interfacial Conductivity of TiC x/a-C Nanolayered Coatings via Synergy of Substrate Bias Voltage for Bipolar Plates Applications in PEMFCs.

PubMed

Yi, Peiyun; Zhang, Weixin; Bi, Feifei; Peng, Linfa; Lai, Xinmin

2018-06-06

Proton-exchange membrane fuel cells are one kind of renewable and clean energy conversion device, whose metallic bipolar plates are one of the key components. However, high interfacial contact resistance and poor corrosion resistance are still great challenges for the commercialization of metallic bipolar plates. In this study, we demonstrated a novel strategy for depositing TiC x /amorphous carbon (a-C) nanolayered coatings by synergy of 60 and 300 V bias voltage to enhance corrosion resistance and interfacial conductivity. The synergistic effects of bias voltage on the composition, microstructure, surface roughness, electrochemical corrosion behaviors, and interfacial conductivity of TiC x /a-C coatings were explored. The results revealed that the columnar structures in the inner layer were suppressed and the surface became rougher with the 300 V a-C layer outside. The composition analysis indicated that the sp 2 content increased with an increase of 300 V sputtering time. Due to the synergy strategy of bias voltage, lower corrosion current densities were achieved both in potentiostatic polarization (1.6 V vs standard hydrogen electrode) and potentiodynamic polarization. With the increase of 300 V sputtering time, the interfacial conductivity was improved. The enhanced corrosion resistance and interfacial conductivity of the TiC x /a-C coatings would provide new opportunities for commercial bipolar plates.

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.

LASER BIOLOGY AND MEDICINE: Effect of repetitive laser pulses on the electrical conductivity of intervertebral disc tissue

NASA Astrophysics Data System (ADS)

Omel'chenko, A. I.; Sobol', E. N.

2009-03-01

The thermomechanical effect of 1.56-μm 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.

Contribution of Vestibular-Evoked Myogenic Potential (VEMP) testing in the assessment and the differential diagnosis of otosclerosis

PubMed Central

Tramontani, Ourania; Gkoritsa, Eleni; Ferekidis, Eleftherios; Korres, Stavros G.

2014-01-01

Background The aim of this prospective clinical study was to evaluate the clinical importance of Vestibular-Evoked Myogenic Potentials (VEMPs) in the assessment and differential diagnosis of otosclerosis and otologic diseases characterized by “pseudo-conductive” components. We also investigated the clinical appearance of balance disorders in patients with otosclerosis by correlating VEMP results with the findings of caloric testing and pure tone audiometry(PTA). Material/Methods Air-conducted(AC) 4-PTA, bone-conducted(BC) 4-PTA, air-bone Gap(ABG), AC, BC tone burst evoked VEMP, and calorics were measured preoperatively in 126 otosclerotic ears. Results The response rate of the AC-VEMPs and BC-VEMPs was 29.36% and 44.03%, respectively. Statistical differences were found between the means of ABG, AC 4-PTA, and BC 4-PTA in the otosclerotic ears in relation to AC-VEMP elicitability. About one-third of patients presented with disequilibrium. A statistically significant interaction was found between calorics and dizziness in relation to PTA thresholds. No relationship was found between calorics and dizziness with VEMPs responses. Conclusions AC and BC VEMPs can be elicited in ears with otosclerosis. AC-VEMP is more vulnerable to conductive hearing loss. Evaluation of AC-VEMP thresholds can be added in the diagnostic work-up of otosclerosis in case of doubt, enhancing differential diagnosis in patients with air-bone gaps. Otosclerosis is not a cause of canal paresis or vertigo. PMID:24509900

AC transport in p-Ge/GeSi quantum well in high magnetic fields

DOE Office of Scientific and Technical Information (OSTI.GOV)

Drichko, I. L.; Malysh, V. A.; Smirnov, I. Yu.

2014-08-20

The contactless surface acoustic wave technique is implemented to probe the high-frequency conductivity of a high-mobility p-Ge/GeSi quantum well structure in the regime of integer quantum Hall effect (IQHE) at temperatures 0.3–5.8 K and magnetic fields up to 18 T. It is shown that, in the IQHE regime at the minima of conductivity, holes are localized and ac conductivity is of hopping nature and can be described within the “two-site” model. The analysis of the temperature and magnetic-field-orientation dependence of the ac conductivity at odd filing factors enables us to determine the effective hole g-factor, |g{sub zz}|≈4.5. It is shownmore » that the in-plane component of the magnetic field leads to a decrease in the g-factor as well as increase in the cyclotron mass, which is explained by orbital effects in the complex valence band of germanium.« less

[Air conducted ocular VEMP: II. First clinical investigations].

PubMed

Walther, L E; Schaaf, H; Sommer, D; Hörmann, K

2011-10-01

Vestibular-evoked myogenic potentials (VEMP) are widely used to assess vestibular function. Air conducted (AC) cervical VEMP (cVEMP) reflect sacculus and inferior vestibular nerve function. Ocular VEMP (oVEMP) however has been hardly examined up to now. In recent studies it has been assumed that AC oVEMP probably reflects superior vestibular nerve function. The aim of this pilot study was to evaluate clinical application of the AC oVEMP. AC oVEMP were recorded in patients with peripheral vestibular disorders (n=21). In addition thermal irritation and head impulse test were performed and AC cVEMP were recorded. For intense AC-sound stimulation tone bursts (500 Hz) with 100 dB nHL were used. In peripheral vestibular disorders AC oVEMP and AC cVEMP could be classified into: • type 1 (inferior vestibular neuritis) with loss of AC oVEMP but normal AC cVEMP, • type 2, probable type of superior vestibular neuritis, showing present AC cVEMP but loss of AC oVEMP, • type 3, probable complete vestibular neuritis, without AC oVEMP and AC cVEMP. AC oVEMP may be used as an appropriate test for clinical investigation in patients with vestibular disorders. AC oVEMP is an additional, essential test for assessing otolith function beside AC cVEMP. Further vestibular test are necessary for precise clinical interpretation. © Georg Thieme Verlag KG Stuttgart · New York.

DC bias effect on alternating current electrical conductivity of poly(ethylene terephthalate)/alumina nanocomposites

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nikam, Pravin N., E-mail: pravinya26@gmail.com; Deshpande, Vineeta D., E-mail: drdeshpandevd@gmail.com

Polymer nanocomposites based on metal oxide (ceramic) nanoparticles are a new class of materials with unique properties and designed for various applications such as electronic device packaging, insulation, fabrication and automotive industries. Poly(ethylene terephthalate) (PET)/alumina (Al{sub 2}O{sub 3}) nanocomposites with filler content between 1 wt% and 5 wt% were prepared by melt compounding method using co-rotating twin screw extruder and characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and precision LCR meter techniques. The results revealed that proper uniform dispersion at lower content up to 2 wt% of nano-alumina observed by using TEM. Aggregation of nanoparticles was observedmore » at higher content of alumina examined by using SEM and TEM. The frequency dependences of the alternating current (AC) conductivity (σ{sub AC}) of PET/alumina nanocomposites on the filler content and DC bias were investigated in the frequency range of 20Hz - 1MHz. The results showed that the AC and direct current (DC) conductivity increases with increasing DC bias and nano-alumina content upto 3 wt%. It follows the Jonscher’s universal power law of solids. It revealed that σ{sub AC} of PET/alumina nanocomposites can be well characterized by the DC conductivity (σ{sub DC}), critical frequency (ω{sub c}), critical exponent of the power law (s). Roll of DC bias potential led to an increase of DC conductivity (σ{sub DC}) due to the creation of additional conducting paths with the polymer nanocomposites and percolation behavior achieved through co-continuous morphology.« less

Differences between direct current and alternating current capacitance nonlinearities in high-k dielectrics and their relation to hopping conduction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Khaldi, O.; Kassmi, M.; El Manar University, LMOP, 2092 Tunis

2014-08-28

Capacitance nonlinearities were studied in atomic layer deposited HfO{sub 2} films using two types of signals: a pure ac voltage of large magnitude (ac nonlinearities) and a small ac voltage superimposed to a large dc voltage (dc nonlinearities). In theory, ac and dc nonlinearities should be of the same order of magnitude. However, in practice, ac nonlinearities are found to be an order of magnitude higher than dc nonlinearities. Besides capacitance nonlinearities, hopping conduction is studied using low-frequency impedance measurements and is discussed through the correlated barrier hopping model. The link between hopping and nonlinearity is established. The ac nonlinearitiesmore » are ascribed to the polarization of isolated defect pairs, while dc nonlinearities are attributed to electrode polarization which originates from defect percolation paths. Both the ac and dc capacitance nonlinearities display an exponential variation with voltage, which results from field-induced lowering of the hopping barrier energy.« less

Self-consistent modeling of terahertz waveguide and cavity with frequency-dependent conductivity

DOE Office of Scientific and Technical Information (OSTI.GOV)

Huang, Y. J.; Chu, K. R., E-mail: krchu@yahoo.com.tw; Thumm, M.

The surface resistance of metals, and hence the Ohmic dissipation per unit area, scales with the square root of the frequency of an incident electromagnetic wave. As is well recognized, this can lead to excessive wall losses at terahertz (THz) frequencies. On the other hand, high-frequency oscillatory motion of conduction electrons tends to mitigate the collisional damping. As a result, the classical theory predicts that metals behave more like a transparent medium at frequencies above the ultraviolet. Such a behavior difference is inherent in the AC conductivity, a frequency-dependent complex quantity commonly used to treat electromagnetics of metals at opticalmore » frequencies. The THz region falls in the gap between microwave and optical frequencies. However, metals are still commonly modeled by the DC conductivity in currently active vacuum electronics research aimed at the development of high-power THz sources (notably the gyrotron), although a small reduction of the DC conductivity due to surface roughness is sometimes included. In this study, we present a self-consistent modeling of the gyrotron interaction structures (a metallic waveguide or cavity) with the AC conductivity. The resulting waveguide attenuation constants and cavity quality factors are compared with those of the DC-conductivity model. The reduction in Ohmic losses under the AC-conductivity model is shown to be increasingly significant as the frequency reaches deeper into the THz region. Such effects are of considerable importance to THz gyrotrons for which the minimization of Ohmic losses constitutes a major design consideration.« less

Impurities or a neutral Fermi surface? A further examination of the low-energy ac optical conductivity of SmB6

NASA Astrophysics Data System (ADS)

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

2018-05-01

Recent experiments have uncovered evidence of low energy excitations in the bulk of SmB6 that are perhaps associated with unconventional quasiparticles, bringing into question whether this Kondo "insulator" is truly insulating in the bulk. Recently, we demonstrated that SmB6 possesses significant in-gap bulk ac conduction far in excess of typical disordered semiconductors. Whether such conduction is an intrinsic feature of SmB6, suggesting the formation of an exotic state, or residual conduction from impurities continues to be a topic of debate. Here, we further examine the origin of the ac optical conductivity of SmB6 in light of recent experimental and theoretical developments. The optical conductivity of SmB6 is shown to possess distinct regimes of either dominant free carrier or localized response contributions. The free carrier response is found to be in good qualitative agreement with previous literature, although quantitative differences are revealed and discussed. The localized response, which dominates at the lowest temperatures, is analyzed in the context of models of either in-gap impurity states or an exotic neutral Fermi surface. The charge density or effective mass of this low temperature in-gap conductivity is extracted through a conductivity sum rule analysis and found to be in general alignment with both models in the appropriate limits. Our results shed further light on the nature of the in-gap states of SmB6.

Ac conductivity and dielectric properties of bulk tin phthalocyanine dichloride (SnPcCl 2)

NASA Astrophysics Data System (ADS)

El-Nahass, M. M.; Farid, A. M.; Abd El-Rahman, K. F.; Ali, H. A. M.

2008-07-01

The ac conductivity, σac( ω), has been measured for bulk tin phthalocyanine dichloride (SnPcCl 2) in the form of compressed pellet with evaporated ohmic Au electrodes in a temperature range 303-403 K. Ac conductivity, σac( ω), is found to vary as ωs in the frequency range 42 Hz-5×10 6 Hz. At low range of frequency, s<1 and it decreases with the increase in temperature indicating a dominant hopping process. At high range of frequency, s is found to be equal to ≈1.09 and is temperature independent. The dielectric constant, ε1, and dialectic loss, ε2, have been determined for bulk SnPcCl 2. Both ε1 and ε2 decrease with the increase in frequency and increase with the increase in temperature. The Cole-Cole types have been used to determine some parameters such as; the macroscopic relaxation time ( τo), the molecular relaxation time ( τ), the activation energy for relaxation ( Eo) and the distribution parameter ( α). The temperature dependence of τ is expressed by a thermally activated process with the activation energy of 0.299 eV.

AC electrical conductivity and dielectric relaxation studies on n-type organic thin films of N, N‧-Dimethyl-3,4,9,10-perylenedicarboximide (DMPDC)

NASA Astrophysics Data System (ADS)

Qashou, Saleem I.; Darwish, A. A. A.; Rashad, M.; Khattari, Z.

2017-11-01

Both Alternating current (AC) conductivity and dielectric behavior of n-type organic thin films of N, N‧-Dimethyl-3,4,9,10-perylenedicarboximide (DMPDC) have been investigated. Fourier transformation infrared (FTIR) spectroscopy is used for identifying both powder and film bonds which confirm that there are no observed changes in the bonds between the DMPDC powder and evaporated films. The dependence of AC conductivity on the temperature for DMPDC evaporated films was explained by the correlated barrier hopping (CBH) model. The calculated barrier height using CBH model shows a decreasing behavior with increasing temperature. The mechanism of dielectric relaxation was interpreted on the basis of the modulus of the complex dielectric. The calculated activation energy of the relaxation process was found to be 0.055 eV.

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.

Alternate current conductivity in BSb films prepared by PLD technique: Electron transport processes in low-temperature range (10-275 K)

NASA Astrophysics Data System (ADS)

Das, Shirsendu; Bhunia, Ritamay; Hussain, Shamima; Bhar, Radhaballabh; Kumar Pal, Arun

2017-04-01

This study is focused on the measurement of alternate current (a.c.) electrical conductivity of BSb films, deposited on fluorine-doped tin oxide (FTO)-coated glass substrates at 673K by the pulsed laser deposition (PLD) technique. The frequency-dependent a.c. conductivity is measured as a function of temperature (10-275K) and frequency (100Hz-100kHz). The transport processes governing the electrical conduction processes in this material are analyzed critically. It is observed from FESEM micrograph that the film is composed of small discrete grain with sizes varying in the range 6-12nm. It is interesting to notice from \\lnσ_ac versus 1000/T plot that there are three distinct zones: i) Semiconductor zone at high temperature from 275 to 150K, ii) Insulator zone at low temperature from 70 to 10K and iii) an abrupt change of the \\lnσ_ac versus 1000/T plot at ˜ 75 indicating MIS transition occurring in this BSb film. We found that the activation energy for the BSb films in the lower-temperature range was quite low ˜ 6 to 41neV, while that in the higher-temperature range was 20 to 50meV.

AC impedance investigations of proton conduction in Nafion(sup TM)

NASA Astrophysics Data System (ADS)

Cahan, B. D.; Wainright, J. S.

1993-12-01

AC impedance spectroscopy has been employed to study the conduction of protons in Nafion 117 polymer electrolyte membrane. Both two- and four-electrode geometries have been used to uniquely distinguish between the membrane impedance and the interfacial impedances. The results show that the impedance of Nafion for frequencies up to 100 kHz is characterized by a pure resistance, similar to conventional liquid electrolytes. The frequency dependent features observed using a two-electrode geometry are shown to be consistent will well-characterized interfacial impedances and do not arise from ionic conduction in the membrane. These results show that previous two-electrode studies reported in the literature have misinterpreted the impedance of the electrode interfaces as belonging to the conduction process in the electrolyte.

Communication: Dimensionality of the ionic conduction pathways in glass and the mixed-alkali effect.

PubMed

Novy, Melissa; Avila-Paredes, Hugo; Kim, Sangtae; Sen, Sabyasachi

2015-12-28

A revised empirical relationship between the power law exponent of ac conductivity dispersion and the dimensionality of the ionic conduction pathway is established on the basis of electrical impedance spectroscopic (EIS) measurements on crystalline ionic conductors. These results imply that the "universal" ac conductivity dispersion observed in glassy solids is associated with ionic transport along fractal pathways. EIS measurements on single-alkali glasses indicate that the dimensionality of this pathway D is ∼2.5, while in mixed-alkali glasses, D is lower and goes through a minimum value of ∼2.2 when the concentrations of the two alkalis become equal. D and σ display similar variation with alkali composition, thus suggesting a topological origin of the mixed-alkali effect.

Ocular vestibular evoked myogenic potential elicited from binaural air-conducted stimulations: clinical feasibility in patients with peripheral vestibular dysfunction.

PubMed

Iwasaki, Shinichi; Egami, Naoya; Inoue, Aki; Kinoshita, Makoto; Fujimoto, Chisato; Murofushi, Toshihisa; Yamasoba, Tatsuya

2013-07-01

Ocular vestibular evoked myogenic potentials (oVEMPs) to binaural air-conducted stimulation (ACS) may provide a convenient way of assessing the crossed vestibulo-ocular reflex in patients with vestibular dysfunction as well as in healthy subjects. To investigate the clinical feasibility of using oVEMPs in response to binaural ACS to assess normal subjects and patients with vestibular dysfunction. The study investigated 24 normal subjects (14 men and 10 women, aged from 23 to 60 years) and 14 patients with unilateral peripheral vestibular dysfunction. Each subject underwent oVEMP testing in response to monaural ACS and binaural ACS (500 Hz tone burst, 135 dBSPL). In normal subjects, bilateral oVEMPs were elicited in 75% of subjects in response to monaural ACS and in 91% in response to binaural ACS. Asymmetry ratios (ARs) of the responses to binaural ACS were significantly smaller than those of the responses to monaural ACS (p < 0.01). In patients with unilateral vestibular dysfunction, there were no significant differences in the amplitude, latency, or AR of the responses between monaural and binaural ACS. Approximately 30% of patients showed reduced ARs to binaural ACS relative to monaural ACS, primarily due to contamination by uncrossed responses elicited in healthy ears.

Thermal and ac electrical properties of N-methylanthranilic acid below room temperature

NASA Astrophysics Data System (ADS)

Abdel-Kader, M. M.; Basha, M. A. F.; Ramzy, G. H.; Aboud, A. I.

2018-06-01

In this study, we investigated the thermal and alternating current (ac) electrical properties of N-methylanthranilic acid. Based on data obtained by differential scanning calorimetry, we detected two endothermic transitions at ≈ 213 K and ≈265.41 K. The weakening of hydrogen bonds as the temperature increased appeared to be the main cause of these phase transitions. We also recorded the melting point at about 475.5 K. Both the ac conductivity (σac) and complex dielectric constant (ε∗ = ε ' - jε ' ') were studied as functions of temperature over the frequency range from 1 kHz to 100 kHz. We observed significant variations in the thermal and electrical properties before and after the transition temperature at 265.41 K. The conduction mechanism responsible for the ac electrical properties before this transition was due to overlapping large polarons. These novel results are expected to have impacts on the application of organic semiconductors and dielectrics.

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hemalatha, K. S.; Damle, R.; Rukmani, K., E-mail: rukmani9909@yahoo.co.in

2015-10-21

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

Schlieren optical visualization for transient EHD induced flow in a stratified dielectric liquid under gas-phase ac corona discharges

NASA Astrophysics Data System (ADS)

Ohyama, R.; Inoue, K.; Chang, J. S.

2007-01-01

A flow pattern characterization of electrohydrodynamically (EHD) induced flow phenomena of a stratified dielectric fluid situated in an ac corona discharge field is conducted by a Schlieren optical system. A high voltage application to a needle-plate electrode arrangement in gas-phase normally initiates a conductive type EHD gas flow. Although the EHD gas flow motion initiated from the corona discharge electrode has been well known as corona wind, no comprehensive study has been conducted for an EHD fluid flow motion of the stratified dielectric liquid that is exposed to the gas-phase ac corona discharge. The experimentally observed result clearly presents the liquid-phase EHD flow phenomenon induced from the gas-phase EHD flow via an interfacial momentum transfer. The flow phenomenon is also discussed in terms of the gas-phase EHD number under the reduced gas pressure (reduced interfacial momentum transfer) conditions.

Infrared conductivity of cuprates using Yang-Rice-Zhang ansatz: Review of our recent investigations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Singh, Navinder; Sharma, Raman

2015-05-15

A review of our recent investigations related to the ac transport properties in the psedogapped state of cuprate high temperature superconductors is presented. For our theoretical calculations we use a phenomenological Green’s function proposed by Yang, Rice and Zhang (YRZ). This is based upon the renormalized mean-field theory of the Hubbard model and takes into account the strong electron-electron interaction present in Cuprates. The pseudogap is also taken into account through a proposed self energy. We have tested the form of the Green’s function by computing ac conductivity of cuprates and then compared with experimental results. We found agreement betweenmore » theory and experiment in reproducing the doping evolution of ac conductivity but there is a problem with absolute magnitudes and their frequency dependence. This shows a partial success of the YRZ ansatz. The ways to rectify it are suggested and worked out.« less

Impedance and AC conductivity studies of Sm3+ substituted 0.8Ba0.2(Bi0.5K0.5)TiO3 lead free ceramics

NASA Astrophysics Data System (ADS)

Sastry, C. V. S. S.; Ramesh, M. N. V.; Ramesh, K. V.

2017-07-01

Samarium substituted 0.8Ba0.2(Bi0.5K0.5)TiO3 (here after abbreviated as BTBKT-20) lead free ceramics with composition 0.8Ba0.2(Bi0.5(1-x)Sm0.5xK0.5)TiO3 (where x=0.01,0.03,0.05) lead free ceramics have been prepared by solid state reaction and followed by high energy ball milling process. The present paper focuses the impedance and ac conductivity studies of Sm substituted BTBKT-20 lead free ceramics. Impedance spectroscopic studies revealthat temperature dependent relaxation process. Single depressed semi circle was observed in Cole-Cole plots, indicates non-Debye kind of relaxation process. Maximum grain resistance was observed for x=0.03 Sm substituted BTBKT-20 sample. Frequency and temperature dependent AC conductivity was calculated and it found to obey the universal Jonscher's power law and the values of activation energies suggest that conduction is ionic in nature.

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.

Electromagnetic augmentation for casting of thin metal sheets

DOEpatents

Hull, J.R.

1987-10-28

Thin metal sheets are cast by magnetically levitating molten metal deposited in a model within a ferromagnetic yoke and between AC conducting coils and linearly displacing the magnetically levitated liquid metal while it is being cooled by the water-cooled walls of the mold to form a solid metal sheet. A conducting shield is electrically coupled to the molten metal sheet to provide a return path for eddy currents induced in the metal sheet by the current in the AC conducting coils. In another embodiment, a DC conducting coil is coupled to the metal sheet for providing a direct current therein which interacts with the magnetic field to levitate the moving metal sheet. Levitation of the metal sheet in both molten and solid forms reduces its contact pressure with the mold walls while maintaining sufficient engagement therebetween to permit efficient conductive cooling by the mold through which a coolant fluid may be circulated. 8 figs.

Electrode effects in dielectric spectroscopy measurements on (Nb+In) co-doped TiO2

NASA Astrophysics Data System (ADS)

Crandles, D. A.; Yee, S. M. M.; Savinov, M.; Nuzhnyy, D.; Petzelt, J.; Kamba, S.; Prokeš, J.

2016-04-01

Recently, several papers reported the discovery of giant permittivity and low dielectric loss in (Nb+In) co-doped TiO2. A series of tests was performed which included the measurement of the frequency dependence of the dielectric permittivity and alternating current (ac) conductivity of co-doped (Nb+In)TiO2 as a function of electrode type, sample thickness, and temperature. The data suggest that the measurements are strongly affected by the electrodes. The consistency between four-contact van der Pauw direct current conductivity measurements and bulk conductivity values extracted from two-contact ac conductivity measurements suggest that the values of colossal permittivity are, at least in part, a result of Schottky barrier depletion widths that depend on electrode type and temperature.

Electrode effects in dielectric spectroscopy measurements on (Nb +In) co-doped TiO2

NASA Astrophysics Data System (ADS)

Crandles, David; Yee, Susan; Savinov, Maxim; Nuzhnyy, Dimitri; Petzelt, Jan; Kamba, Stanislav; Prokes, Jan

Recently, several papers reported the discovery of giant permittivity and low dielectric loss in (Nb+In) co-doped TiO2. A series of tests was performed which included the measurement of the frequency dependence of the dielectric permittivity and ac conductivity of co-doped (Nb+In)TiO2 as a function of electrode type, sample thickness and temperature. The data suggest that the measurements are strongly affected by the electrodes. The consistency between four contact van der Pauw dc conductivity measurements and bulk conductivity values extracted from two contact ac conductivity measurements suggest that the values of colossal permittivity are, at least in part, a result of Schottky barrier depletion widths that depend on electrode type and temperature. Nserc, Czech Science Foundation (Project 15-08389S).

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.

AC conductivity studies of La doped Ba0.5Sr0.5TiO3

NASA Astrophysics Data System (ADS)

D'Souza, Slavia Deeksha; Rohith, Kotla Surya; Bhatnagar, Anil K.; Kumar, A. Sendil

2017-05-01

Ferroelectric material with high dielectric constant of Ba0.5Sr0.5TiO3 is synthesized through Solid State Reaction and fraction of Lanthanum is substituted to introduce hole concentration. XRay Diffraction shows all the samples are stabilized in cubic crystal structure. With La doped samples the Cole-Cole plot is modified and AC conductivity increases at higher temperatures as well as higher frequencies compared to undoped sample.

Electrical screening procedure for solid ionic conductors

NASA Technical Reports Server (NTRS)

Kautz, H. E.; Singer, J.; Fielder, W. L.; Fordyce, J. S.

1973-01-01

An electrical screening method has been developed for preliminary evaluation of polycrystalline specimens of candidates for use as solid ionic conductive electrolytes in batteries. The procedure measures dielectric loss and capacitance, from which are calculated an ac conductivity attributed provisionally to ions and an activation energy for that conductivity. Electronic conductivity is directly measured. The screening procedure applied to sodium beta-alumina yielded acceptable values for conductivity and activation energy.

High temperature conductivity of potassium-beta(double prime)-alumina

NASA Technical Reports Server (NTRS)

Williams, R. M.; Jeffries-Nakamura, B.; Underwood, M. L.; Ryan, M. A.; O'Connor, D.; Kikkert, S.

1992-01-01

Potassium beta(double prime)-alumina (BDPA) single crystals have been reported by several groups to leave higher ionic conductivity than sodium BDPA crystals at room temperature, and similar conductivities are obtained at temperatures up to 600-700 K. Potassium BDPA ceramics have been reported to have significantly poorer conductivities than those of sodium BDPA ceramics, but conductivity measurements at temperatures above 625 K have not been reported. In this study, K(+)-BDPA ceramics were prepared from Na(+)-BDPA ceramic using a modified version of the exchange reaction with KCl vapor reported by Crosbie and Tennenhouse (1982), and the conductivity has been measured in K vapor at temperatures up to 1223 K, using the method of Cole et al. (1979). The results indicate reasonable agreement with earlier data on K(+)-BDPA ceramic measured in a liquid K cell, but show that the K(+)-BDPA ceramic's conductivity approaches that of Na(+)-BDPA ceramic at higher temperatures, being within a factor of four at 700 K and 60 percent of the conductivity of Na(+)-BDPA at T over 1000 K. Both four-probe dc conductivity and four probe ac impedance measurements were used to characterize the conductivity. A rather abrupt change in the grain boundary resistance suggesting a possible phase change in the intergranular material, potassium aluminate, is seen in the ac impedance behavior.

Mutual cancellation between tones presented by air conduction, by bone conduction and by non-osseous (soft tissue) bone conduction.

PubMed

Chordekar, Shai; Kriksunov, Leonid; Kishon-Rabin, Liat; Adelman, Cahtia; Sohmer, Haim

2012-01-01

Auditory sensation can be elicited not only by air conducted (AC) sound or bone conducted (BC) sound, but also by stimulation of soft tissue (STC) sites on the head and neck relatively distant from deeply underlying bone. Tone stimulation by paired combinations of AC with BC (mastoid) and/or with soft tissue conduction produce the same pitch sensation, mutual masking and beats. The present study was designed to determine whether they can also cancel each other. The study was conducted on ten normal hearing subjects. Tones at 2 kHz were presented in paired combinations by AC (insert earphone), by BC (bone vibrator) at the mastoid, and by the same bone vibrator to several STC sites; e.g. the neck, the sterno-cleido-mastoid muscle, the eye, and under the chin, shifting the phases between the pairs. Subjects reported changes in loudness and cancellation. The phase for cancellation differed across subjects. Neck muscle manipulations (changes in head position) led to alterations in the phase at which cancellation was reported. Cancellation was also achieved between pairs of tones to two STC sites. The differing phases for cancellation across subjects and the change in phase accompanying different head positions may be due to the different acoustic impedances of the several tissues in the head and neck. A major component of auditory stimulation by STC may not induce actual skull bone vibrations and may not involve bulk fluid volume displacements. Copyright © 2011 Elsevier B.V. All rights reserved.

Anatomy of the chiral magnetic effect in and out of equilibrium

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kharzeev, Dmitri; Stephanov, Mikhail; Yee, Ho-Ung

Here, we identify a new contribution to the chiral magnetic conductivity at finite frequencies—the magnetization current. This allows us to quantitatively reproduce the known field-theoretic time-dependent (AC) chiral magnetic response in terms of kinetic theory. We also evaluate the corresponding AC chiral magnetic conductivity in two-flavor QCD plasma at weak coupling. The magnetization current results from the spin response of chiral quasiparticles to magnetic field, and is thus proportional to the quasiparticle’s g -factor. Furthemrore, in condensed matter systems, where the chiral quasiparticles are emergent and the g -factor can significantly differ from 2, this opens up the possibility ofmore » tuning the AC chiral magnetic response.« less

Anatomy of the chiral magnetic effect in and out of equilibrium

DOE PAGES

Kharzeev, Dmitri; Stephanov, Mikhail; Yee, Ho-Ung

2017-03-28

Here, we identify a new contribution to the chiral magnetic conductivity at finite frequencies—the magnetization current. This allows us to quantitatively reproduce the known field-theoretic time-dependent (AC) chiral magnetic response in terms of kinetic theory. We also evaluate the corresponding AC chiral magnetic conductivity in two-flavor QCD plasma at weak coupling. The magnetization current results from the spin response of chiral quasiparticles to magnetic field, and is thus proportional to the quasiparticle’s g -factor. Furthemrore, in condensed matter systems, where the chiral quasiparticles are emergent and the g -factor can significantly differ from 2, this opens up the possibility ofmore » tuning the AC chiral magnetic response.« less

Simultaneous measurement of skin potential and conductance in electrodermal response monitoring

NASA Astrophysics Data System (ADS)

Jabbari, A.; Johnsen, B.; Grimnes, S.; Martinsen, Ø. G.

2010-04-01

Measurement of electrodermal activity (EDA) has been an important tool in psychophysiological research. The emotional sweat activity is very sensitive to psychological stimuli or conditions. The changes are easily detected by means of electrical measurements and since the sweat ducts are predominantly resistive, a low-frequency conductance measurement is appropriate for measurement of skin conductance in electrodermal response. The main purpose of this study was to develop a measuring system where DC current was replaced by a small AC current in a system so the DC potential and AC conductance could be measured simultaneously at the same skin site. A small, battery operated, PDA based instrument has been developed. The preliminary results of this ongoing study show that there is additional information in the DC potential channel and that different stimuli seem to produce slightly different response patterns.

Microstructural and electrical properties of PVA/PVP polymer blend films doped with cupric sulphate

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hemalatha, K.; Gowtham, G. K.; Somashekarappa, H., E-mail: drhssappa@gmail.com

2016-05-23

A series of polyvinyl alcohol (PVA)/polyvinyl pyrrolidone (PVP) polymer blends added with different concentrations of cupric sulphate (CuSO{sub 4}) were prepared by solution casting method and were subjected to X-ray diffraction (XRD) and Ac conductance measurements. An attempt has been made to study the changes in crystal imperfection parameters in PVA/PVP blend films with the increase in concentration of CuSO{sub 4}. Results show that decrease in micro crystalline parameter values is accompanied with increase in the amorphous content in the film which is the reason for film to have more flexibility, biodegradability and good ionic conductivity. AC conductance measurements inmore » these films show that the conductivity increases as the concentration of CuSO{sub 4} increases. These films were suitable for electro chemical applications.« less

Superconductivity in the graphene monolayer calculated using the Kubo formulalism

NASA Astrophysics Data System (ADS)

Lima, L. S.

2018-03-01

We have employed the massless Dirac's fermions formalism together with the Kubo's linear response theory to study the transport by electrons in the graphene monolayer. We have calculated the electric conductivity and verified the behavior of the AC and DC electric conductivities of the system that is known to be a relativistic electron plasma. Our results show a superconductor behavior to the electron transport and consequently the spin transport for all values of T > 0 and a behavior of the AC conductivity tending to infinity in the limit ω → 0. In T = 0 our results show an insulator behavior with a transition from a superconductor state at T > 0 to an insulator state at T = 0 .

Experimental Analysis of the Mechanism of Hearing under Water

PubMed Central

Chordekar, Shai; Kishon-Rabin, Liat; Kriksunov, Leonid; Adelman, Cahtia; Sohmer, Haim

2015-01-01

The mechanism of human hearing under water is debated. Some suggest it is by air conduction (AC), others by bone conduction (BC), and others by a combination of AC and BC. A clinical bone vibrator applied to soft tissue sites on the head, neck, and thorax also elicits hearing by a mechanism called soft tissue conduction (STC) or nonosseous BC. The present study was designed to test whether underwater hearing at low intensities is by AC or by osseous BC based on bone vibrations or by nonosseous BC (STC). Thresholds of normal hearing participants to bone vibrator stimulation with their forehead in air were recorded and again when forehead and bone vibrator were under water. A vibrometer detected vibrations of a dry human skull in all similar conditions (in air and under water) but not when water was the intermediary between the sound source and the skull forehead. Therefore, the intensities required to induce vibrations of the dry skull in water were significantly higher than the underwater hearing thresholds of the participants, under conditions when hearing by AC and osseous BC is not likely. The results support the hypothesis that hearing under water at low sound intensities may be attributed to nonosseous BC (STC). PMID:26770975

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.

Evaluation of shuttle solid rocket booster case materials. Corrosion and stress corrosion susceptibility of several high temperature materials

NASA Technical Reports Server (NTRS)

Pionke, L. J.; Garland, K. C.

1973-01-01

Candidate alloys for the Shuttle Solid Rocket Booster (SRB) case were tested under simulated service conditions to define subcritical flaw growth behavior under both sustained and cyclic loading conditions. The materials evaluated were D6AC and 18 Ni maraging steel, both heat treated to a nominal yield strength of 1380 MN/sq m (200 ksi). The sustained load tests were conducted by exposing precracked, stressed specimens of both alloys to alternate immersion in synthetic sea water. It was found that the corrosion and stress corrosion resistance of the 18 Ni maraging steel were superior to that of the D6AC steel under these test conditions. It was also found that austenitizing temperature had little influence on the threshold stress intensity of the D6AC. The cyclic tests were conducted by subjecting precracked surface-flawed specimens of both alloys to repeated load/thermal/environmental profiles which were selected to simulate the SRB missions. It was found that linear removal operations that involve heating to 589 K (600 F) cause a decrease in cyclic life of D6AC steel relative to those tests conducted with no thermal cycling.

Dielectric Properties of PANI/CuO Nanocomposites

NASA Astrophysics Data System (ADS)

Ambalagi, Sharanabasamma M.; Devendrappa, Mahalesh; Nagaraja, Sannakki; Sannakki, Basavaraja

2018-02-01

The combustion method is used to prepare the Copper Oxide (CuO) nanoparticles. The nanocomposites of Polyaniline (PANI) by doping with copper oxide nanoparticles have synthesized at 10, 20, 30, 40 and 50 different weight percentages during the in-situ polymerization. The samples of nanocomposite of PANI-CuO were characterized by using X-Ray diffraction (XRD) technique. The physical properties such as dielectric constant, dielectric loss and A C conductivity of the nanocomposites are studied as a function of frequency in the range 5Hz-35MHz at room temperature. It is found that the dielectric constant decreases as the frequency increases. The dielectric constant it remains constant at higher frequencies and it is also observed that in particular frequency both the dielectric constant and dielectric loss are decreased as a weight percentage of CuO increased. In case of AC conductivity it is found that as the frequency increases the AC conductivity remains constant up to 3.56MHz and afterwards it increases as frequency increases. This is due to the increase in charge carriers through the hopping mechanism in the polymer nanocomposites. It is also observed that as a weight percentage of CuO increased the AC conductivity is also increasing at a particular frequency.

Alternating current characterization of nano-Pt(II) octaethylporphyrin (PtOEP) thin film as a new organic semiconductor

NASA Astrophysics Data System (ADS)

M, Dongol; M, M. El-Nahass; A, El-Denglawey; A, A. Abuelwafa; T, Soga

2016-06-01

Alternating current (AC) conductivity and dielectric properties of thermally evaporated Au/PtOEP/Au thin films are investigated each as a function of temperature (303 K-473 K) and frequency (50 Hz-5 MHz). The frequency dependence of AC conductivity follows the Jonscher universal dynamic law. The AC-activation energies are determined at different frequencies. It is found that the correlated barrier hopping (CBH) model is the dominant conduction mechanism. The variation of the frequency exponent s with temperature is analyzed in terms of the CBH model. Coulombic barrier height W m , hopping distance R ω , and the density of localized states N(E F) are valued at different frequencies. Dielectric constant ɛ 1(ω,T) and dielectric loss ɛ 2(ω,T) are discussed in terms of the dielectric polarization process. The dielectric modulus shows the non-Debye relaxation in the material. The extracted relaxation time by using the imaginary part of modulus (M″) is found to follow the Arrhenius law.

Improvement of thermal radiation characteristic of AC servomotor using Al-CNT composite material

NASA Astrophysics Data System (ADS)

Kikuchi, Y.; Wakiwaka, H.; Yanagihara, M.

2018-02-01

This study deals with a high thermal conductivity material of aluminum-carbon nanotube (CNT) composite with carbon fiber (CF) and the high radiation performance of AC servomotor using a stator made of nanotube composite material. The composite fabrication process was performed by melting a mixture of granular aluminum of less than 200 μm and CNT under conditions of pressed atmosphere at the same time. Two kinds of motors made using aluminum and the composite were evaluated to confirm the effect of thermal conductivity as the motor stator. A test rod of the composite with 14 wt% CF-7 wt% CNT-aluminum indicated the excellent thermal conductivity of 169 W/(mK) in the radial direction and 173 W/(mK) in the lengthwise direction. According to the obtained temperature radiation characteristic of the AC servomotor, the composite stator using CNT decreased the consumption energy to 16% compared to the conventional one. As a result, the highly efficient motor improved the radiation characteristic using the CNT composite stator.

Temperature Effects of Dielectric Properties of ER Fluids

NASA Astrophysics Data System (ADS)

Qiu, Z. Y.; Hu, L.; Liu, M. W.; Bao, H. X.; Jiang, Y. G.; Zhou, L. W.; Tang, Y.; Gao, Z.; Sun, M.; Korobko, E. V.

Under the consideration of the role that energy transfer and dissipation play in ER effect, an improved theory frame for ER effects, polarization-dissipation-structure-rheology, is suggested. The theory frame is substantiated by the basic physical laws and certain critical experimental facts. The dielectric response of a diatomite ER fluid to temperature is measured in the temperature range of 140 K to 400 K. By comparison of the DC conductivity with the AC effective conductivity of the sample, we found that the AC dielectric loss consists of two parts. One part comes from the DC conductivity, the other from the response of the bound charges in scope of particle to AC field. It is suggested that the response of bound charges is very important to ER effects. Besides, the effect of temperature on shear stress is measured, and interpreted based on the dielectric measurements. The source of two loss peaks in the curve of the dielectric loss versus temperature is not clear.

AC conduction of Ba1-xCaxTiO3 and BZT-BCTx

NASA Astrophysics Data System (ADS)

Khien, Nguyen Van; Huy, Than Trong; Hong, Le Van

2018-03-01

Ba1-xCaxTiO3 (BCTx), (x =0.0-0.3) and Ba0.8Zr0.2TiO3-Ba1-xCaxTiO3 (BZT-BCTx), (x=0.15-0.35) were fabricated by the solid state reaction method. Phase structure of the material samples was identified by X-ray diffraction. The impedance versus frequency in a range of 100 Hz to 2.5 MHz was measured for all the samples at room temperature. AC conductivity versus frequency of the BCTx and BZT-BCTx was evaluated and fitted by using the extended Universal Dielectric Response (UDR) equations. The fitting results were discussed in detail and shown that the localized reorientation polarization-based mechanism is most contributed in BCTx matrial samples. Basically both two the hopping polaron and polarization mechanisms play roles in BZT-BCTx material samples. In contrary the short-range polaron hopping is dominated in ac conductivity of BZT-BCTx material samples in low frequency range.

Impedance spectroscopic analysis of composite electrode from activated carbon/conductive materials/ruthenium oxide for supercapacitor applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Taer, E.; Awitdrus,; Farma, R.

Activated carbon powders (ACP) were produced from the KOH treated pre-carbonized rubber wood sawdust. Different conductive materials (graphite, carbon black and carbon nanotubes (CNTs)) were added with a binder (polivinylidene fluoride (PVDF)) into ACP to improve the supercapacitive performance of the activated carbon (AC) electrodes. Symmetric supercapacitor cells, fabricated using these AC electrodes and 1 molar H{sub 2}SO{sub 4} electrolyte, were analyzed using a standard electrochemical impedance spectroscopy technique. The addition of graphite, carbon black and CNTs was found effective in reducing the cell resistance from 165 to 68, 23 and 49 Ohm respectively, and increasing the specific capacitance ofmore » the AC electrodes from 3 to 7, 17, 32 F g{sup −1} respectively. Since the addition of CNTs can produce the highest specific capacitance, CNTs were chosen as a conductive material to produce AC composite electrodes that were added with 2.5 %, 5 % and 10 % (by weight) electro-active material namely ruthenium oxide; PVDF binder and CNTs contents were kept at 5 % by weight in each AC composite produced. The highest specific capacitance of the cells obtained in this study was 86 F g{sup −1}, i.e. for the cell with the resistance of 15 Ohm and composite electrode consists of 5 % ruthenium oxide.« less

Impedance Spectroscopy and AC Conductivity Studies of Bulk 3-Amino-7-(dimethylamino)-2-methyl-hydrochloride

NASA Astrophysics Data System (ADS)

El-Shabaan, M. M.

2018-02-01

Impedance spectroscopy and alternating-current (AC) conductivity (σ AC) studies of bulk 3-amino-7-(dimethylamino)-2-methyl-hydrochloride (neutral red, NR) have been carried out over the temperature (T) range from 303 K to 383 K and frequency (f) range from 0.5 kHz to 5 MHz. Dielectric data were analyzed using the complex impedance (Z *) and complex electric modulus (M *) for bulk NR at various temperatures. The impedance loss peaks were found to shift towards high frequencies, indicating an increase in the relaxation time (τ 0) and loss in the material, with increasing temperature. For each temperature, a single depressed semicircle was observed at high frequencies, originating from the bulk transport, and a spike in the low-frequency region, resulting from the electrode effect. Fitting of these curves yielded an equivalent circuit containing a parallel combination of a resistance R and constant-phase element (CPE) Q. The carrier transport in bulk NR is governed by the correlated barrier hopping (CBH) mechanism, some parameters of which, such as the maximum barrier height (W M), charge density (N), and hopping distance (r), were determined as functions of both temperature and frequency. The frequency dependence of σ AC at different temperatures indicated that the conduction in bulk NR is a thermally activated process. The σ AC value at different frequencies increased linearly with temperature.

Effects of pipette modulation and imaging distances on ion currents measured with scanning ion conductance microscopy (SICM).

PubMed

Chen, Chiao-Chen; Baker, Lane A

2011-01-07

Local conductance variations can be estimated by measuring ion current magnitudes with scanning ion conductance microscopy (SICM). Factors which influence image quality and quantitation of ion currents measured with SICM have been evaluated. Specifically, effects of probe-sample separation and pipette modulation have been systematically studied for the case of imaging conductance variations at pores in a polymer membrane under transmembrane concentration gradients. The influence of probe-sample separation on ion current images was evaluated using distance-modulated (ac) feedback. Approach curves obtained using non-modulated (dc) feedback were also recorded to determine the relative influence of pipette-generated convection by comparison of ion currents measured with both ac and dc feedback modes. To better interpret results obtained, comparison to a model based on a disk-shaped geometry for nanopores in the membrane, as well as relevant position-dependent parameters of the experiment is described. These results advance our current understanding of conductance measurements with SICM.

Effect of Microwave Non thermal Plasma Irradiation on the Adsorptive Properties of Active Carbon Preliminarily Impregnated with Poly(vinyl alcohol)

NASA Astrophysics Data System (ADS)

Ueshima, Masato; Toda, Eriko; Nakajima, Yuki; Sugiyama, Kazuo

2010-08-01

Microwave non thermal plasma irradiation was conducted on active carbon (AC) preliminarily impregnated with poly(vinyl alcohol) (PVA) in order to modify the adsorption properties of active carbon, particularly to increase hydrophobicity. The plasma was produced by applying microwave power on the PVA-impregnated active carbon (PVA/AC) placed in a low vacuum chamber (<10 Torr). The surface of the plasma-treated PVA/AC was imaged using scanning electron microscopy and atomic force microscopy (SEM and AFM, respectively), and analyzed using X-ray photoelectron spectroscopy (XPS). Hydrophobicity of the plasma-treated PVA/AC was compared to that of untreated PVA/AC and AC by a sinking test in water/methanol mixed solutions. The hydrophobicity drastically increased for PVA/AC treatment with 1-min plasma irradiation. The AFM results indicated that the surface roughness of the PVA/AC was dependent upon the hydrophobicity, rather than reduction of free energy due to reduction of polarized functional groups. NaOH and HCl adsorption onto the plasma-treated PVA/AC was also measured. Adsorption capacity of plasma-treated PVA/AC increased for NaOH, whereas it decreased for HCl. The plasma treatment not only increased the hydrophobicity of PVA/AC, but also changed its acid-base adsorption properties. We have developed a new material based on active carbon, which is light, hydrophobic and electrically conductive by using a combination of PVA sintering and plasma irradiation.

The Effects of Theta and Gamma tACS on Working Memory and Electrophysiology

PubMed Central

Pahor, Anja; Jaušovec, Norbert

2018-01-01

A single blind sham-controlled study was conducted to explore the effects of theta and gamma transcranial alternating current stimulation (tACS) on offline performance on working memory tasks. In order to systematically investigate how specific parameters of tACS affect working memory, we manipulated the frequency of stimulation (theta frequency vs. gamma frequency), the type of task (n-back vs. change detection task) and the content of the tasks (verbal vs. figural stimuli). A repeated measures design was used that consisted of three sessions: theta tACS, gamma tACS and sham tACS. In total, four experiments were conducted which differed only with respect to placement of tACS electrodes (bilateral frontal, bilateral parietal, left fronto-parietal and right-fronto parietal). Healthy female students (N = 72) were randomly assigned to one of these groups, hence we were able to assess the efficacy of theta and gamma tACS applied over different brain areas, contrasted against sham stimulation. The pre-post/sham resting electroencephalogram (EEG) analysis showed that theta tACS significantly affected theta amplitude, whereas gamma tACS had no significant effect on EEG amplitude in any of the frequency bands of interest. Gamma tACS did not significantly affect working memory performance compared to sham, and theta tACS led to inconsistent changes in performance on the n-back tasks. Active theta tACS significantly affected P3 amplitude and latency during performance on the n-back tasks in the bilateral parietal and right-fronto parietal protocols. PMID:29375347

Continuous-flow trapping and localized enrichment of micro- and nano-particles using induced-charge electrokinetics.

PubMed

Zhao, Cunlu; Yang, Chun

2018-02-14

In this work, we report an effective microfluidic technique for continuous-flow trapping and localized enrichment of micro- and nano-particles by using induced-charge electrokinetic (ICEK) phenomena. The proposed technique utilizes a simple microfluidic device that consists of a straight microchannel and a conducting strip attached to the bottom wall of the microchannel. Upon application of the electric field along the microchannel, the conducting strip becomes polarized to introduce two types of ICEK phenomena, the ICEK flow vortex and particle dielectrophoresis, and they are identified by a theoretical model formulated in this study to be jointly responsible for the trapping of particles over the edge of the conducting strip. Our experiments showed that successful trapping requires an AC/DC combined electric field: the DC component is mainly to induce electroosmotic flow for transporting particles to the trapping location; the AC component induces ICEK phenomena over the edge of the conducting strip for particle trapping. The performance of the technique is examined with respect to the applied electric voltage, AC frequency and the particle size. We observed that the trapped particles form a narrow band (nearly a straight line) defined by the edge of the conducting strip, thereby allowing localized particle enrichment. For instance, we found that under certain conditions a high particle enrichment ratio of 200 was achieved within 30 seconds. We also demonstrated that the proposed technique was able to trap particles from several microns down to several tens of nanometer. We believe that the proposed ICEK trapping would have great flexibility that the trapping location can be readily varied by controlling the location of the patterned conducting strip and multiple-location trapping can be expected with the use of multiple conducting strips.

Dielectric and ac ionic conductivity investigation of Li2SrP2O7

NASA Astrophysics Data System (ADS)

Ajili, O.; Louati, B.; Guidara, K.

2018-07-01

The pyrophosphate Li2SrP2O7 compound has been synthesized by the classic ceramic method and characterized by X-ray diffraction, IR, Raman and electrical impedance spectroscopy. Detailed electrical properties of the compound were analyzed as a function of frequency (209 Hz-1 MHz) and temperature (519-628) K. Impedance analysis exhibits the grain and grain boundary contribution to the electrical response of the sample. The temperature dependence of these contribution obey the Arrhenius law with activation energies (1.03 ± 0.05) and (1.25 ± 0.05) eV, respectively. The ac conductivity for grain contribution was interpreted using the universal Jonscher's power law. The temperature dependence of frequency exponent s was investigated to understand the conduction mechanism. The correlated barrier hopping model was found to be the best model describing the conduction mechanism.

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.

Dielectric and ac ionic conductivity investigation of Li2SrP2O7

NASA Astrophysics Data System (ADS)

Ajili, O.; Louati, B.; Guidara, K.

2018-02-01

The pyrophosphate Li2SrP2O7 compound has been synthesized by the classic ceramic method and characterized by X-ray diffraction, IR, Raman and electrical impedance spectroscopy. Detailed electrical properties of the compound were analyzed as a function of frequency (209 Hz-1 MHz) and temperature (519-628) K. Impedance analysis exhibits the grain and grain boundary contribution to the electrical response of the sample. The temperature dependence of these contribution obey the Arrhenius law with activation energies (1.03 ± 0.05) and (1.25 ± 0.05) eV, respectively. The ac conductivity for grain contribution was interpreted using the universal Jonscher's power law. The temperature dependence of frequency exponent s was investigated to understand the conduction mechanism. The correlated barrier hopping model was found to be the best model describing the conduction mechanism.

Enhanced ionic conductivity of AgI nanowires/AAO composites fabricated by a simple approach.

PubMed

Liu, Li-Feng; Lee, Seung-Woo; Li, Jing-Bo; Alexe, Marin; Rao, Guang-Hui; Zhou, Wei-Ya; Lee, Jae-Jong; Lee, Woo; Gösele, Ulrich

2008-12-10

AgI nanowires/anodic aluminum oxide (AgI NWs/AAO) composites have been fabricated by a simple approach, which involves the thermal melting of AgI powders on the surface of the AAO membrane, followed by the infiltration of the molten AgI inside the nanochannels. As-prepared AgI nanowires have corrugated outer surfaces and are polycrystalline according to scanning electron microscopy (SEM) and transmission electron microscopy (TEM) observations. X-ray diffraction (XRD) shows that a considerable amount of 7H polytype AgI exists in the composites, which is supposed to arise from the interfacial interactions between the embedded AgI and the alumina. AC conductivity measurements for the AgI nanowires/AAO composites exhibit a notable conductivity enhancement by three orders of magnitude at room temperature compared with that of pristine bulk AgI. Furthermore, a large conductivity hysteresis and abnormal conductivity transitions were observed in the temperature-dependent conductivity measurements, from which an ionic conductivity as high as 8.0 × 10(2) Ω(-1) cm(-1) was obtained at around 70 °C upon cooling. The differential scanning calorimetry (DSC) result demonstrates a similar phase transition behavior as that found in the AC conductivity measurements. The enhanced ionic conductivity, as well as the abnormal phase transitions, can be explained in terms of the existence of the highly conducting 7H polytype AgI and the formation of well-defined conduction paths in the composites.

Judgement of Breath Alcohol Concentration Levels Among Pedestrians in the Night-Time Economy-A Street-Intercept Field Study.

PubMed

Cameron, M P; Roskruge, M J; Droste, N; Miller, P G

2018-05-01

To evaluate how well people in the night-time economy can assess their own breath alcohol concentration (BrAC), in the context of a change in breath alcohol limits for driving. We conducted a field study of 242 participants over 5 nights in the central business district of a university town in New Zealand. Participants completed a short survey, which included questions on their self-reported level of intoxication and the self-estimated BrAC. At the conclusion of the interview each participant was breath-tested. We compared actual and self-estimated BrAC using a scatter plot and multiple regression methods. The average BrAC error was 61.7 μg/l, meaning that on average participants overestimate their BrAC. Participants with a BrAC below 487 μg/l tended to overestimate their BrAC on average, and those with a BrAC above 487 μg/l tended to underestimate their BrAC on average. Regression results supported this observation, but also found that men who are not 'out on a typical night' overestimate their BrAC by more. Drinkers in this naturalistic setting have little idea of their level of intoxication, as measured by BrAC. However, this uncertainty may be advantageous to public health outcomes, since if drinkers are uncertain about their level of intoxication relative to the legal limit, this may lead them to avoid drunk driving. A field study of drinkers in the night-time economy of a New Zealand university town was conducted to evaluate how well drinkers can assess their breath alcohol concentration (BrAC). Drinkers in this setting inaccurately estimate their intoxication, and those with higher BrAC tended to underestimate their BrAC on average.

Cartilage conduction is characterized by vibrations of the cartilaginous portion of the ear canal.

PubMed

Nishimura, Tadashi; Hosoi, Hiroshi; Saito, Osamu; Miyamae, Ryosuke; Shimokura, Ryota; Yamanaka, Toshiaki; Kitahara, Tadashi; Levitt, Harry

2015-01-01

Cartilage conduction (CC) is a new form of sound transmission which is induced by a transducer being placed on the aural cartilage. Although the conventional forms of sound transmission to the cochlea are classified into air or bone conduction (AC or BC), previous study demonstrates that CC is not classified into AC or BC (Laryngoscope 124: 1214-1219). Next interesting issue is whether CC is a hybrid of AC and BC. Seven volunteers with normal hearing participated in this experiment. The threshold-shifts by water injection in the ear canal were measured. AC, BC, and CC thresholds at 0.5-4 kHz were measured in the 0%-, 40%-, and 80%-water injection conditions. In addition, CC thresholds were also measured for the 20%-, 60%-, 100%-, and overflowing-water injection conditions. The contributions of the vibrations of the cartilaginous portion were evaluated by the threshold-shifts. For AC and BC, the threshold-shifts by the water injection were 22.6-53.3 dB and within 14.9 dB at the frequency of 0.5-4 kHz, respectively. For CC, when the water was filled within the bony portion, the thresholds were elevated to the same degree as AC. When the water was additionally injected to reach the cartilaginous portion, the thresholds at 0.5 and 1 kHz dramatically decreased by 27.4 and 27.5 dB, respectively. In addition, despite blocking AC by the injected water, the CC thresholds in force level were remarkably lower than those for BC. The vibration of the cartilaginous portion contributes to the sound transmission, particularly in the low frequency range. Although the airborne sound is radiated into the ear canal in both BC and CC, the mechanism underlying its generation is different between them. CC generates airborne sound in the canal more efficiently than BC. The current findings suggest that CC is not a hybrid of AC and BC.

Cartilage Conduction Is Characterized by Vibrations of the Cartilaginous Portion of the Ear Canal

PubMed Central

Nishimura, Tadashi; Hosoi, Hiroshi; Saito, Osamu; Miyamae, Ryosuke; Shimokura, Ryota; Yamanaka, Toshiaki; Kitahara, Tadashi; Levitt, Harry

2015-01-01

Cartilage conduction (CC) is a new form of sound transmission which is induced by a transducer being placed on the aural cartilage. Although the conventional forms of sound transmission to the cochlea are classified into air or bone conduction (AC or BC), previous study demonstrates that CC is not classified into AC or BC (Laryngoscope 124: 1214–1219). Next interesting issue is whether CC is a hybrid of AC and BC. Seven volunteers with normal hearing participated in this experiment. The threshold-shifts by water injection in the ear canal were measured. AC, BC, and CC thresholds at 0.5–4 kHz were measured in the 0%-, 40%-, and 80%-water injection conditions. In addition, CC thresholds were also measured for the 20%-, 60%-, 100%-, and overflowing-water injection conditions. The contributions of the vibrations of the cartilaginous portion were evaluated by the threshold-shifts. For AC and BC, the threshold-shifts by the water injection were 22.6–53.3 dB and within 14.9 dB at the frequency of 0.5–4 kHz, respectively. For CC, when the water was filled within the bony portion, the thresholds were elevated to the same degree as AC. When the water was additionally injected to reach the cartilaginous portion, the thresholds at 0.5 and 1 kHz dramatically decreased by 27.4 and 27.5 dB, respectively. In addition, despite blocking AC by the injected water, the CC thresholds in force level were remarkably lower than those for BC. The vibration of the cartilaginous portion contributes to the sound transmission, particularly in the low frequency range. Although the airborne sound is radiated into the ear canal in both BC and CC, the mechanism underlying its generation is different between them. CC generates airborne sound in the canal more efficiently than BC. The current findings suggest that CC is not a hybrid of AC and BC. PMID:25768088

Affirmative Consent: What Do College Student Leaders Think about "Yes Means Yes" as the Standard for Sexual Behavior?

ERIC Educational Resources Information Center

Curtis, Jena Nicols; Burnett, Susan

2017-01-01

Affirmative consent (AC) is becoming the standard for sexual behavior between students. However, little is known about how college students interpret and practice AC. We conducted in-depth, semistructured interviews with a purposeful sample of 31 undergraduate students to understand students' perceptions of AC and how it was practiced in their…

Effect of proton-conduction in electrolyte on electric efficiency of multi-stage solid oxide fuel cells

PubMed Central

Matsuzaki, Yoshio; Tachikawa, Yuya; Somekawa, Takaaki; Hatae, Toru; Matsumoto, Hiroshige; Taniguchi, Shunsuke; Sasaki, Kazunari

2015-01-01

Solid oxide fuel cells (SOFCs) are promising electrochemical devices that enable the highest fuel-to-electricity conversion efficiencies under high operating temperatures. The concept of multi-stage electrochemical oxidation using SOFCs has been proposed and studied over the past several decades for further improving the electrical efficiency. However, the improvement is limited by fuel dilution downstream of the fuel flow. Therefore, evolved technologies are required to achieve considerably higher electrical efficiencies. Here we present an innovative concept for a critically-high fuel-to-electricity conversion efficiency of up to 85% based on the lower heating value (LHV), in which a high-temperature multi-stage electrochemical oxidation is combined with a proton-conducting solid electrolyte. Switching a solid electrolyte material from a conventional oxide-ion conducting material to a proton-conducting material under the high-temperature multi-stage electrochemical oxidation mechanism has proven to be highly advantageous for the electrical efficiency. The DC efficiency of 85% (LHV) corresponds to a net AC efficiency of approximately 76% (LHV), where the net AC efficiency refers to the transmission-end AC efficiency. This evolved concept will yield a considerably higher efficiency with a much smaller generation capacity than the state-of-the-art several tens-of-MW-class most advanced combined cycle (MACC). PMID:26218470

Dielectric and impedance study of praseodymium substituted Mg-based spinel ferrites

NASA Astrophysics Data System (ADS)

Farid, Hafiz Muhammad Tahir; Ahmad, Ishtiaq; Ali, Irshad; Ramay, Shahid M.; Mahmood, Asif; Murtaza, G.

2017-07-01

Spinel ferrites with nominal composition MgPryFe2-yO4 (y = 0.00, 0.025, 0.05, 0.075, 0.10) were prepared by sol-gel method. Temperature dependent DC electrical conductivity and drift mobility were found in good agreement with each other, reflecting semiconducting behavior. The dielectric properties of all the samples as a function of frequency (1 MHz-3 GHz) were measured at room temperature. The dielectric constant and complex dielectric constant of these samples decreased with the increase of praseodymium concentration. In the present spinel ferrite, Cole-Cole plots were used to separate the grain and grain boundary's effects. The substitution of praseodymium ions in Mg-based spinel ferrites leads to a remarkable rise of grain boundary's resistance as compared to the grain's resistance. As both AC conductivity and Cole-Cole plots are the functions of concentration, they reveal the dominant contribution of grain boundaries in the conduction mechanism. AC activation energy was lower than dc activation energy. Temperature dependence normalized AC susceptibility of spinel ferrites reveals that MgFe2O4 exhibits multi domain (MD) structure with high Curie temperature while on substitution of praseodymium, MD to SD transitions occurs. The low values of conductivity and low dielectric loss make these materials best candidate for high frequency application.

Effect of proton-conduction in electrolyte on electric efficiency of multi-stage solid oxide fuel cells.

PubMed

Matsuzaki, Yoshio; Tachikawa, Yuya; Somekawa, Takaaki; Hatae, Toru; Matsumoto, Hiroshige; Taniguchi, Shunsuke; Sasaki, Kazunari

2015-07-28

Solid oxide fuel cells (SOFCs) are promising electrochemical devices that enable the highest fuel-to-electricity conversion efficiencies under high operating temperatures. The concept of multi-stage electrochemical oxidation using SOFCs has been proposed and studied over the past several decades for further improving the electrical efficiency. However, the improvement is limited by fuel dilution downstream of the fuel flow. Therefore, evolved technologies are required to achieve considerably higher electrical efficiencies. Here we present an innovative concept for a critically-high fuel-to-electricity conversion efficiency of up to 85% based on the lower heating value (LHV), in which a high-temperature multi-stage electrochemical oxidation is combined with a proton-conducting solid electrolyte. Switching a solid electrolyte material from a conventional oxide-ion conducting material to a proton-conducting material under the high-temperature multi-stage electrochemical oxidation mechanism has proven to be highly advantageous for the electrical efficiency. The DC efficiency of 85% (LHV) corresponds to a net AC efficiency of approximately 76% (LHV), where the net AC efficiency refers to the transmission-end AC efficiency. This evolved concept will yield a considerably higher efficiency with a much smaller generation capacity than the state-of-the-art several tens-of-MW-class most advanced combined cycle (MACC).

[Accidents of the everyday life (AcVC) in children in Dakar: about 201 cases].

PubMed

Mohamed, Azhar Salim; Sagna, Aloïse; Fall, Mbaye; Ndoye, Ndeye Aby; Mbaye, Papa Alassane; Fall, Aimé Lakh; Diaby, Alou; Ndour, Oumar; Ngom, Gabriel

2017-01-01

Accidents of everyday life (AcVC) are common in children and can led to disabling injuries and death. This study aimed to analyze the epidemiological aspects of AcVC and the related injury mechanisms in Dakar. We conducted a descriptive, cross-sectional study conducted from 1 January 2013 to 30 June 2013. All the children victims of domestic accidents, sport and leisure accidents or school accidents were included. We studied some general parameters and some parameters related to each type of AcVC. Two hundred and one children were included, accounting for 27% of emergency consultations. There were 148 boys and 53 girls. Children less than 5 years of age were most affected (37.8%). Football and wrestling game were the main causes of AcVC. AcVC occur mainly at home (58.2%) and in the areas of sport and recreation (31.8%). The fractures predominated in the different types of AcVC: 54.9% of domestic accidents, 68.8% of sport and recreation accidents and 40% of school accidents. From an epidemiological perspective, our results are superimposable to literature. Fractures predominated contrary to literature where bruises were preponderant. Wrestling game is the main cause of these fractures, after football. The acquisition of knowledge about the epidemiological aspects of AcVC and the related injury mechanisms will allow for prevention campaigns in Dakar.

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.

Imaginary part of Hall conductivity in a tilted doped Weyl semimetal with both broken time-reversal and inversion symmetry

NASA Astrophysics Data System (ADS)

Mukherjee, S. P.; Carbotte, J. P.

2018-01-01

We consider a Weyl semimetal with finite doping and tilt within a continuum model Hamiltonian with both broken time-reversal and inversion symmetry. We calculate the absorptive part of the anomalous ac Hall conductivity as a function of photon energy Ω for both type-I and type-II Weyl semimetals. For a given Weyl node, changing the sign of its chirality or of its tilt changes the sign of its contribution to the absorptive Hall conductivity with no change in magnitude. For a noncentrosymmetric system we find that there are ranges of photon energies for which only the positive or only the negative-chirality node contributes to the imaginary (absorptive) part of the Hall conductivity. There are also other photon energies where both chiralities contribute, and there can be other ranges of Ω where there is no absorption associated with the ac Hall conductivity in type-I semimetals and regions where it is instead constant for type-II semimetals. We comment on implications for the absorption of circularly polarized light.

AC impedance spectroscopy of NASICON type Na3Fe2(PO4)3 ceramic

NASA Astrophysics Data System (ADS)

Mandal, Biswajit; Thakur, A. K.

2018-05-01

Super ionic conductors (e.g.; A3M2(XO4)3, A=Li, Na) have received attention in applied research due to their interesting electrochemical property and inherently high ionic conductivity [1]. However, structural and compatibility requirements for fast ion transport is stringent and it plays a crucial role. In A3M2(XO4)3, a suitable cage formation in the crystal framework due to corner sharing arrangement of XO4 tetrahedra and MO6 octahedra creates voids that acts as host/guest site for cation transport. In this work, we report Nasicon structure Na3Fe2(PO4)3 (NFP) prepared via sol-gel route mediated by citric acid. Structural analysis confirmed that NFP sample belongs to monoclinic crystal structure having Cc space group (S. G. No 9) with lattice parameters, a=15.106 Å, b=8.722 Å, c=8.775 Å and β=124.96°. Electrical properties of the prepared sample have been studied by AC impedance spectroscopy technique. The AC conductivity results indicated typical signature of ionically conducting system.

Electric-Field-Directed Parallel Alignment Architecting 3D Lithium-Ion Pathways within Solid Composite Electrolyte.

PubMed

Liu, Xueqing; Peng, Sha; Gao, Shuyu; Cao, Yuancheng; You, Qingliang; Zhou, Liyong; Jin, Yongcheng; Liu, Zhihong; Liu, Jiyan

2018-05-09

It is of great significance to seek high-performance solid electrolytes via a facile chemistry and simple process for meeting the requirements of solid batteries. Previous reports revealed that ion conducting pathways within ceramic-polymer composite electrolytes mainly occur at ceramic particles and the ceramic-polymer interface. Herein, one facile strategy toward ceramic particles' alignment and assembly induced by an external alternating-current (AC) electric field is presented. It was manifested by an in situ optical microscope that Li 1.3 Al 0.3 Ti 1.7 (PO 4 ) 3 particles and poly(ethylene glycol) diacrylate in poly(dimethylsiloxane) (LATP@PEGDA@PDMS) assembled into three-dimensional connected networks on applying an external AC electric field. Scanning electron microscopy revealed that the ceramic LATP particles aligned into a necklacelike assembly. Electrochemical impedance spectroscopy confirmed that the ionic conductivity of this necklacelike alignment was significantly enhanced compared to that of the random one. It was demonstrated that this facile strategy of applying an AC electric field can be a very effective approach for architecting three-dimensional lithium-ion conductive networks within solid composite electrolyte.

AC/DC electrical conduction and dielectric properties of PMMA/PVAc/C60 down-shifting nanocomposite films

NASA Astrophysics Data System (ADS)

El-Bashir, S. M.; Alwadai, N. M.; AlZayed, N.

2018-02-01

Polymer nanocomposite films were prepared by doping fullerene C60 in polymer blend composed of polymethacrylate/polyvinyl acetate blends (PMMA/PVAc) using solution cast technique. The films were characterized by differential scanning calorimeter (DSC), Transmission electron microscope (TEM), DC/AC electrical conductivity and dielectric measurements in the frequency range (100 Hz- 1 MHz). The glass transition temperature, Tg, was increased by increasing the concentration of fullerene C60; this property reflects the increase of thermal stability by increasing the nanofiller content. The DC and AC electrical conductivities were enhanced by increasing C60 concentration due to the electron hopping or tunneling between filled and empty localized states above Tg. The relaxation time was determined from the αβ -relaxations and found to be attenuated by increasing the temperature as a typical behavior of amorphous polymers. The calculated values of thermodynamic parameters revealed the increase of molecular stability by increasing the doping concentration; this feature supports the application of PMMA/PVAc/C60 nanocomposite films in a wide scale of solar energy conversion applications such as luminescent down-shifting (LDS) coatings for photovoltaic cells.

Influence of reactivation on the electrochemical performances of activated carbon based on coconut shell.

PubMed

Geng, Xin; Li, Lixiang; Zhang, Meiling; An, Baigang; Zhu, Xiaoming

2013-12-01

Coconut shell-based activated carbon (AC) were prepared by CO2 activation, and then the ACs with higher mesopore ratio were obtained by steam activation and by impregnating iron catalyst followed by steam activation, respectively. The AC with the highest mesopore ratio (AChmr) shows superior capacitive behavior, power output and high-frequency performance in supercapacitors. The results should attribute to the connection of its wide micropores and mesopores larger than 3 nm, which is more favorable for fast ionic transportation. The pore size distribution exhibits that the mesopore ratios of the ACs are significantly increased by reactivation of steam or catalyst up to 75% and 78%, respectively. As evidenced by cyclic voltammetry, electrochemical impedance spectroscopy, and galvanostatic measurements, the AChmr shows superior capacitive behaviors, conductivity and performance of electrolytic ionic transportation. The response current densities are evidently enhanced through the cyclic voltammery test at 50 mV/sec scan rate. The electrochemical impedance spectroscopy demonstrates that the conductivity and ion transport performance of the ACs are improved. The specific capacitances of the ACs were increased from 140 to 240 F/g at 500 mA/g current density. The AChmr can provide much higher power density while still maintaining good energy density, and demonstrate excellent high-frequency performances. The pore structure and conductivity of the AChmr also improve the cycleability and self-discharge of supercapacitors. Such AChmr exhibits a great potential in supercapacitors, particularly for applications where high power output and good high-frequency capacitive performances are required. Copyright © 2013 The Research Centre for Eco-Environmental Sciences, Chinese Academy of Sciences. Published by Elsevier B.V. All rights reserved.

Frequency and phase effects on cervical vestibular evoked myogenic potentials (cVEMPs) to air-conducted sound.

PubMed

Govender, Sendhil; Dennis, Danielle L; Colebatch, James G

2016-09-01

Few previous studies of tuning using air-conducted (AC) stimuli and the cervical vestibular evoked myogenic potential (cVEMP) have compensated for the effects of middle ear (ME) attenuation. Zhang et al. (Exp Brain Res 213:111-116, 2011a) who did allow for ME effects were able to show a secondary peak around 100 Hz for the ocular VEMP (oVEMP). Recently, it has become clear that the otolith afferents responsible for the cVEMP and oVEMP differ and thus the nature of tuning may be more related to the reflex studied determining which otolith receptors are activated rather than the properties of the stimulus. We wished to reinvestigate the tuning for the cVEMP using AC stimuli, to establish whether the low-frequency peak is specific for the oVEMP or a consequence of the stimulus modality itself. In response to recent evidence using a 500 Hz AC stimulus that there was no effect of stimulus phase, we also investigated whether phase (condensation or rarefaction) had an effect at any frequency. We measured corrected cVEMP amplitudes and latencies in response to stimuli between 50 and 1200 Hz in 10 normal volunteers using an AC stimulus adjusted for ME attenuation. We confirmed earlier reports of the similarity of the tuning for both the cVEMP and oVEMP reflexes but found no separate 100 Hz peak for the cVEMP. AC stimulus phase did not affect either amplitude or latency. Both the tuning pattern and the phase effects contrast with those previously reported for bone-conducted (BC) stimuli. Unlike BC stimulation, which shows tuning consistent with an action on the otolith membrane, AC stimuli are likely to act through a different mechanism, most likely directly at the hair cell level.

Structural, microstructural and electrical characterization of BaSnO3 and Ba0.90Y0.10SnO3 synthesized by solution combustion method

NASA Astrophysics Data System (ADS)

Kumar, Upendra; Yadav, Dharmendra; Upadhyay, Shail; Thakur, Anukul K.

2018-04-01

Powder of perovskite oxides BaSnO3 and Ba0.90Y0.10SnO3 have been synthesized by solution combustion method. Rietveld profile analysis shows that the phases crystallize with cubic unit cell in the space group pm3m. Further purity of the synthesized powders was checked by Fourier transform of infrared (FTIR) spectroscopy. The average grain size of the sintered samples was obtained using Scanning electron microscopy (SEM) and found to be 4.9 and 2.8 1m for BaSnO3 and Ba0.90Y0.10SnO3, respectively. The AC conductivity (σac) of synthesized samples was measured in the frequency range from 24Hz-1MHz and temperature range 100 - 600°C. Conductivity spectra of both the samples followed universal Johnscher's power law at different temperatures. The value of bulk or dc conductivity (σdc) at different temperatures has been extracted by fitting the Johnscher's power law to AC conductivity spectra. The activation energy for σc has been obtained from the least square linear fit of data points and found to be 0.53 eV and 0.43 eV, respectively for BaSnO3 and Ba0.90Y0.10SnO3. Based on the value of activation energy it is proposed that conduction in these samples is govern via hopping of (OH)•. The value of conductivity at temperature 550°C of Ba0.90Y0.10SnO3 is 0.00406 S-cm-1 higher than BaSnO3 (0.00173 S-cm-1) at the same temperature.

Quantum-ring spin interference device tuned by quantum point contacts

DOE Office of Scientific and Technical Information (OSTI.GOV)

Diago-Cisneros, Leo; Mireles, Francisco

2013-11-21

We introduce a spin-interference device that comprises a quantum ring (QR) with three embedded quantum point contacts (QPCs) and study theoretically its spin transport properties in the presence of Rashba spin-orbit interaction. Two of the QPCs conform the lead-to-ring junctions while a third one is placed symmetrically in the upper arm of the QR. Using an appropriate scattering model for the QPCs and the S-matrix scattering approach, we analyze the role of the QPCs on the Aharonov-Bohm (AB) and Aharonov-Casher (AC) conductance oscillations of the QR-device. Exact formulas are obtained for the spin-resolved conductances of the QR-device as a functionmore » of the confinement of the QPCs and the AB/AC phases. Conditions for the appearance of resonances and anti-resonances in the spin-conductance are derived and discussed. We predict very distinctive variations of the QR-conductance oscillations not seen in previous QR proposals. In particular, we find that the interference pattern in the QR can be manipulated to a large extend by varying electrically the lead-to-ring topological parameters. The latter can be used to modulate the AB and AC phases by applying gate voltage only. We have shown also that the conductance oscillations exhibits a crossover to well-defined resonances as the lateral QPC confinement strength is increased, mapping the eigenenergies of the QR. In addition, unique features of the conductance arise by varying the aperture of the upper-arm QPC and the Rashba spin-orbit coupling. Our results may be of relevance for promising spin-orbitronics devices based on quantum interference mechanisms.« less

The electrical and dielectric properties of the Au/Ti/HfO2/n-GaAs structures

NASA Astrophysics Data System (ADS)

Karabulut, Abdulkerim; Türüt, Abdulmecit; Karataş, Şükrü

2018-04-01

In this work, temperature dependent electrical and dielectric properties of the Au/Ti/HfO2/n-GaAs structures were investigated using capacitance-voltage (C-V) and conductance-voltage (G-V) measurements in the temperature range of 60-320 K by steps of 20 K at 1 MHz. The dielectric constant (ε‧), dielectric loss (ε″), dielectric loss tangent (tanδ) and ac electrical conductivities (σac) have been calculated as a function of temperature. These values of the ε‧, ε″, tanδ and σac have been found to be 2.272, 5.981, 2.631 and 3.32 × 10-6 (Ω-1cm-1) at 80 K, respectively, 1.779, 2.315, 1.301 and 1.28 × 10-6 (Ω-1cm-1), respectively at 320 K. These decrease of the dielectric parameters (ε‧, ε″, tanδ and σac) have been observed at high temperatures. The experimental results show that electrical and dielectric properties are strongly temperature and bias voltage dependent.

Conductive paper fabricated by layer-by-layer assembly of polyelectrolytes and ITO nanoparticles

NASA Astrophysics Data System (ADS)

Peng, C. Q.; Thio, Y. S.; Gerhardt, R. A.

2008-12-01

A new salt-free approach was developed for fabricating conductive paper by layer-by-layer (LBL) assembly of conductive indium tin oxide (ITO) nanoparticles and polyelectrolytes onto wood fibers. Subsequent to the coating procedure, the fibers were manufactured into conductive paper using traditional paper making methods. The wood fibers were first coated with polyethyleneimine (PEI) and then LBL assembled with poly(sodium 4-styrenesulfonate) (PSS) and ITO for several bilayers. The surface charge intensity of both the ITO nanoparticles and the coated wood fibers were evaluated by measuring the ζ-potential of the nanoparticles and short fibers, respectively. The ITO nanoparticles were found to preferentially aggregate on defects on the fiber surfaces and formed interconnected paths, which led to the formation of conductive percolation paths throughout the whole paper. With ten bilayer coatings, the as-made paper was made DC conductive, and its σdc was measured to be 5.2 × 10-6 S cm-1 in the in-plane (IP) direction, while the conductivity was 1.9 × 10-8 S cm-1 in the through-the-thickness (TT) direction. The percolation phenomena in these LBL-assembled ITO-coated paper fibers was evaluated using scanning electron microscopy (SEM), current atomic force microscopy (I-AFM), and impedance measurements. The AC electrical properties are reported for frequencies ranging from 0.01 Hz to 1 MHz. A clear transition from insulating to conducting behavior is observed in the AC conductivity.

Influence of Ag, Cd or Pb Addition on Electrical and Dielectric Properties of Bulk Glassy Se-Ge

NASA Astrophysics Data System (ADS)

El-Metwally, E. G.; Shakra, A. M.

2018-05-01

Bulk glassy samples of Se0.7Ge0.3 and Se0.7Ge0.25 X 0.05 (X = Ag, Cd or Pb) chalcogenide glass have been prepared by melt-quenching method. The studied compositions were examined in powder form by x-ray diffraction analysis. The direct-current (dc) conductivity σ_{{dc}} was measured for bulk samples in the temperature range from 303 K to 433 K, revealing enhancement with temperature for all samples. The results indicate two values of activation energy ( Δ E_{{σ1 }} and Δ E_{{σ2 }} ) due to two conduction mechanisms. Measurements of the alternating-current (ac) conductivity σ_{{ac}} ( ω ) and dielectric properties for bulk samples were carried out in the temperature range from 303 K to 433 K and frequency range from 1 kHz to 1 MHz. The ac conductivity σ_{{ac}} ( ω ) was temperature dependent and proportional to ωS , where S is the frequency exponent, which reduced with rising temperature, and ω is the angular frequency. These results are discussed based on a correlated barrier hopping model. The calculated values of the maximum height of the barrier W_{{M}} for each composition are consistent with carrier hopping over a potential barrier. The density of localized states N( {E_{{F}} } ) at the Fermi level lay in the range from 1019 eV-1 cm-3 to 1020 eV-1 cm-3, and increased with temperature. The dielectric constant ɛ1 ( ω ) and loss ɛ2 ( ω ) increased with temperature but decreased with frequency. The values of σ_{{dc}} , σ_{{ac}} ( ω ) , ɛ1 ( ω ) , and ɛ2 ( ω ) increased with temperature and with addition of Ag, Cd or Pb. The observed increase was greater for Se0.7Ge0.25Pb0.05 than for Se0.7Ge0.25Cd0.05, which was greater than for Se0.7Ge0.25Ag0.05.

Ion Channel Conductance Measurements on a Silicon-Based Platform

DTIC Science & Technology

2006-01-01

calculated using the molecular dynamics code, GROMACS . Reasonable agreement is obtained in the simulated versus measured conductance over the range of...measurements of the lipid giga-seal characteristics have been performed, including AC conductance measurements and statistical analysis in order to...Dynamics kernel self-consistently coupled to Poisson equations using a P3M force field scheme and the GROMACS description of protein structure and

High frequency bone conduction auditory evoked potentials in the guinea pig: Assessing cochlear injury after ossicular chain manipulation.

PubMed

Bergin, M J; Bird, P A; Vlajkovic, S M; Thorne, P R

2015-12-01

Permanent high frequency (>4 kHz) sensorineural hearing loss following middle ear surgery occurs in up to 25% of patients. The aetiology of this loss is poorly understood and may involve transmission of supra-physiological forces down the ossicular chain to the cochlea. Investigating the mechanisms of this injury using animal models is challenging, as evaluating cochlear function with evoked potentials is confounded when ossicular manipulation disrupts the normal air conduction (AC) pathway. Bone conduction (BC) using clinical bone vibrators in small animals is limited by poor transducer output at high frequencies sensitive to trauma. The objectives of the present study were firstly to evaluate a novel high frequency bone conduction transducer with evoked auditory potentials in a guinea pig model, and secondly to use this model to investigate the impact of middle ear surgical manipulation on cochlear function. We modified a magnetostrictive device as a high frequency BC transducer and evaluated its performance by comparison with a calibrated AC transducer at frequencies up to 32 kHz using the auditory brainstem response (ABR), compound action potential (CAP) and summating potential (SP). To mimic a middle ear traumatising stimulus, a rotating bur was brought in to contact with the incudomalleal complex and the effect on evoked cochlear potentials was observed. BC-evoked potentials followed the same input-output function pattern as AC potentials for all ABR frequencies. Deterioration in CAP and SP thresholds was observed after ossicular manipulation. It is possible to use high frequency BC to evoke responses from the injury sensitive basal region of the cochlea and so not rely on AC with the potential confounder of conductive hearing loss. Ongoing research explores how these findings evolve over time, and ways in which injury may be reduced and the cochlea protected during middle ear surgery. Copyright © 2015 Elsevier B.V. All rights reserved.

Electrical Conductivity Mechanism in Unconventional Lead Vanadate Glasses

NASA Astrophysics Data System (ADS)

Abdel-Wahab, F.; Merazga, A.; Montaser, A. A.

2017-03-01

Lead vanadate glasses of the system (V2O5)_{1-x}(PbO)x with x = 0.4, 0.45, 0.5, 0.55, 0.6 have been prepared by the press-quenching technique. The dc (σ (0)) and ac (σ (ω )) electrical conductivities were measured in the temperature range from 150 to 420 K and the frequency range from 102 to 106 Hz. The electrical properties are shown to be sensitive to composition. The experimental results have been analyzed within the framework of different models. The dc conductivity is found to be proportional to Tp with the exponent p ranging from 8.2 to 9.8, suggesting that the transport is determined by a multi-phonon process of weak electron-lattice coupling. The ac conductivity is explained by the percolation path approximation (PPA). In this model, σ (ω ) is closely related to the σ (0) and fitting the experimental data produces a dielectric relaxation time τ in good agreement with the expected value in both magnitude and temperature dependence.

Attachment representations and socio-emotional difficulties in alternative care: A comparison between residential, foster and family based children in Chile.

PubMed

Garcia Quiroga, Manuela; Hamilton-Giachritsis, Catherine; Ibañez Fanés, Margarita

2017-08-01

Attachment has been assessed in children living in alternative care (AC) settings, such as Residential Homes (RC) and Foster Care (FC). However, no study has been conducted to compare attachment styles in residential, foster and parental care conducted as usual in the same country at the same point in time. There is also a lack of studies conducted in less developed countries. Therefore, the aim of this study was to compare outcomes for children living in three different types of care in Chile. Three groups of children (N=77), living in (RC), (FC) and with biological parents (PC) were compared. Attachment styles, Indiscriminate Friendliness (IF) and socio-emotional/behavioral difficulties were assessed. Higher rates of secure attachment were observed in the RC group (36.1%) when compared to studies in RC in other countries (mean 18%). However, children in both types of AC were significantly more likely to have insecure and/or disorganized attachment styles than PC children. Higher rates of socio-emotional and behavioral problems were observed in RC (55.6%) and FC (50%) compared to PC (10%). Within type of AC, no significant differences were found, for attachment styles or for socio-emotional/behavioral difficulties, the only difference were the levels of IF, with children in RC having higher levels. As a conclusion, impact of placement in AC can vary between different countries, other factors, rather than only type of AC could better explain differences in attachment security for children. Implications for research and practices are discussed. Copyright © 2017 Elsevier Ltd. All rights reserved.

Improved ionic conductivity of lithium-zinc-tellurite glass-ceramic electrolytes

NASA Astrophysics Data System (ADS)

Widanarto, W.; Ramdhan, A. M.; Ghoshal, S. K.; Effendi, M.; Cahyanto, W. T.; Warsito

An enhancement in the secondary battery safety demands the optimum synthesis of glass-ceramics electrolytes with modified ionic conductivity. To achieve improved ionic conductivity and safer operation of the battery, we synthesized Li2O included zinc-tellurite glass-ceramics based electrolytes of chemical composition (85-x)TeO2·xLi2O·15ZnO, where x = 0, 5, 10, 15 mol%. Samples were prepared using the melt quenching method at 800 °C followed by thermal annealing at 320 °C for 3 h and characterized. The effects of varying temperature, alternating current (AC) frequency and Li2O concentration on the structure and ionic conductivity of such glass-ceramics were determined. The SEM images of the annealed glass-ceramic electrolytes displayed rough surface with a uniform distribution of nucleated crystal flakes with sizes less than 1 μm. X-ray diffraction analysis confirmed the well crystalline nature of achieved electrolytes. Incorporation of Li2O in the electrolytes was found to generate some new crystalline phases including hexagonal Li6(TeO6), monoclinic Zn2Te3O8 and monoclinic Li2Te2O5. The estimated crystallite size of the electrolyte was ranged from ≈40 to 80 nm. AC impedance measurement revealed that the variation in the temperatures, Li2O contents, and high AC frequencies have a significant influence on the ionic conductivity of the electrolytes. Furthermore, electrolyte doped with 15 mol% of Li2O exhibited the optimum performance with an ionic conductivity ≈2.4 × 10-7 S cm-1 at the frequency of 54 Hz and in the temperature range of 323-473 K. This enhancement in the conductivity was attributed to the sizable alteration in the ions vibration and ruptures of covalent bonds in the electrolytes network structures.

Structural, optical and ac electrical characterization of CBD synthesized NiO thin films: Influence of thickness

NASA Astrophysics Data System (ADS)

Das, M. R.; Mukherjee, A.; Mitra, P.

2017-09-01

We have studied the electrical conductivity, dielectric relaxation mechanism and impedance spectroscopy characteristics of nickel oxide (NiO) thin films synthesized by chemical bath deposition (CBD) method. Thickness dependent structural, optical and ac electrical characterization has been carried out and deposition time was varied to control the thickness. The material has been characterized using X-ray diffraction and UV-VIS spectrophotometer. Impedance spectroscopy analysis confirmed enhancement of ac conductivity and dielectric constant for films deposited with higher deposition time. Decrease of grain size in thicker films were confirmed from XRD analysis and activation energy of the material for electrical charge hopping process was increased with thickness of the film. Decrease in band gap in thicker films were observed which could be associated with creation of additional energy levels in the band gap of the material. Cole-Cole plot shows contribution of both grain and grain boundary towards total resistance and capacitance. The overall resistance was found to decrease from 14.6 × 105 Ω for 30 min deposited film ( 120 nm thick) to 2.42 × 105 Ω for 120 min deposited film ( 307 nm thick). Activation energy value to electrical conduction process evaluated from conductivity data was found to decrease with thickness. Identical result was obtained from relaxation time approach suggesting hopping mechanism of charge carriers.

The effect of superior canal dehiscence on cochlear potential in response to air-conducted stimuli in chinchilla

PubMed Central

Songer, Jocelyn E.; Rosowski, John J.

2006-01-01

A superior semicircular canal dehiscence (SCD) is a break or hole in the bony wall of the superior semicircular canal. Patients with SCD syndrome present with a variety of symptoms: some with vestibular symptoms, others with auditory symptoms (including low-frequency conductive hearing loss) and yet others with both. We are interested in whether or not mechanically altering the superior canal by introducing a dehiscence is sufficient to cause the low-frequency conductive hearing loss associated with SCD syndrome. We evaluated the effect of a surgically introduced dehiscence on auditory responses to air-conducted (AC) stimuli in 11 chinchilla ears. Cochlear potential (CP) was recorded at the round-window before and after a dehiscence was introduced. In each ear, a decrease in CP in response to low frequency (<2 kHz) sound stimuli was observed after the introduction of the dehiscence. The dehiscence was then patched with cyanoacrylate glue leading to a reversal of the dehiscence-induced changes in CP. The reversible decrease in auditory sensitivity observed in chinchilla is consistent with the elevated AC thresholds observed in patients with SCD. According to the ‘third-window’ hypothesis the SCD shunts sound-induced stapes velocity away from the cochlea, resulting in decreased auditory sensitivity to AC sounds. The data collected in this study are consistent with predictions of this hypothesis. PMID:16150562

On the inhibition of muscle membrane chloride conductance by aromatic carboxylic acids

PubMed Central

Palade, PT; Barchi, RL

1977-01-01

25 aromatic carboxylic acids which are analogs of benzoic acid were tested in the rat diaphragm preparation for effects on chloride conductance (G(Cl)). Of the 25, 19 were shown to reduce membrane G(Cl) with little effect on other membrane parameters, although their apparent K(i) varied widely. This inhibition was reversible if exposure times were not prolonged. The most effective analog studied was anthracene-9-COOH (9-AC; K(i) = 1.1 x 10(-5) M). Active analogs produced concentration-dependent inhibition of a type consistent with interaction at a single site or group of sites having similar binding affinities, although a correlation could also be shown between lipophilicity and K(i). Structure-activity analysis indicated that hydrophobic ring substitution usually increased inhibitory activity while para polar substitutions reduced effectiveness. These compounds do not appear to inhibit G(Cl) by altering membrane surface charge and the inhibition produced is not voltage dependent. Qualitative characteristics of the I-V relationship for Cl(-) current are not altered. Conductance to all anions is not uniformly altered by these acids as would be expected from steric occlusion of a common channel. Concentrations of 9-AC reducing G(Cl) by more than 90 percent resulted in slight augmentation of G(I). The complete conductance sequence obtained at high levels of 9-AC was the reverse of that obtained under control conditions. Permeability sequences underwent progressive changes with increasing 9-AC concentration and ultimately inverted at high levels of the analog. Aromatic carboxylic acids appear to inhibit G(Cl) by binding to a specific intramembrane site and altering the selectivity sequence of the membrane anion channel. PMID:894246

Measuring skin conductance over clothes.

PubMed

Hong, Ki Hwan; Lee, Seung Min; Lim, Yong Gyu; Park, Kwang Suk

2012-11-01

We propose a new method that measures skin conductance over clothes to nonintrusively monitor the changes in physiological conditions affecting skin conductance during daily activities. We selected the thigh-to-thigh current path and used an indirectly coupled 5-kHz AC current for the measurement. While varying the skin conductance by the Valsalva maneuver method, the results were compared with the traditional galvanic skin response (GSR) measured directly from the fingers. Skin conductance measured using a 5-kHz current displayed a highly negative correlation with the traditional GSR and the current measured over clothes reflected the rate of change of the conductance of the skin beneath.

47 CFR 15.212 - Modular transmitters.

Code of Federal Regulations, 2013 CFR

2013-10-01

... 47 Telecommunication 1 2013-10-01 2013-10-01 false Modular transmitters. 15.212 Section 15.212 Telecommunication FEDERAL COMMUNICATIONS COMMISSION GENERAL RADIO FREQUENCY DEVICES Intentional Radiators § 15.212... powered, it must comply with the AC line conducted requirements found in § 15.207. AC or DC power lines...

47 CFR 15.212 - Modular transmitters.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 47 Telecommunication 1 2010-10-01 2010-10-01 false Modular transmitters. 15.212 Section 15.212 Telecommunication FEDERAL COMMUNICATIONS COMMISSION GENERAL RADIO FREQUENCY DEVICES Intentional Radiators § 15.212... powered, it must comply with the AC line conducted requirements found in § 15.207. AC or DC power lines...

47 CFR 15.212 - Modular transmitters.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 47 Telecommunication 1 2011-10-01 2011-10-01 false Modular transmitters. 15.212 Section 15.212 Telecommunication FEDERAL COMMUNICATIONS COMMISSION GENERAL RADIO FREQUENCY DEVICES Intentional Radiators § 15.212... powered, it must comply with the AC line conducted requirements found in § 15.207. AC or DC power lines...

47 CFR 15.212 - Modular transmitters.

Code of Federal Regulations, 2012 CFR

2012-10-01

... 47 Telecommunication 1 2012-10-01 2012-10-01 false Modular transmitters. 15.212 Section 15.212 Telecommunication FEDERAL COMMUNICATIONS COMMISSION GENERAL RADIO FREQUENCY DEVICES Intentional Radiators § 15.212... powered, it must comply with the AC line conducted requirements found in § 15.207. AC or DC power lines...

47 CFR 15.212 - Modular transmitters.

Code of Federal Regulations, 2014 CFR

2014-10-01

... 47 Telecommunication 1 2014-10-01 2014-10-01 false Modular transmitters. 15.212 Section 15.212 Telecommunication FEDERAL COMMUNICATIONS COMMISSION GENERAL RADIO FREQUENCY DEVICES Intentional Radiators § 15.212... powered, it must comply with the AC line conducted requirements found in § 15.207. AC or DC power lines...

Effect of electric field induced alignment and dispersion of functionalized carbon nanotubes on properties of natural rubber

NASA Astrophysics Data System (ADS)

Gao, Jiangshan; He, Yan; Gong, Xiubin

2018-06-01

The original equipment and method for orienting multi-walled carbon nanotubes (MWCNTs) in natural rubber (NR) by alternating current (AC) electric field were reported in the present study. MWCNTs with various volume fractions were dispersed in the mixture latex which composed of natural rubber, additives and methylbenzene. The application of AC electric field during nanocomposites curing process was used to induce the formation of aligned conductive nanotube networks between the electrodes. The aligned MWCNTs in the composites have a better orientation performance and dispersion quality than these of random MWCNTs by analyzing TEM and SEM images. The effects of MWCNTs anisotropy on thermal conductivity, dielectric properties, and dynamic mechanical properties of NR were studied. The mean value of thermal conductivity of composites loading with aligned MWCNTs was 8.67% higher than that of composites with random MWCNTs due to the anisotropy of aligned MWCNTs. The compounds with aligned MWCNTs possessed low dielectric constant, loss tangents and conductivity, namely a good insulativity. The compounds loading with aligned MWCNTs had lower loss modulus and better dynamic mechanical properties than those with random MWCNTs. This method can make full use of the high thermal conductivity of MWCNTs axis, and expand the application areas of natural rubber like conducting heat in a certain direction with a high efficiency.

Electrical, dielectric properties and study of AC electrical conduction mechanism of Li0.9□0.1NiV0.5P0.5O4

NASA Astrophysics Data System (ADS)

Rahal, A.; Borchani, S. Megdiche; Guidara, K.; Megdiche, M.

2018-02-01

In this paper, we report the measurements of impedance spectroscopy for a new olivine-type lithium deficiency Li0.9□0.1NiV0.5P0.5O4 compound. It was synthesized by the conventional solid-state technique. All the X-ray diffraction peaks of the compound are indexed, and it is found that the sample is well crystallized in orthorhombic olivine structure belonging to the space group Pnma. Conductivity and dielectric analyses of the sample are carried out at different temperatures and frequencies using the complex impedance spectroscopy technique. The electrical conductivity of Li0.9□0.1NiV0.5P0.5O4 is higher than that of parent compound LiNiV0.5P0.5O4. Temperature dependence of the DC conductivity and modulus was found to obey the Arrhenius law. The obtained values of activation energy are different which confirms that transport in the title compound is not due to a simple hopping mechanism. To determine the conduction mechanism, the AC conductivity and its frequency exponent have been analysed in this work by a theoretical model based on quantum mechanical tunnelling: the non-overlapping small polaron tunnelling model.

AC conductivity, magnetic and shielding effectiveness studies on polyaniline embedded Co0.5Mn0.5Fe2O4 nanoparticles for electromagnetic interference suppression

NASA Astrophysics Data System (ADS)

Gurusiddesh, M.; Madhu, B. J.; Shankaramurthy, G. J.

2018-05-01

Electrically conducting Polyaniline (PANI)/Co0.5Mn0.5Fe2O4 nanocomposites are synthesized by in situ polymerization of aniline monomer in the presence of Co0.5Mn0.5Fe2O4 nanoparticles. Structural studies on the synthesized samples have been carried out using X-ray diffraction technique, Field emission scanning electron microscopy and Energy dispersive X-ray spectroscopy. Frequency dependent ac conductivity studies on the prepared samples revealed that conductivity of the composite is high compared to Co0.5Mn0.5Fe2O4 nanoparticles. Further, both the samples exhibited hysteresis behavior under the applied magnetic field. Electromagnetic interference (EMI) shielding effectiveness of both the samples decreases with increase in the applied frequency in the studied frequency range. Maximum shielding effectiveness (SE) of 31.49 dB and 62.84 dB were obtained for Co0.5Mn0.5Fe2O4 nanoparticles and PANI/Co0.5Mn0.5Fe2O4 nanocomposites respectively in the studied frequency range. Observed higher EMI shielding in the composites was attributed to its high electrical conductivity.

Cole-cole analysis and electrical conduction mechanism of N{sup +} implanted polycarbonate

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chawla, Mahak; Shekhawat, Nidhi; Aggarwal, Sanjeev, E-mail: write2sa@gmail.com

2014-05-14

In this paper, we present the analysis of the dielectric (dielectric constant, dielectric loss, a.c. conductivity) and electrical properties (I–V characteristics) of pristine and nitrogen ion implanted polycarbonate. The samples of polycarbonate were implanted with 100 keV N{sup +} ions with fluence ranging from 1 × 10{sup 15} to 1 × 10{sup 17} ions cm{sup −2}. The dielectric measurements of these samples were performed in the frequency range of 100 kHz to 100 MHz. It has been observed that dielectric constant decreases whereas dielectric loss and a.c. conductivity increases with increasing ion fluence. An analysis of real and imaginary parts of dielectric permittivity has beenmore » elucidated using Cole-Cole plot of the complex permittivity. With the help of Cole-Cole plot, we determined the values of static dielectric constant (ε{sub s}), optical dielectric constant (ε{sub ∞}), spreading factor (α), average relaxation time (τ{sub 0}), and molecular relaxation time (τ). The I–V characteristics were studied using Keithley (6517) electrometer. The electrical conduction behaviour of pristine and implanted polycarbonate specimens has been explained using various models of conduction.« less

Dynamics and relaxation of charge carriers in poly(methylmethacrylate)-lithium salt based polymer electrolytes plasticized with ethylene carbonate

NASA Astrophysics Data System (ADS)

Pal, P.; Ghosh, A.

2016-07-01

In this paper, we have studied the dynamics and relaxation of charge carriers in poly(methylmethacrylate)-lithium salt based polymer electrolytes plasticized with ethylene carbonate. Structural and thermal properties have been examined using X-ray diffraction and differential scanning calorimetry, respectively. We have analyzed the complex conductivity spectra by using power law model coupled with the contribution of electrode polarization at low frequencies and high temperatures. The temperature dependence of the ionic conductivity and crossover frequency exhibits Vogel-Tammann-Fulcher type behavior indicating a strong coupling between the ionic and the polymer chain segmental motions. The scaling of the ac conductivity indicates that relaxation dynamics of charge carriers follows a common mechanism for all temperatures and ethylene carbonate concentrations. The analysis of the ac conductivity also shows the existence of a nearly constant loss in these polymer electrolytes at low temperatures and high frequencies. The fraction of free anions and ion pairs in polymer electrolyte have been obtained from the analysis of Fourier transform infrared spectra. It is observed that these quantities influence the behavior of the composition dependence of the ionic conductivity.

Dynamics and relaxation of charge carriers in poly(methylmethacrylate)-lithium salt based polymer electrolytes plasticized with ethylene carbonate

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pal, P.; Ghosh, A., E-mail: sspag@iacs.res.in

2016-07-28

In this paper, we have studied the dynamics and relaxation of charge carriers in poly(methylmethacrylate)-lithium salt based polymer electrolytes plasticized with ethylene carbonate. Structural and thermal properties have been examined using X-ray diffraction and differential scanning calorimetry, respectively. We have analyzed the complex conductivity spectra by using power law model coupled with the contribution of electrode polarization at low frequencies and high temperatures. The temperature dependence of the ionic conductivity and crossover frequency exhibits Vogel-Tammann-Fulcher type behavior indicating a strong coupling between the ionic and the polymer chain segmental motions. The scaling of the ac conductivity indicates that relaxation dynamicsmore » of charge carriers follows a common mechanism for all temperatures and ethylene carbonate concentrations. The analysis of the ac conductivity also shows the existence of a nearly constant loss in these polymer electrolytes at low temperatures and high frequencies. The fraction of free anions and ion pairs in polymer electrolyte have been obtained from the analysis of Fourier transform infrared spectra. It is observed that these quantities influence the behavior of the composition dependence of the ionic conductivity.« less

Atomistic interpretation of the ac-dc crossover frequency in crystalline and glassy ionic conductors

NASA Astrophysics Data System (ADS)

Marple, M. A. T.; Avila-Paredes, H.; Kim, S.; Sen, S.

2018-05-01

A comprehensive analysis of the ionic dynamics in a wide variety of crystalline and glassy ionic conductors, obtained in recent studies using a combination of electrochemical impedance and nuclear magnetic resonance spectroscopic techniques, is presented. These results demonstrate that the crossover frequency, between the frequency-independent dc conductivity and the frequency-dependent ac conductivity, corresponds to the time scale of "successful" diffusive hops of the mobile ions between the trapping sites in the structure. These inter-site hops are typically compound in nature and consist of several elementary hops in the intervening region between the neighboring trapping sites.

Atomistic interpretation of the ac-dc crossover frequency in crystalline and glassy ionic conductors.

PubMed

Marple, M A T; Avila-Paredes, H; Kim, S; Sen, S

2018-05-28

A comprehensive analysis of the ionic dynamics in a wide variety of crystalline and glassy ionic conductors, obtained in recent studies using a combination of electrochemical impedance and nuclear magnetic resonance spectroscopic techniques, is presented. These results demonstrate that the crossover frequency, between the frequency-independent dc conductivity and the frequency-dependent ac conductivity, corresponds to the time scale of "successful" diffusive hops of the mobile ions between the trapping sites in the structure. These inter-site hops are typically compound in nature and consist of several elementary hops in the intervening region between the neighboring trapping sites.

Reversible Control of Anisotropic Electrical Conductivity using Colloidal Microfluidic Networks

DTIC Science & Technology

2007-04-17

field with the induced charges on each electrode result in AC electroosmotic force and steady fluid flow (nonzero time averaged) with a velocity...direction of the AC electroosmotic force (flow is unidirectional). From the work of Green and co- workers, we can write the particle displacement due to... AC voltage-frequency phase space allows us to probe a wide range of colloidal configurations that resemble “capacitive” and “resistive” networks in

Electrolyte Engineering: Optimizing High-Rate Double-Layer Capacitances of Micropore- and Mesopore-Rich Activated Carbon.

PubMed

Chen, Ting-Hao; Yang, Cheng-Hsien; Su, Ching-Yuan; Lee, Tai-Chou; Dong, Quan-Feng; Chang, Jeng-Kuei

2017-09-22

Various types of electrolyte cations as well as binary cations are used to optimize the capacitive performance of activated carbon (AC) with different pore structures. The high-rate capability of micropore-rich AC, governed by the mobility of desolvated cations, can outperform that of mesopore-rich AC, which essentially depends on the electrolyte conductivity. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

AC-Induced Bias Potential Effect on Corrosion of Steels

DTIC Science & Technology

2009-02-05

induction, variable conduction Experimental Setup Super- martensitic stainless steel composition Analysis: C Mn Si Cr Ni Mo Cu N Typical 13 Cr ɘ.01 0.6... stainless steel used in pipelines. •Low carbon (ɘ.01): allows the formation of a “soft” martensite that is more resistant than standard martensitic ...Proposed AC Corrosion Models  AC Simulated Corrosion testing  Stainless steel pipe and coating  Cathodic protection  Experimental Setup  Preliminary

An AC-electromagnetic bearing for flywheel energy storage in space

NASA Technical Reports Server (NTRS)

Nikolajsen, Jorgen L.

1993-01-01

A repulsive type AC-electromagnetic bearing was developed and tested. It was conceived on the basis of the so-called Magnetic River suspension for high-speed trains. The appearance of the bearing is similar to the traditional DC-type electromagnetic bearing but the operating principle is different. The magnets are fed with alternating current instead of direct current and the rotor is fitted with a conducting sleeve (e.g. aluminum) instead of a ferromagnetic sleeve. The repulsion is due to induction of eddy-currents in the conducting sleeve. The bearing is inherently stable and requires no feedback control. It provides support in five degrees of freedom such that a short rotor may be fully supported by a single bearing. These capabilities were demonstrated experimentally. On the down side, the load carrying capacity and the damping obtained so far were quite low compared to the DC-type bearing. Also, significant heating of the conducting sleeve was experienced. The AC-bearing is essentially a modified induction motor and there are strong indications that it can be run both as a motor and as a generator with no commutator requirements. It is therefore considered to be a good candidate for support of energy storage flywheels in space.

Development of a Bone-Conducted Ultrasonic Hearing Aid for the Profoundly Deaf: Evaluation of Sound Quality Using a Semantic Differential Method

NASA Astrophysics Data System (ADS)

Nakagawa, Seiji; Fujiyuki, Chika; Kagomiya, Takayuki

2013-07-01

Bone-conducted ultrasound (BCU) is perceived even by the profoundly sensorineural deaf. A novel hearing aid using the perception of amplitude-modulated BCU (BCU hearing aid: BCUHA) has been developed. However, there is room for improvement particularly in terms of sound quality. BCU speech is accompanied by a strong high-pitched tone and contain some distortion. In this study, the sound quality of BCU speech with several types of amplitude modulation [double-sideband with transmitted carrier (DSB-TC), double-sideband with suppressed carrier (DSB-SC), and transposed modulations] and air-conducted (AC) speech was quantitatively evaluated using semantic differential and factor analysis. The results showed that all the types of BCU speech had higher metallic and lower esthetic factor scores than AC speech. On the other hand, transposed speech was closer than the other types of BCU speech to AC speech generally; the transposed speech showed a higher powerfulness factor score than the other types of BCU speech and a higher esthetic factor score than DSB-SC speech. These results provide useful information for further development of the BCUHA.

Dielectric and electrical studies of PVC-PPy blends in dilute solution of THF

NASA Astrophysics Data System (ADS)

Sharma, Deepika; Tripathi, Deepti

2018-05-01

An influence of adding Polypyrrole (PPy) which is an intrinsically conducting polymer (ICP), on the dielectric dispersion behavior of Polyvinyl chloride (PVC) in dilute solution of Tetrahydrofuran (THF) at low frequency is reported. The blends of PVC with PPy forms colloidal suspension in THF. The dielectric dispersion study of PVC-PPy blends in THF has been carried out in the frequency range of 20 Hz to 2 MHz at temperature of 303K. The effect of increasing PPy concentration on dielectric and electrical parameters such as complex dielectric function [ɛ*(ω)], loss tangent [tan δ], complex electric modulus [M*(ω)], ac conductivity [σac], and complex impedance [Z*(ω)] of PVC - PPy blends in THF solution were studied. The electrode polarization and ionic conduction appears to have dominant influence on the complex dielectric constant in the low frequency region. The relaxation time values corresponding to these two phenomena are also reported.

Temperature-dependent ac conductivity and dielectric response of vanadium doped CaCu3Ti4O12 ceramic

NASA Astrophysics Data System (ADS)

Sen, A.; Maiti, U. N.; Thapa, R.; Chattopadhyay, K. K.

2011-09-01

Successful incorporation of vanadium dopant within the giant dielectric material CaCu 3Ti 4O12 (CCTO) through a conventional solid-state sintering process is achieved and its influence on the dielectric as well as electrical properties as a function of temperature and frequency is reported here. Proper crystalline phase formation together with dopant induced lattice constant shrinkage was confirmed through X-ray diffraction. The temperature dependence of the dielectric constant at different constant frequencies was investigated. We infer that the correlated barrier hopping (CBH) model is dominant in the conduction mechanism of the ceramic as per the temperature-dependent ac conductivity measurements. The electronic parameters such as density of the states at the Fermi level, N( E f) and hopping distance, R ω of the ceramic were also calculated using this model.

SR 85 and 77th Special Forces Way West McWhorter Rd Overpass Environmental Assessment

DTIC Science & Technology

2010-06-04

Evaluation criteria were developed and used to evaluate the potential impacts of the interchange alternatives. The evaluation matrix is in a chart...Land Use 6.8 ac taken 17.25 ac taken 34.80 ac taken 27.87 ac taken 35.25 ac taken Safety Stoplight has increased the potential for high speed...change in land  use  in  the easement. The Air Force would conduct further analysis for  potential  land  use  impacts –  Environmental Baseline Study or

Analytical theory and possible detection of the ac quantum spin Hall effect

DOE PAGES

Deng, W. Y.; Ren, Y. J.; Lin, Z. X.; ...

2017-07-11

Here, we develop an analytical theory of the low-frequency ac quantum spin Hall (QSH) effect based upon the scattering matrix formalism. It is shown that the ac QSH effect can be interpreted as a bulk quantum pumping effect. When the electron spin is conserved, the integer-quantized ac spin Hall conductivity can be linked to the winding numbers of the reflection matrices in the electrodes, which also equal to the bulk spin Chern numbers of the QSH material. Furthermore, a possible experimental scheme by using ferromagnetic metals as electrodes is proposed to detect the topological ac spin current by electrical means.

Deformation of giant vesicles in AC electric fields —Dependence of the prolate-to-oblate transition frequency on vesicle radius

NASA Astrophysics Data System (ADS)

Antonova, K.; Vitkova, V.; Mitov, M. D.

2010-02-01

The electrodeformation of giant vesicles is studied as a function of their radii and the frequency of the applied AC field. At low frequency the shape is prolate, at sufficiently high frequency it is oblate and at some frequency, fc, the shape changes from prolate to oblate. A linear dependence of the prolate-to-oblate transition inverse frequency, 1/fc, on the vesicle radius is found. The nature of this phenomenon does not change with the variation of both the solution conductivity, σ, and the type of the fluid enclosed by the lipid membrane (water, sucrose or glucose aqueous solution). When σ increases, the value of fc increases while the slope of the line 1/fc(r) decreases. For vesicles in symmetrical conditions (the same conductivity of the inner and the outer solution) a linear dependence between σ and the critical frequency, fc, is obtained for conductivities up to σ=114 μS/cm. For vesicles with sizes below a certain minimum radius, depending on the solution conductivity, no shape transition could be observed.

Binaural Hearing Ability With Bilateral Bone Conduction Stimulation in Subjects With Normal Hearing: Implications for Bone Conduction Hearing Aids.

PubMed

Zeitooni, Mehrnaz; Mäki-Torkko, Elina; Stenfelt, Stefan

The purpose of this study is to evaluate binaural hearing ability in adults with normal hearing when bone conduction (BC) stimulation is bilaterally applied at the bone conduction hearing aid (BCHA) implant position as well as at the audiometric position on the mastoid. The results with BC stimulation are compared with bilateral air conduction (AC) stimulation through earphones. Binaural hearing ability is investigated with tests of spatial release from masking and binaural intelligibility level difference using sentence material, binaural masking level difference with tonal chirp stimulation, and precedence effect using noise stimulus. In all tests, results with bilateral BC stimulation at the BCHA position illustrate an ability to extract binaural cues similar to BC stimulation at the mastoid position. The binaural benefit is overall greater with AC stimulation than BC stimulation at both positions. The binaural benefit for BC stimulation at the mastoid and BCHA position is approximately half in terms of decibels compared with AC stimulation in the speech based tests (spatial release from masking and binaural intelligibility level difference). For binaural masking level difference, the binaural benefit for the two BC positions with chirp signal phase inversion is approximately twice the benefit with inverted phase of the noise. The precedence effect results with BC stimulation at the mastoid and BCHA position are similar for low frequency noise stimulation but differ with high-frequency noise stimulation. The results confirm that binaural hearing processing with bilateral BC stimulation at the mastoid position is also present at the BCHA implant position. This indicates the ability for binaural hearing in patients with good cochlear function when using bilateral BCHAs.

[Inferior vestibular neuritis: diagnosis using VEMP].

PubMed

Walther, L E; Repik, I

2012-02-01

Vestibular evoked myogenic potentials (VEMP) are a new method to establish the functional status of the otolith organs. The sacculocollic reflex of the cervical VEMP to air conduction (AC) reflects predominantly saccular function due to saccular afferents to the inferior vestibular nerve. We describe a case of inferior vestibular neuritis as a rare differential diagnosis of vestibular neuritis. Clinical signs were a normal caloric response, unilaterally absent AC cVEMPs and bilaterally preserved ocular VEMPs (AC oVEMPs).

Gas exchange by the mesic-origin, arid land plantation species Robinia pseudoacacia under annual summer reduction in plant hydraulic conductance.

PubMed

Miyazawa, Yoshiyuki; Du, Sheng; Taniguchi, Takeshi; Yamanaka, Norikazu; Kumagai, Tomo'omi

2018-03-28

The mesic-origin plantation species Robinia pseudoacacia L. has been successfully grown in many arid land plantations around the world but often exhibits dieback and reduced growth due to drought. Therefore, to explore the behavior of this species under changing environmental conditions, we examined the relationship between ecophysiological traits, gas exchange and plant hydraulics over a 3-year period in trees that experienced reduced plant hydraulic conductance (Gp) in summer. We found that the transpiration rate, stomatal conductance (Gs) and minimum leaf water potential (Ψlmin) decreased in early summer in response to a decrease in Gp, and that Gp did not recover until the expansion of new leaves in spring. However, we did not observe any changes in the leaf area index or other ecophysiological traits at the leaf level in response to this reduction in Gp. Furthermore, model simulations based on measured data revealed that the canopy-scale photosynthetic rate (Ac) was 15-25% higher than the simulated Ac when it was assumed that Ψlmin remained constant after spring but almost the same as the simulated Ac when it was assumed that Gp remained high even after spring. These findings indicate that R. pseudoacacia was frequently exposed to a reduced Gp at the study site but offset its effects on Ac by plastically lowering Ψlmin to avoid experiencing any further reduction in Gp or Gs.

Evaluation of Bt Corn with Pyramided Genes on Efficacy and Insect Resistance Management for the Asian Corn Borer in China.

PubMed

Jiang, Fan; Zhang, Tiantao; Bai, Shuxiong; Wang, Zhenying; He, Kanglai

2016-01-01

A Bt corn hybrid (AcIe) with two Bt genes (cry1Ie and cry1Ac) was derived by breeding stack from line expressing Cry1Ie and a line expressing Cry1Ac. Efficacy of this pyramided Bt corn hybrid against the Asian corn borer (ACB), Ostrinia furnacalis, was evaluated. We conducted laboratory bioassays using susceptible and resistant ACB strains fed on artificial diet or fresh plant tissues. We also conducted field trials with artificial infestations of ACB neonates at the V6 and silk stages. The toxin-diet bioassay data indicated that mixtures of Cry1Ac and Cry1Ie proteins had synergistic insecticidal efficacy. The plant tissue bioassay data indicated that Bt corn hybrids expressing either a single toxin (Cry1Ac or Cry1Ie) or two toxins had high efficacy against susceptible ACB. Damage ratings in the field trials indicated that the Bt corn hybrids could effectively protect against 1st and the 2nd generation ACB in China. The hybrid line with two Bt genes showed a higher efficacy against ACB larvae resistant to Cry1Ac or CryIe than the hybrid containing one Bt gene, and the two gene hybrid would have increased potential for managing or delaying the evolution of ACB resistance to Bt corn plants.

A randomized controlled, non-inferiority trial of modified natural versus artificial cycle for cryo-thawed embryo transfer.

PubMed

Groenewoud, E R; Cohlen, B J; Al-Oraiby, A; Brinkhuis, E A; Broekmans, F J M; de Bruin, J P; van den Dool, G; Fleisher, K; Friederich, J; Goddijn, M; Hoek, A; Hoozemans, D A; Kaaijk, E M; Koks, C A M; Laven, J S E; van der Linden, P J Q; Manger, A P; Slappendel, E; Spinder, T; Kollen, B J; Macklon, N S

2016-07-01

Are live birth rates (LBRs) after artificial cycle frozen-thawed embryo transfer (AC-FET) non-inferior to LBRs after modified natural cycle frozen-thawed embryo transfer (mNC-FET)? AC-FET is non-inferior to mNC-FET with regard to LBRs, clinical and ongoing pregnancy rates (OPRs) but AC-FET does result in higher cancellation rates. Pooling prior retrospective studies of AC-FET and mNC-FET results in comparable pregnancy and LBRs. However, these results have not yet been confirmed by a prospective randomized trial. In this non-inferiority prospective randomized controlled trial (acronym 'ANTARCTICA' trial), conducted from February 2009 to April 2014, 1032 patients were included of which 959 were available for analysis. The primary outcome of the study was live birth. Secondary outcomes were clinical and ongoing pregnancy, cycle cancellation and endometrium thickness. A cost-efficiency analysis was performed. This study was conducted in both secondary and tertiary fertility centres in the Netherlands. Patients included in this study had to be 18-40 years old, had to have a regular menstruation cycle between 26 and 35 days and frozen-thawed embryos to be transferred had to derive from one of the first three IVF or IVF-ICSI treatment cycles. Patients with a uterine anomaly, a contraindication for one of the prescribed medications in this study or patients undergoing a donor gamete procedure were excluded from participation. Patients were randomized based on a 1:1 allocation to either one cycle of mNC-FET or AC-FET. All embryos were cryopreserved using a slow-freeze technique. LBR after mNC-FET was 11.5% (57/495) versus 8.8% in AC-FET (41/464) resulting in an absolute difference in LBR of -0.027 in favour of mNC-FET (95% confidence interval (CI) -0.065-0.012; P = 0.171). Clinical pregnancy occurred in 94/495 (19.0%) patients in mNC-FET versus 75/464 (16.0%) patients in AC-FET (odds ratio (OR) 0.8, 95% CI 0.6-1.1, P = 0.25). 57/495 (11.5%) mNC-FET resulted in ongoing pregnancy versus 45/464 (9.6%) AC-FET (OR 0.7, 95% CI 0.5-1.1, P = 0.15). χ(2) test confirmed the lack of superiority. Significantly more cycles were cancelled in AC-FET (124/464 versus 101/495, OR 1.4, 95% CI 1.1-1.9, P = 0.02). The costs of each of the endometrial preparation methods were comparable (€617.50 per cycle in NC-FET versus €625.73 per cycle in AC-FET, P = 0.54). The minimum of 1150 patients required for adequate statistical power was not achieved. Moreover, LBRs were lower than anticipated in the sample size calculation. LBRs after AC-FET were not inferior to those achieved by mNC-FET. No significant differences in clinical and OPR were observed. The costs of both treatment approaches were comparable. An educational grant was received during the conduct of this study. Merck Sharpe Dohme had no influence on the design, execution and analyses of this study. E.R.G. received an education grant by Merck Sharpe Dohme (MSD) during the conduct of the present study. B.J.C. reports grants from MSD during the conduct of the study. A.H. reports grants from MSD and Ferring BV the Netherlands and personal fees from MSD. Grants from ZonMW, the Dutch Organization for Health Research and Development. J.S.E.L. reports grants from Ferring, MSD, Organon, Merck Serono and Schering-Plough during the conduct of the study. F.J.M.B. receives monetary compensation as member of the external advisory board for Merck Serono, consultancy work for Gedeon Richter, educational activities for Ferring BV, research cooperation with Ansh Labs and a strategic cooperation with Roche on automated anti Mullerian hormone assay development. N.S.M. reports receiving monetary compensations for external advisory and speaking work for Ferring BV, MSD, Anecova and Merck Serono during the conduct of the study. All reported competing interests are outside the submitted work. No other relationships or activities that could appear to have influenced the submitted work. Netherlands trial register, number NTR 1586. 13 January 2009. 20 April 2009. © The Author 2016. Published by Oxford University Press on behalf of the European Society of Human Reproduction and Embryology. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

A randomized controlled, non-inferiority trial of modified natural versus artificial cycle for cryo-thawed embryo transfer

PubMed Central

Groenewoud, E.R.; Cohlen, B.J.; Al-Oraiby, A.; Brinkhuis, E.A.; Broekmans, F.J.M.; de Bruin, J.P.; van den Dool, G.; Fleisher, K.; Friederich, J.; Goddijn, M.; Hoek, A.; Hoozemans, D.A.; Kaaijk, E.M.; Koks, C.A.M.; Laven, J.S.E.; van der Linden, P.J.Q.; Manger, A.P.; Slappendel, E.; Spinder, T.; Kollen, B.J.; Macklon, N.S.

2016-01-01

Abstract STUDY QUESTION Are live birth rates (LBRs) after artificial cycle frozen-thawed embryo transfer (AC-FET) non-inferior to LBRs after modified natural cycle frozen-thawed embryo transfer (mNC-FET)? SUMMARY ANSWER AC-FET is non-inferior to mNC-FET with regard to LBRs, clinical and ongoing pregnancy rates (OPRs) but AC-FET does result in higher cancellation rates. WHAT IS ALREADY KNOWN Pooling prior retrospective studies of AC-FET and mNC-FET results in comparable pregnancy and LBRs. However, these results have not yet been confirmed by a prospective randomized trial. STUDY DESIGN, SIZE AND DURATION In this non-inferiority prospective randomized controlled trial (acronym ‘ANTARCTICA’ trial), conducted from February 2009 to April 2014, 1032 patients were included of which 959 were available for analysis. The primary outcome of the study was live birth. Secondary outcomes were clinical and ongoing pregnancy, cycle cancellation and endometrium thickness. A cost-efficiency analysis was performed. PARTICIPANT/MATERIALS, SETTING, METHODS This study was conducted in both secondary and tertiary fertility centres in the Netherlands. Patients included in this study had to be 18–40 years old, had to have a regular menstruation cycle between 26 and 35 days and frozen-thawed embryos to be transferred had to derive from one of the first three IVF or IVF–ICSI treatment cycles. Patients with a uterine anomaly, a contraindication for one of the prescribed medications in this study or patients undergoing a donor gamete procedure were excluded from participation. Patients were randomized based on a 1:1 allocation to either one cycle of mNC-FET or AC-FET. All embryos were cryopreserved using a slow-freeze technique. MAIN RESULTS AND THE ROLE OF CHANCE LBR after mNC-FET was 11.5% (57/495) versus 8.8% in AC-FET (41/464) resulting in an absolute difference in LBR of −0.027 in favour of mNC-FET (95% confidence interval (CI) −0.065–0.012; P = 0.171). Clinical pregnancy occurred in 94/495 (19.0%) patients in mNC-FET versus 75/464 (16.0%) patients in AC-FET (odds ratio (OR) 0.8, 95% CI 0.6–1.1, P = 0.25). 57/495 (11.5%) mNC-FET resulted in ongoing pregnancy versus 45/464 (9.6%) AC-FET (OR 0.7, 95% CI 0.5–1.1, P = 0.15). χ2 test confirmed the lack of superiority. Significantly more cycles were cancelled in AC-FET (124/464 versus 101/495, OR 1.4, 95% CI 1.1–1.9, P = 0.02). The costs of each of the endometrial preparation methods were comparable (€617.50 per cycle in NC-FET versus €625.73 per cycle in AC-FET, P = 0.54). LIMITATIONS, REASONS FOR CAUTION The minimum of 1150 patients required for adequate statistical power was not achieved. Moreover, LBRs were lower than anticipated in the sample size calculation. WIDER IMPLICATIONS OF THE FINDINGS LBRs after AC-FET were not inferior to those achieved by mNC-FET. No significant differences in clinical and OPR were observed. The costs of both treatment approaches were comparable. STUDY FUNDING/COMPETING INTEREST(S) An educational grant was received during the conduct of this study. Merck Sharpe Dohme had no influence on the design, execution and analyses of this study. E.R.G. received an education grant by Merck Sharpe Dohme (MSD) during the conduct of the present study. B.J.C. reports grants from MSD during the conduct of the study. A.H. reports grants from MSD and Ferring BV the Netherlands and personal fees from MSD. Grants from ZonMW, the Dutch Organization for Health Research and Development. J.S.E.L. reports grants from Ferring, MSD, Organon, Merck Serono and Schering-Plough during the conduct of the study. F.J.M.B. receives monetary compensation as member of the external advisory board for Merck Serono, consultancy work for Gedeon Richter, educational activities for Ferring BV, research cooperation with Ansh Labs and a strategic cooperation with Roche on automated anti Mullerian hormone assay development. N.S.M. reports receiving monetary compensations for external advisory and speaking work for Ferring BV, MSD, Anecova and Merck Serono during the conduct of the study. All reported competing interests are outside the submitted work. No other relationships or activities that could appear to have influenced the submitted work. TRIAL REGISTRATION NUMBER Netherlands trial register, number NTR 1586. TRIAL REGISTRATION DATE 13 January 2009. FIRST PATIENT INCLUDED 20 April 2009. PMID:27179265

AC electrical characterisation and insight to charge transfer mechanisms in DNA molecular wires through temperature and UV effects.

PubMed

Kassegne, Sam; Wibowo, Denni; Chi, James; Ramesh, Varsha; Narenji, Alaleh; Khosla, Ajit; Mokili, John

2015-06-01

In this study, AC characterisation of DNA molecular wires, effects of frequency, temperature and UV irradiation on their conductivity is presented. λ-DNA molecular wires suspended between high aspect-ratio electrodes exhibit highly frequency-dependent conductivity that approaches metal-like behaviour at high frequencies (∼MHz). Detailed temperature dependence experiments were performed that traced the impedance response of λ-DNA until its denaturation. UV irradiation experiments where conductivity was lost at higher and longer UV exposures helped to establish that it is indeed λ-DNA molecular wires that generate conductivity. The subsequent renaturation of λ-DNA resulted in the recovery of current conduction, providing yet another proof of the conducting DNA molecular wire bridge. The temperature results also revealed hysteretic and bi-modal impedance responses that could make DNA a candidate for nanoelectronics components like thermal transistors and switches. Further, these experiments shed light on the charge transfer mechanism in DNA. At higher temperatures, the expected increase in thermal-induced charge hopping may account for the decrease in impedance supporting the 'charge hopping mechanism' theory. UV light, on the other hand, causes damage to GC base-pairs and phosphate groups reducing the path available both for hopping and short-range tunneling mechanisms, and hence increasing impedance--this again supporting both the 'charge hopping' and 'tunneling' mechanism theories.

Structural investigation of vanadium ions doped Li2Osbnd PbOsbnd B2O3sbnd P2O5 glasses by means of spectroscopic and dielectric studies

NASA Astrophysics Data System (ADS)

Yusub, S.; Narendrudu, T.; Suresh, S.; Krishna Rao, D.

2014-11-01

In the present investigation we report the synthesis of a series of transparent glasses of composition 20Li2Osbnd 20PbOsbnd 45B2O3sbnd (15-x) P2O5: xV2O5 with eight values of x ranging from 0 to 2.5 mol%, and their characterization. X-ray diffraction (XRD) spectra reflected the amorphous nature of the glasses. Optical absorption, electron paramagnetic resonance (EPR) spectra and FTIR study of vanadyl ions in the present glass network have been analyzed. The optical absorption and EPR investigations have revealed that vanadium ions do exist in both V4+ and V5+ states and the redox ratio (V4+/V5+) is observed to increase with the increase in concentration of V2O5. Dielectric properties viz., dielectric constant ε‧(ω), loss tan δ, electrical moduli M‧(ω), M″(ω), a.c. conductivity σac over an extensive scale of frequency and temperature have been investigated as a function of V2O5 concentration. The dispersion of dielectric constant ε‧(ω) with temperature has been interpreted by space charge polarization model. The dielectric loss and electrical moduli variation with frequency and temperature exhibited relaxation effects. These effects are ascribed to V4+ ions. The a.c. conductivity of the prepared glasses is perceived to escalate with the hike in V2O5 concentration whereas the activation energy for conduction exhibits a reverse trend. The conductivity mechanism is explained on the basis of polaronic transfer between V4+ and V5+ ions. The low temperature a.c. conductivity mechanism is elucidated by the quantum mechanical tunneling model. The growth in the values of dielectric parameters with raise in the concentration of V2O5 is due to V4+ ions which act as modifiers. The investigation of these results has indicated that at higher concentrations of V2O5, the VO2+ ions in the glasses were present in octahedral sites with tetragonal compression and belong to C4v symmetry.

Dielectric and piezoelectric properties of hydroxyapatite-BaTiO3 composites

NASA Astrophysics Data System (ADS)

Bowen, C. R.; Gittings, J.; Turner, I. G.; Baxter, F.; Chaudhuri, J. B.

2006-09-01

This letter describes the relationships between the composition and the dielectric and piezoelectric properties of hydroxyapatite-barium titanate composites for polarized bone substitutes. The ac conductivity and permittivity were characterized from 0.1Hzto1MHz, along with measurements of the d33 piezoelectric charge coefficient. The addition of BaTiO3 led to an increase in permittivity and ac conductivity of the material. The increase in both properties was attributed to the presence of the high permittivity ferroelectric phase. The d33 and g33 coefficients decreased rapidly as hydroxyapatite was introduced into BaTiO3 material. Composites below 80% by volume of BaTiO3 exhibited no net piezoelectric effect.

Similarity between the superconductivity in the graphene with the spin transport in the two-dimensional antiferromagnet in the honeycomb lattice

NASA Astrophysics Data System (ADS)

Lima, L. S.

2017-02-01

We have used the Dirac's massless quasi-particles together with the Kubo's formula to study the spin transport by electrons in the graphene monolayer. We have calculated the electric conductivity and verified the behavior of the AC and DC currents of this system, that is a relativistic electron plasma. Our results show that the AC conductivity tends to infinity in the limit ω → 0 , similar to the behavior obtained for the spin transport in the two-dimensional frustrated antiferromagnet in the honeycomb lattice. We have made a diagrammatic expansion for the Green's function and we have not gotten significative change in the results.

77 FR 24684 - Proposed Information Collection; Comment Request; 2013-2015 American Community Survey Methods...

Federal Register 2010, 2011, 2012, 2013, 2014

2012-04-25

... program that is designed to address and respond to survey issues and needs. During the 2013-2015 period... Design Test, a 2015 ACS Content Test, and a series of Internet tests. Since the ACS Methods Panel is designed to address emerging issues, we may conduct additional testing as needed. Testing would focus on...

Interplay between the Dzyaloshinskii-Moriya term and external fields on spin transport in the spin-1/2 one-dimensional antiferromagnet

NASA Astrophysics Data System (ADS)

Lima, L. S.

2018-05-01

We study the effect of the uniform Dzyaloshinskii-Moriya interaction (symmetric exchange anisotropy) and arbitrary oriented external magnetic fields on spin conductivity in the spin-1/2 one-dimensional Heisenberg antiferromagnet. The spin conductivity is calculated employing abelian bosonization and the Kubo formalism of transport. We investigate the influence of three competing phases at zero-temperature, (Néel phase, dimerized phase and gapless Luttinger liquid phase) on the AC spin conductivity.

Electrode and grain-boundary effects on the conductivity of CaCu{sub 3}Ti{sub 4}O{sub 12}

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang Lei

2005-07-11

The ac conductivity of CaCu{sub 3}Ti{sub 4}O{sub 12} (CCTO) ceramics was studied in the temperature range 173

Electrical conductivity and morphology of electrochemical synthesized polyaniline/CuO nano composites

NASA Astrophysics Data System (ADS)

Ashokkumar, S. P.; Yesappa, L.; Vijeth, H.; Niranjana, M.; Devendrappa, H.

2018-05-01

Polyaniline (PANI) and Polyaniline/CuO nanocomposite have been synthesized by using electrochemical deposition method. The composite was characterized using Fourier transform infra-red spectroscopy (FT-IR) to confirm the chemical interaction changes, micro structural morphology was done by Field Emission Scanning Electronic Microscopy (FESEM) and High Resolution Transmission Electron Microscopy (HRTEM). The dielectric constant and AC conductivity are found to increases with increase in temperature range (303 to 393K), these results shows enhancement in electrical conductivity due to effect of nanocomposite.

Electrical conduction in PVDF/ZnO-Ag nanocomposites

NASA Astrophysics Data System (ADS)

Singh, Utpal; Jha, Anal K.; Chandra, K. P.; Kolte, Jayant; Kulkarni, A. R.; Prasad, K.

2018-05-01

A hybrid combination of Ag and ZnO nanoparticles were utilized to fabricate PVDF/ZnO(90/10)-Ag nanocomposites (with Ag as filler: 0.5, 1 and 1.5%) utilizing melt-mixing technique. X-ray diffraction study confirmed the formations of nanocomposites. Electric modulus analysis indicated the dielectric relaxation in this system to be of non- Debye type. Correlated barrier hopping model successfully explained the charge conduction in PVDF/ZnO-Ag nanocomposites and ac conductivity data followed Jonscher's power law.

Impedance analysis on PVA/PVP: GO blend nanocomposite polymer films

NASA Astrophysics Data System (ADS)

Rao, M. C.; Basha, S. K. Shahenoor; Kumar, B. Ranjit

2018-05-01

Nanocomposite polymer films have been prepared by doping Graphene oxide (GO) in PVA/PVP blend polymers by solution cast technique. AC conductivity studies were performed on to the prepared nanocomposite films and the maximum ionic conductivity is found to be 6.13x10-4 Scm-1 for (0.30:0.3) wt% of nanocomposite polymer film at room temperature. The maximum ionic conductivity of nanocomposite polymer films of PVA/PVP: GO holds great promise in potential applications.

The barriers associated with emergency medical service use for acute coronary syndrome: the awareness and influence of an Australian public mass media campaign.

PubMed

Cartledge, Susie; Finn, Judith; Straney, Lahn; Ngu, Phillip; Stub, Dion; Patsamanis, Harry; Shaw, James; Bray, Janet

2017-07-01

Emergency medical services (EMS) transport to hospital is recommended in acute coronary syndrome (ACS) guidelines, but only half of patients with ACS currently use EMS. The recent Australian Warning Signs campaign conducted by the Heart Foundation addressed some of the known barriers against using EMS. Our aim was to examine the influence of awareness of the campaign on these barriers in patients with ACS. Interviews were conducted with patients admitted to an Australian tertiary hospital between July 2013 and April 2014 with a diagnosis of ACS. Patient selection criteria included: aged 35-75 years, competent to provide consent, English speaking, not in residential care and medically stable. Multivariable logistic regression was used to examine factors associated with EMS use. Only 54% of the 199 patients with ACS interviewed used EMS for transport to hospital. Overall 64% of patients recalled seeing the campaign advertising, but this was not associated with increased EMS use (52.0%vs56.9%, p=0.49) or in the barriers against using EMS. A large proportion of patients (43%) using other transport thought it would be faster. Factors associated with EMS use for ACS were: age >65 years, ST-elevation myocardial infarction, a sudden onset of pain and experiencing vomiting. In medically stable patients with ACS, awareness of the Australian Warning Signs campaign was not associated with increased use of EMS or a change in the barriers for EMS use. Future education strategies could emphasise the clinical role that EMS provide in ACS. © Article author(s) (or their employer(s) unless otherwise stated in the text of the article) 2017. All rights reserved. No commercial use is permitted unless otherwise expressly granted.

Dielectric Performance of a High Purity HTCC Alumina at High Temperatures - a Comparison Study with Other Polycrystalline Alumina

NASA Technical Reports Server (NTRS)

Chen, Liangyu

2014-01-01

A very high purity (99.99+%) high temperature co-fired ceramic (HTCC) alumina has recently become commercially available. The raw material of this HTCC alumina is very different from conventional HTCC alumina, and more importantly there is no glass additive in this alumina material for co-firing processing. Previously, selected HTCC and LTCC (low temperature co-fired ceramic) alumina materials were evaluated at high temperatures as dielectric and compared to a regularly sintered 96% polycrystalline alumina (96% Al2O3), where 96% alumina was used as the benchmark. A prototype packaging system based on regular 96% alumina with Au thickfilm metallization successfully facilitated long term testing of high temperature silicon carbide (SiC) electronic devices for over 10,000 hours at 500 C. In order to evaluate this new high purity HTCC alumina for possible high temperature packaging applications, the dielectric properties of this HTCC alumina substrate were measured and compared with those of 96% alumina and a previously tested LTCC alumina from room temperature to 550 C at frequencies of 120 Hz, 1 KHz, 10 KHz, 100 KHz, and 1 MHz. A parallel-plate capacitive device with dielectric of the HTCC alumina and precious metal electrodes were used for measurements of the dielectric constant and dielectric loss of the co-fired alumina material in the temperature and frequency ranges. The capacitance and AC parallel conductance of the capacitive device were directly measured by an AC impedance meter, and the dielectric constant and parallel AC conductivity of the dielectric were calculated from the capacitance and conductance measurement results. The temperature and frequency dependent dielectric constant, AC conductivity, and dissipation factor of the HTCC alumina substrate are presented and compared to those of 96% alumina and a selected LTCC alumina. Other technical advantages of this new co-fired material for possible high packaging applications are also discussed.

Anisotropic dyonic black brane and its effects on holographic conductivity

NASA Astrophysics Data System (ADS)

Khimphun, Sunly; Lee, Bum-Hoon; Park, Chanyong; Zhang, Yun-Long

2017-10-01

We investigate a massive gravity theory involving the SL(2 , R) symmetry and anisotropy. Due to the SL(2 , R) invariance of the equations of motion, the complex con-ductivity of this model transforms covariantly under the SL(2 , R) transformation and the ratio of DC conductivities in different spatial directions is preserved even after the SL(2 , R) transformation. We further investigate AC and Hall conductivities by utilizing the Kubo formula. There exists a Drude-like peak in the region with a small anisotropy, while such a Drude peak disappears when anisotropy becomes large. We also show that the complex conductivity can have a cyclotron frequency pole even beyond the hydrodynamic limit.

Polaronic conductivity and scaling behavior of lithium iron phosphate glass

NASA Astrophysics Data System (ADS)

Banday, Azeem; Murugavel, Sevi

2018-05-01

Charge transport properties of the Lithium Iron Phosphate (LFP) glass has been investigated in a wide frequency and temperature range by means of broadband dielectric spectroscopy. The conductivity spectra has been studied on the basis of Jonscher power law for characterizing the hopping dynamics of charge carriers. The ac conductivity and scaling behavior of the LFP glass has been studied in the temperature range from 333K to 573K and frequency range from 100 mHz to 1 MHz. The conductivity isotherms of LFP glass do not superimpose upon each other by using Summerfield scaling. The structural peculiarities in the material could result in different conduction pathways giving rise to the deviation from Summerfield scaling.

Breath Alcohol Concentrations of Designated Drivers

PubMed Central

Barry, Adam E.; Chaney, Beth H.; Stellefson, Michael L.

2013-01-01

Objective: This study established breath alcohol concentrations (BrACs) and alcohol-related behaviors of designated drivers (DDs) to determine (a) whether DDs are abstaining from drinking, (b) whether alcohol-related behaviors of non-DDs and DDs were different, and (c) whether the alcohol consumption of DDs resulted in BrAC levels that affected driving performance or caused psychomotor impairment. Method: We conducted six anonymous field studies during a 3-month period in a southeastern college community restaurant and bar district. Intercept interviews were conducted with 1,071 bar patrons. Alcohol-related behaviors, BrAC, and whether one was serving as a DD were measured. The sample was primarily White (72.7%), male (62.4%) college students (64.7%). Descriptive statistics and an independent sample t test compared the BrACs of DDs versus non-DDs. A one-way analysis of variance examined the differences in the alcohol-related behaviors (Alcohol Use Disorders Identification Test–consumption [AUDIT-C] score) across DDs abstaining from drinking (BrAC = .00 g/210 L), drinking DDs (BrACs ≥ .02 and < .05 g/210 L), and impaired DDs (BrACs ≥ .05 g/210 L). A logistic regression assessed the impact of alcohol-related behaviors (AUDIT-C) on whether one was serving as a DD. Results: Of the 165 DDs, approximately 40% did not abstain from drinking. Approximately 17% of DDs had BrACs between .02 g/210 L and .049 g/210 L, whereas 18% recorded BrACs at .05 g/210 L or greater. The mean AUDIT-C score for impaired DDs significantly differed from both abstaining DDs and drinking DDs. Participants with greater AUDIT-C scores were more likely to serve as a DD and have a BrAC that significantly inhibited driving ability and psychomotor function. Conclusions: These findings identify the need for consensus across researcher, layperson, and communication campaigns that a DD must be someone who has abstained from drinking entirely. PMID:23739013

Development and clinical application of an evidence-based pharmaceutical care service algorithm in acute coronary syndrome.

PubMed

Kang, J E; Yu, J M; Choi, J H; Chung, I-M; Pyun, W B; Kim, S A; Lee, E K; Han, N Y; Yoon, J-H; Oh, J M; Rhie, S J

2018-06-01

Drug therapies are critical for preventing secondary complications in acute coronary syndrome (ACS). The purpose of this study was to develop and apply a pharmaceutical care service (PCS) algorithm for ACS and confirm that it is applicable through a prospective clinical trial. The ACS-PCS algorithm was developed according to extant evidence-based treatment and pharmaceutical care guidelines. Quality assurance was conducted through two methods: literature comparison and expert panel evaluation. The literature comparison was used to compare the content of the algorithm with the referenced guidelines. Expert evaluations were conducted by nine experts for 75 questionnaire items. A trial was conducted to confirm its effectiveness. Seventy-nine patients were assigned to either the pharmacist-included multidisciplinary team care (MTC) group or the usual care (UC) group. The endpoints of the trial were the prescription rate of two important drugs, readmission, emergency room (ER) visit and mortality. The main frame of the algorithm was structured with three tasks: medication reconciliation, medication optimization and transition of care. The contents and context of the algorithm were compliant with class I recommendations and the main service items from the evidence-based guidelines. Opinions from the expert panel were mostly positive. There were significant differences in beta-blocker prescription rates in the overall period (P = .013) and ER visits (four cases, 9.76%, P = .016) in the MTC group compared to the UC group, respectively. We developed a PCS algorithm for ACS based on the contents of evidence-based drug therapy and the core concept of pharmacist services. © 2018 John Wiley & Sons Ltd.

Frequency dependent electrical characteristics of ferroelectric Pb{4.0}K{1.0}Li{1.0}Nb{10}O{30} ceramics

NASA Astrophysics Data System (ADS)

Rao, K. S.; Krishna, P. M.; Prasad, D. M.; Latha, T. S.; Hussain, M.

2007-09-01

Dielectric, impedance, modulus and conductivity studies were performed over temperature 35 °C 600 °C and frequency 45 Hz 5 MHz range on the Lead Potassium Lithium Niobate (Pb{4.0}K{1.0}Li{1.0}Nb{10}O{30}, PKLN) ceramics. These studies established the conduction ion motion and polarization mechanism in the material. The dispersive dielectric loss at high temperature reveals the ionic conductivity. From frequency variation of \\varepsilonl response the pre-factor A(T) and critical exponent n(T) are evaluated, and are used in Jonscher's dielectric dispersion relation for \\varepsilon ' to fit with the experimental data. Complex impedance plots showed a non Debye type relaxation, are used to evaluate the grain and grain boundary conduction and relaxation activation energies. DC and ac conduction activation energies are estimated from Arrhenius plots. Occupancy of Li+ for C-sites gave a completely filled structure and enhanced the phase transition temperature to 520 °C compared to PKN. This is supported by the conduction activation energy in ferro region is more than the para region. Also, the dc conductivity characterized from bulk resistance and M^ll peak frequency. Polaron hoping mechanism at room temperature has been confirmed via the linear variation of the plot log (σ ac-σ dc) as a function of log ω 2. Stretched exponential parameter, β (0 < β ≤slant 1) has been evaluated from impedance plots, interpreted as a result of correlated motions between the Li+ ions and distribution of dielectric relaxation. Compared the results from different techniques, and discussed the conduction mechanism in the material.

Anomalous three-dimensional bulk ac conduction within the Kondo gap of SmB 6 single crystals

DOE Office of Scientific and Technical Information (OSTI.GOV)

Laurita, N. J.; Morris, C. M.; Koohpayeh, S. M.

The Kondo insulator SmB 6 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. Some recent theoretical calculations suggest that SmB 6 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. We investigate themore » low energy optical conductivity within the hybridization gap of single crystals of SmB 6 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 SmB 6 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 SmB 6 is discussed. In addition, 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 .« less

Anomalous three-dimensional bulk ac conduction within the Kondo gap of SmB 6 single crystals

DOE PAGES

Laurita, N. J.; Morris, C. M.; Koohpayeh, S. M.; ...

2016-10-21

The Kondo insulator SmB 6 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. Some recent theoretical calculations suggest that SmB 6 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. We investigate themore » low energy optical conductivity within the hybridization gap of single crystals of SmB 6 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 SmB 6 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 SmB 6 is discussed. In addition, 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 .« less

Studies on frequency dependent electrical and dielectric properties of sintered zinc oxide pellets: effects of Al-doping

NASA Astrophysics Data System (ADS)

Tewari, S.; Ghosh, A.; Bhattacharjee, A.

2016-11-01

Sintered pellets of zinc oxide (ZnO), both undoped and Al-doped are prepared through a chemical process. Dopant concentration of Aluminium in ZnO [Al/Zn in weight percentage (wt%)] is varied from 0 to 3 wt%. After synthesis structural characterisation of the samples are performed with XRD and SEM-EDAX which confirm that all the samples are of ZnO having polycrystalline nature with particle size from 108.6 to 116 nm. Frequency dependent properties like a.c. conductivity, capacitance, impedance and phase angle are measured in the frequency range 10 Hz to 100 kHz as a function of temperature (in the range 25-150 °C). Nature of a.c. conductivity in these samples indicates hopping type of conduction arising from localised defect states. The frequency and temperature dependent properties under study are found to be as per correlated barrier hoping model. Dielectric and impedance properties studied in the samples indicate distributed relaxation, showing decrease of relaxation time with temperature.

Auto-combustion synthesis and characterization of Mg doped CuAlO{sub 2} nanoparticles

DOE Office of Scientific and Technical Information (OSTI.GOV)

Agrawal, Shraddha, E-mail: shraddhaa32@gmail.com; Parveen, Azra; Naqvi, A. H.

2015-06-24

The synthesis of pure and Mg doped Copper aluminumoxide CuAlO{sub 2}nanoparticles, a promising p-type TCO (transparent conducting oxide) have been done bysol gel auto combustion method using NaOH as a fuel, calcinated at 600°C. The structural properties were examined by XRD and SEM techniques. The optical absorption spectra of CuAlO{sub 2} sample recorded by UV-VIS spectrophotometer in the range of 200 to 800 nm have been presented. The crystallite size was determined by powder X-ray diffraction technique. The electrical behavior of pure and Mg doped CuAlO{sub 2} has been studied over a wide range of frequencies by using complex impedance spectroscopy.Themore » variation of a.c. conductivity has been studied as function of frequency and temperature. The data taken together conclude that doping causes decreases in the ac conductivity of the nanoparticles as compared with the pure nanoparticles. Mg doping affects the optical properties and band gap.« less

Auto-combustion synthesis and characterization of Mg doped CuAlO2 nanoparticles

NASA Astrophysics Data System (ADS)

Agrawal, Shraddha; Parveen, Azra; Naqvi, A. H.

2015-06-01

The synthesis of pure and Mg doped Copper aluminumoxide CuAlO2nanoparticles, a promising p-type TCO (transparent conducting oxide) have been done bysol gel auto combustion method using NaOH as a fuel, calcinated at 600°C. The structural properties were examined by XRD and SEM techniques. The optical absorption spectra of CuAlO2 sample recorded by UV-VIS spectrophotometer in the range of 200 to 800 nm have been presented. The crystallite size was determined by powder X-ray diffraction technique. The electrical behavior of pure and Mg doped CuAlO2 has been studied over a wide range of frequencies by using complex impedance spectroscopy.The variation of a.c. conductivity has been studied as function of frequency and temperature. The data taken together conclude that doping causes decreases in the ac conductivity of the nanoparticles as compared with the pure nanoparticles. Mg doping affects the optical properties and band gap.

Highly conductive porous Na-embedded carbon nanowalls for high-performance capacitive deionization

NASA Astrophysics Data System (ADS)

Chang, Liang; Hu, Yun Hang

2018-05-01

Highly conductive porous Na-embedded carbon nanowalls (Na@C), which were recently invented, have exhibited excellent performance for dye-sensitized solar cells and electric double-layer capacitors. In this work, Na@C was demonstrated as an excellent electrode material for capacitive deionization (CDI). In a three-electrode configuration system, the specific capacity of the Na@C electrodes can achieve 306.4 F/g at current density of 0.2 A/g in 1 M NaCl, which is higher than that (235.2 F/g) of activated carbon (AC) electrodes. Furthermore, a high electrosorption capacity of 8.75 mg g-1 in 100 mg/L NaCl was obtained with the Na@C electrodes in a batch-mode capacitive deionization cell. It exceeds the electrosorption capacity (4.08 mg g-1) of AC electrodes. The Na@C electrode also showed a promising cycle stability. The excellent performance of Na@C electrode for capacitive deionization (CDI) can be attributed to its high electrical conductivity and large accessible surface area.

γ-rays irradiation effects on dielectric properties of Ti/Au/GaAsN Schottky diodes with 1.2%N

NASA Astrophysics Data System (ADS)

Teffahi, A.; Hamri, D.; Djeghlouf, A.; Abboun Abid, M.; Saidane, A.; Al Saqri, N.; Felix, J. F.; Henini, M.

2018-06-01

Dielectric properties of As grown and irradiated Ti /Au/GaAsN Schottky diodes with 1.2%N are investigated using capacitance/conductance-voltage measurements in 90-290 K temperature range and 50-2000 kHz frequency range. Extracted parameters are interface state density, series resistance, dielectric constant, dielectric loss, tangent loss and ac conductivity. It is shown that exposure to γ-rays irradiation leads to reduction in effective trap density believed to result from radiation-induced traps annulations. An increase in series resistance is attributed to a net doping reduction. Dielectric constant (ε') shows usual step-like transitions with corresponding relaxation peaks in dielectric loss. These peaks shift towards lower temperature as frequency decrease. Temperature dependant ac conductivity followed an Arrhenius relation with activation energy of 153 meV in the 200-290 K temperature range witch correspond to As vacancy. The results indicate that γ-rays irradiation improves the dielectric and electrical properties of the diode due to the defect annealing effect.

Effect of activated charcoal on callus growth and shoot organogenesis in tobacco. [Nicotiana tabacum

DOE Office of Scientific and Technical Information (OSTI.GOV)

Constantin, M.J.; Henke, R.R.; Mansur, M.A.

1977-01-01

Incorporating activated charcoal (AC) in culture media has been shown to affect growth and development of various organisms. Since AC stimulates the development of tobacco haploid plantlets from cultured anthers, research was conducted to determine the effect of activated charcoal on pith-derived callus growth and shoot development in Nicotiana tabacum cv. Wisconsin 38. Our results indicate that the hormones required for callus growth and shoot development in Wisconsin-38 tobacco are adsorbed by AC, thereby inhibiting callus growth and prohibiting shoot development. This effect was observed even when AC was removed from the medium by filtration prior to culturing the callus.

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.

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.

Sulfurized activated carbon for high energy density supercapacitors

NASA Astrophysics Data System (ADS)

Huang, Yunxia; Candelaria, Stephanie L.; Li, Yanwei; Li, Zhimin; Tian, Jianjun; Zhang, Lili; Cao, Guozhong

2014-04-01

Sulfurized activated carbon (SAC), made by coating the pore surface with thiophenic sulfur functional groups from the pyrolysis of sulfur flakes, were characterized and tested for supercapacitor applications. From X-ray photoelectron spectroscopy (XPS), the sulfur content in the SAC was found to be 2.7 at%. Electrochemical properties from potentiostatic and galvanostatic measurements, and electrochemical impedance spectroscopy (EIS) were used to evaluate the effect of sulfur on porous carbon electrodes. The SAC electrode exhibits better conductivity, and an obvious increase in specific capacitance that is almost 40% higher than plain activated carbons (ACs) electrode at a high current density of 1.4 A g-1. The proposed mechanism for improved conductivity and capacitive performance due to the sulfur functional groups on ACs will be discussed.

Enhanced Dielectric Constant for Efficient Electromagnetic Shielding Based on Carbon-Nanotube-Added Styrene Acrylic Emulsion Based Composite

PubMed Central

2010-01-01

An efficient electromagnetic shielding composite based on multiwalled carbon nanotubes (MWCNTs)-filled styrene acrylic emulsion-based polymer has been prepared in a water-based system. The MWCNTs were demonstrated to have an effect on the dielectric constants, which effectively enhance electromagnetic shielding efficiency (SE) of the composites. A low conductivity threshold of 0.23 wt% can be obtained. An EMI SE of ~28 dB was achieved for 20 wt% MWCNTs. The AC conductivity (σac) of the composites, deduced from imaginary permittivity, was used to estimate the SE of the composites in X band (8.2–12.4 GHz), showing a good agreement with the measured results. PMID:20596498

Waiting for the evidence: VEMP testing and the ability to differentiate utricular versus saccular function.

PubMed

Welgampola, Miriam S; Carey, John P

2010-08-01

The advent of cervical vestibular evoked myogenic potentials (CVEMPs) marked a milestone in clinical vestibular testing because they provided a simple means of assessing human otolith function. The availability of air-conducted (AC) sound and bone-conducted vibration (BCV) to evoke CVEMPs and development of a new technique of recording ocular vestibular-evoked myogenic potentials (OVEMPs) have increased the complexity of this simple test, yet extended its diagnostic capabilities. Here we highlight the evidence-based assumptions that guide interpretation of AC sound- and BCV-evoked VEMPs and the gaps in VEMP research thus far. Copyright (c) 2010 American Academy of Otolaryngology-Head and Neck Surgery Foundation. Published by Mosby, Inc. All rights reserved.

Dynamic Scattering Mode LCDs

NASA Astrophysics Data System (ADS)

Bahadur, Birendra

The following sections are included: * INTRODUCTION * CELL DESIGNING * EXPERIMENTAL OBSERVATIONS IN NEMATICS RELATED WITH DYNAMIC SCATTERING * Experimental Observations at D.C. Field and Electrode Effects * Experimental Observation at Low Frequency A.C. Fields * Homogeneously Aligned Nematic Regime * Williams Domains * Dynamic Scattering * Experimental Observation at High Frequency A.C. Field * Other Experimental Observations * THEORETICAL INTERPRETATIONS * Felici Model * Carr-Helfrich Model * D.C. Excitation * Dubois-Violette, de Gennes and Parodi Model * Low Freqency or Conductive Regime * High Frequency or Dielectric Regime * DYNAMIC SCATTERING IN SMECRIC A PHASE * ELECTRO-OPTICAL CHARACTERISTICS AND LIMITATIONS * Contrast Ratio vs. Voltage, Viewing Angle, Cell Gap, Wavelength and Temperature * Display Current vs. Voltage, Cell Gap and Temperature * Switching Time * Effect of Alignment * Effect of Conductivity, Temperature and Frequency * Addressing of DSM LCDs * Limitations of DSM LCDs * ACKNOWLEDGEMENTS * REFERENCES

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.

Testing of a 1.25-m HTS Cable Made from YBCO Tapes

NASA Astrophysics Data System (ADS)

Gouge, M. J.; Lue, J. W.; Demko, J. A.; Duckworth, R. C.; Fisher, P. W.; Daumling, M.; Lindsay, D. T.; Roden, M. L.; Tolbert, J. C.

2004-06-01

Ultera and Oak Ridge National Laboratory (ORNL) have jointly designed, built, and tested a 1.25-m-long, prototype high-temperature superconducting (HTS) power cable made from 1-cm-wide, second-generation YBa2Cu3Ox (YBCO)-coated conductor tapes. Electrical tests of this cable were performed in boiling liquid nitrogen at 77 K. DC testing of the 1.25-m cable included determination of the V-I curve, with a critical current of 4200 A. This was consistent with the properties of the 24 individual YBCO tapes. AC testing of the cable was conducted at currents up to 2500 Arms. The ac losses were measured calorimetrically by measuring the response of a calibrated temperature sensor placed on the former and electrically by use of a Rogowski coil with a lock-in amplifier. AC losses of about 2 W/m were measured at a cable ac current of 2000 Arms. Overcurrent testing was conducted at peak current values up to 12 kA for pulse lengths of 0.1-0.2 s. The cable temperature increased to 105 K for a 12 kA, 0.2 s overcurrent pulse, and the cable showed no degradation after the sequence of overcurrent testing. This commercial-grade HTS cable demonstrated the feasibility of second-generation YBCO tapes in an ac cable application.

Repeat surveys of spawning cisco (Coregonus artedi) in western Lake Superior: timing, distribution and composition of spawning stocks

USGS Publications Warehouse

Yule, Daniel L.; Schreiner, Donald R.; Addison, Peter A.; Seider, Michael J.; Evrard, Lori M.; Geving, Steven A.; Quinlan, Henry R.

2012-01-01

Acoustic (AC) and midwater trawl (MT) surveys of spawning cisco (Coregonus artedi) in Lake Superior have been combined with commercial yield to estimate exploitation. To time surveys properly, it is important to understand when adults typically arrive at spawning grounds and how numbers change as the spawning season progresses. We conducted repeat autumn surveys during nighttime hours at coastal sites where commercial roe fisheries occur. Spawner densities increased significantly from October to mid-November, but differences measured at sites sampled from mid- to late-November were comparatively small. Spawners occupied the upper 20–30 m of the water column during mid-November before utilizing a wider range of depths by late-November. We compared repeat AC densities to temporal trends of catch-per-unit-effort (CPUE) in suspended commercial gillnets and found good agreement within sites. Because different gillnet mesh sizes were used in each roe fishery. CPUE and AC density were poorly correlated among sites. We recommend that future surveys be conducted between mid- and late-November, and that MT gear be used to measure cisco densities in the uppermost 10 m of the water column where AC estimates may be conservative. Given the short temporal window for assessing spawner density, we believe both AC-MT and gillnet surveys will be needed to ensure that harvest of different stocks is kept at a sustainable level.

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

AC-conductance and capacitance measurements for ethanol vapor detection using carbon nanotube-polyvinyl alcohol composite based devices.

PubMed

Greenshields, Márcia W C C; Meruvia, Michelle S; Hümmelgen, Ivo A; Coville, Neil J; Mhlanga, Sabelo D; Ceragioli, Helder J; Quispe, Jose C Rojas; Baranauskas, Vitor

2011-03-01

We report the preparation of inexpensive ethanol sensor devices using multiwalled carbon nanotube-polyvinyl alcohol composite films deposited onto interdigitated electrodes patterned on phenolite substrates. We investigate the frequency dependent response of the device conductance and capacitance showing that higher sensitivity is obtained at higher frequency if the conductance is used as sensing parameter. In the case of capacitance measurements, higher sensitivity is obtained at low frequency. Ethanol detection at a concentration of 300 ppm in air is demonstrated. More than 80% of the sensor conductance and capacitance variation response occurs in less than 20 s.

The Role of Cervical and Ocular Vestibular Evoked Myogenic Potentials in the Assessment of Patients with Vestibular Schwannomas

PubMed Central

Chiarovano, Elodie; Darlington, Cynthia; Vidal, Pierre-Paul; Lamas, Georges; de Waele, Catherine

2014-01-01

Objectives To investigate the clinical utility of VEMPs in patients suffering from unilateral vestibular schwannoma (VS) and to determine the optimal stimulation parameter (air conducted sound, bone conducted vibration) for evaluating the function of the vestibular nerve. Methods Data were obtained in 63 patients with non-operated VS, and 20 patients operated on VS. Vestibular function was assessed by caloric, cervical and ocular VEMP testing. 37/63 patients with conclusive ACS ocular VEMPs responses were studied separately. Results In the 63 non-operated VS patients, cVEMPs were abnormal in 65.1% of patients in response to AC STB and in 49.2% of patients to AC clicks. In the 37/63 patients with positive responses from the unaffected side, oVEMPs were abnormal in 75.7% of patients with ACS, in 67.6% with AFz and in 56.8% with mastoid BCV stimulation. In 16% of the patients, VEMPs were the only abnormal test (normal caloric and normal hearing). Among the 26 patients who did not show oVEMP responses on either side with ACS, oVEMPs responses could be obtained with AFz (50%) and with mastoid stimulation (89%). Conclusions The VEMP test demonstrated significant clinical value as it yielded the only abnormal test results in some patients suffering from a unilateral vestibular schwannoma. For oVEMPs, we suggest that ACS stimulation should be the initial test. In patients who responded to ACS and who had normal responses, BCV was not required. In patients with abnormal responses on the affected side using ACS, BCV at AFz should be used to confirm abnormal function of the superior vestibular nerve. In patients who exhibited no responses on either side to ACS, BCV was the only approach allowing assessment of the function of the superior vestibular nerve. We favor using AFz stimulation first because it is easier to perform in clinical practice than mastoid stimulation. PMID:25137289

Electrical conductivity of Gd doped BiFeO3-PbZrO3 composite

NASA Astrophysics Data System (ADS)

Satpathy, Santosh Kumar; Mohanty, Nilaya Kumar; Behera, Ajay Kumar; Behera, Banarji; Nayak, Pratibindhya

2013-09-01

The composite, 0.5(BiGd0.15Fe0.85O3)-0.5(PbZrO3), was synthesized using the solid-state reaction technique. The formation of the compound was confirmed by XRD with an orthorhombic structure at room temperature. The impedance parameters were studied using an impedance analyzer in a wide range of frequency (102-106 Hz) at different temperatures. The Nyquist plot suggests the contribution of bulk effect and a slight indication of grain boundary effect and the bulk resistance decreases with a rise in temperature. The presence of temperature-dependent relaxation process occurs in the material. Electrical modulus reveals the presence of the hopping mechanism in the materials. The value of exponent n, pre-factor A and σ dc were obtained by fitting ac conductivity data with Jonscher's universal power law. The activation energies calculated from the ac conductivity were found to be 0.50, 0.46, 0.44, 0.43, 0.42 and 0.38 eV at 1, 10, 50, 100, 500 kHz and 1 MHz respectively in the temperature region of 110°C-350°C. The dc conductivity was found to increase with the rise in temperature. The activation energy calculated from complex impedance plot and from the fitted Jonscher's power law are very close, which results similar type of charge carrier exist in conduction mechanism of the material.

Graphene-coated coupling coil for AC resistance reduction

DOEpatents

Miller, John M

2014-03-04

At least one graphene layer is formed to laterally surround a tube so that the basal plane of each graphene layer is tangential to the local surface of the tube on which the graphene layer is formed. An electrically conductive path is provided around the tube for providing high conductivity electrical path provided by the basal plane of each graphene layer. The high conductivity path can be employed for high frequency applications such as coupling coils for wireless power transmission to overcome skin depth effects and proximity effects prevalent in high frequency alternating current paths.

Environmental Science and Research Foundation. Annual technical report, April 11, 1994--December 31, 1994

DOE Office of Scientific and Technical Information (OSTI.GOV)

Reynolds, T.D.; Morris, R.C.; Markham, O.D.

1995-06-01

This Annual Technical Report describes work conducted for the Department of Energy, Idaho Operations Office, by the Environmental Science and Research Foundation (Foundation) for work under contract DE-AC07-94ID13268. The Foundation began, on April 11, 1994, to conduct environmental surveillance near to and distant from the Idaho National Engineering Laboratory, provide environmental public relations and education related to INEL natural resource issues, and conduct ecological and radioecological research benefiting major DOE-ID programs including Waste Management, Environmental Restoration, Spent Nuclear Fuels, and Infrastructure.

Effect of nanochitosan and succinonitrile on the AC ionic conductivity of plasticized nanocomposite solid polymer electrolytes (PNCSPE)

NASA Astrophysics Data System (ADS)

Karuppasamy, K.; Vani, C. Vijil; Nichelson, A.; Balakumar, S.; Shajan, X. Sahaya

2013-06-01

In the present study, the filler chitosan was converted into nanochitosan by ionotropic gelation method. Plasticized nanocomposite solid polymer electrolytes (PNCSPE) composed of poly ethylene oxide as host polymer, LiBOB (lithium bis(oxalatoborate)) as salt, SN as plasticizer and nanochitosan as filler were prepared by membrane hot-press technique. Succinonitrile and nanochitosan incorporation in PEO-LiBOB matrix enhanced the room temperature ionic conductivity. The highest ionic conductivities were found to be in the order of 10-3.2 S/cm.

Evaluation of DC electric field distribution of PPLP specimen based on the measurement of electrical conductivity in LN2

NASA Astrophysics Data System (ADS)

Hwang, Jae-Sang; Seong, Jae-Kyu; Shin, Woo-Ju; Lee, Jong-Geon; Cho, Jeon-Wook; Ryoo, Hee-Suk; Lee, Bang-Wook

2013-11-01

High temperature superconducting (HTS) cable has been paid much attention due to its high efficiency and high current transportation capability, and it is also regarded as eco-friendly power cable for the next generation. Especially for DC HTS cable, it has more sustainable and stable properties compared to AC HTS cable due to the absence of AC loss in DC HTS cable. Recently, DC HTS cable has been investigated competitively all over the world, and one of the key components of DC HTS cable to be developed is a cable joint box considering HVDC environment. In order to achieve the optimum insulation design of the joint box, analysis of DC electric field distribution of the joint box is a fundamental process to develop DC HTS cable. Generally, AC electric field distribution depends on relative permittivity of dielectric materials but in case of DC, electrical conductivity of dielectric material is a dominant factor which determines electric field distribution. In this study, in order to evaluate DC electric field characteristics of the joint box for DC HTS cable, polypropylene laminated paper (PPLP) specimen has been prepared and its DC electric field distribution was analyzed based on the measurement of electrical conductivity of PPLP in liquid nitrogen (LN2). Electrical conductivity of PPLP in LN2 has not been reported yet but it should be measured for DC electric field analysis. The experimental works for measuring electrical conductivity of PPLP in LN2 were presented in this paper. Based on the experimental works, DC electric field distribution of PPLP specimen was fully analyzed considering the steady state and the transient state of DC. Consequently, it was possible to determine the electric field distribution characteristics considering different DC applying stages including DC switching on, DC switching off and polarity reversal conditions.

Hot electrons injection in carbon nanotubes under the influence of quasi-static ac-field

NASA Astrophysics Data System (ADS)

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

2016-07-01

The theory of hot electrons injection in carbon nanotubes (CNTs) where both dc electric field (Ez), and a quasi-static ac field exist simultaneously (i.e. when the frequency ω of ac field is much less than the scattering frequency v (ω ⪡ v or ωτ ⪡ 1, v =τ-1) where τ is relaxation time) is studied. The investigation is done theoretically by solving semi-classical Boltzmann transport equation with and without the presence of the hot electrons source to derive the current densities. Plots of the normalized current density versus dc field (Ez) applied along the axis of the CNTs in the presence and absence of hot electrons reveal ohmic conductivity initially and finally negative differential conductivity (NDC) provided ωτ ⪡ 1 (i.e. quasi- static case). With strong enough axial injection of the hot electrons, there is a switch from NDC to positive differential conductivity (PDC) about Ez ≥ 75 kV / cm and Ez ≥ 140 kV / cm for a zigzag CNT and an armchair CNT respectively. Thus, the most important tough problem for NDC region which is the space charge instabilities can be suppressed due to the switch from the NDC behaviour to the PDC behaviour predicting a potential generation of terahertz radiations whose applications are relevance in current-day technology, industry, and research.

Abdominal compartment syndrome and ruptured aortic aneurysm: Validation of a predictive test (SCA-AAR).

PubMed

Leclerc, Betty; Salomon Du Mont, Lucie; Parmentier, Anne-Laure; Besch, Guillaume; Rinckenbach, Simon

2018-06-01

The abdominal compartment syndrome (ACS) has been clearly identified as being one of the main causes of mortality after ruptured abdominal aortic aneurysm (rAAA). The ACS is defined as a sustained intra-abdominal pressure > 20 mm Hg associated with a new organ dysfunction or failure. A pilot study was conducted and found that the threshold of 3 among 8 selected criteria, we would predict an ACS occurrence with a 54% positive predictive value and a 92% negative predictive value. But a multicentric prospective study was clearly needed to confirm these results. The outcome of this new study is to assess the qualities of a predictive test on occurrence of the ACS after rAAA surgery. This is a 30 months prospective cohort study conducted in 12 centers and 165 patients will be included. All patients with a rAAA will be consecutively included, whatever the surgical treatment. At the end of surgery, all patients have an abdominal closure and a monitoring of intrabladder pressure will be established every 3 to 4 hours. Decompressive laparotomy will be indicated when ACS occurs. Follow-up period is 1 month. Eight pre- and per-operative criteria will be studied: anemia, hypotension, cardiac arrest, obesity, massive fluid resuscitation, transfusion, hypothermia, and acidosis. In the literature, there is no recommendation about prophylactic decompression, but early decompressive laparotomy appears to improve survival. This study should make it possible to establish a predictive test, detect the ACS early, and consider a prophylactic decompression in the operating room. ClinicalTrials.gov, NCT02859662, Registered on 4 August 2016.

Electromigration analysis of solder joints under ac load: A mean time to failure model

NASA Astrophysics Data System (ADS)

Yao, Wei; Basaran, Cemal

2012-03-01

In this study, alternating current (ac) electromigration (EM) degradation simulations were carried out for Sn95.5%Ag4.0%Cu0.5 (SAC405- by weight) solder joints. Mass transport analysis was conducted with viscoplastic material properties for quantifying damage mechanism in solder joints. Square, sine, and triangle current wave forms ac were used as input signals. dc and pulsed dc (PDC) electromigration analysis were conducted for comparison purposes. The maximum current density ranged from 2.2×106A/cm2 to 5.0×106A/cm2, frequency ranged from 0.05 Hz to 5 Hz with ambient temperature varying from 350 K to 450 K. Because the room temperature is nearly two-thirds of SAC solder joint's melting point on absolute temperature scale (494.15 K), viscoplastic material model is essential. Entropy based damage evolution model was used to investigate mean time to failure (MTF) behavior of solder joints subjected to ac stressing. It was observed that MTF was inversely proportional to ambient temperature T1.1 in Celsius and also inversely proportional to current density j0.27 in A/cm2. Higher frequency will lead to a shorter lifetime with in the frequency range we studied, and a relationship is proposed as MTF∝f-0.41. Lifetime of a solder joint subjected to ac is longer compared with dc and PDC loading conditions. By introducing frequency, ambient temperature and current density dependency terms, a modified MTTF equation was proposed for solder joints subjected to ac current stressing.

Frequency- and doping-level influence on electric and dielectric properties of PolySi/SiO2/cSi (MOS) structures

NASA Astrophysics Data System (ADS)

Doukhane, N.; Birouk, B.

2018-03-01

The electric and dielectric characteristics of PolySi/SiO2/cSi (MOS) structure, such as series resistance ( R s), dielectric constants ( ɛ') and ( ɛ″), dielectric losses (tan δ), and the ac electric conductivity ( σ ac), were studied in the frequency range 100 kHz-1 MHz for various doping levels and two thicknesses for the polysilicon layer (100 and 175 nm). The experimental results show that the C and G/ ω characteristics are very sensitive to the frequency due to the presence of interface states. Series resistance R s is deduced from C and G/ ω measurements and is plotted as a function of the frequency for various doping levels. It is found to decrease with frequency and doping level. To determine {ɛ ^' }, ɛ″, tan δ, and {σ _{{ac}}}, the admittance technique was used. An interesting behavior of the constants, {ɛ ^' } and ɛ″, was noticed. The {ɛ ^' } values fit led to relations between {ɛ ^' } and the frequency, on one hand, and between {ɛ ^' } and the electric conductivity of the polysilicon layers on the other. These relations make it possible to interpolate directly between two experimental points for a given frequency. The analysis of the results shows that the values of {ɛ ^' }, ɛ″, and tan δ decrease with increasing frequency. This is due to the fact that in the region of low frequencies, interfacial polarization occurs easily, and the interface states between Si and SiO2 contribute to the improvement of the dielectric properties of the PolySi/SiO2/cSi structures. The study also emphasizes that the ac electric conductivity increases with the increase in frequency and doping level; this causes to the reduction in series resistance.

Audiometric analyses confirm a cochlear component, disproportional to age, in stapedial otosclerosis.

PubMed

Topsakal, Vedat; Fransen, Erik; Schmerber, Sébastien; Declau, Frank; Yung, Matthew; Gordts, Frans; Van Camp, Guy; Van de Heyning, Paul

2006-09-01

To report the preoperative audiometric profile of surgically confirmed otosclerosis. Retrospective, multicenter study. Four tertiary referral centers. One thousand sixty-four surgically confirmed patients with otosclerosis. Therapeutic ear surgery for hearing improvement. Preoperative audiometric air conduction (AC) and bone conduction (BC) hearing thresholds were obtained retrospectively for 1064 patients with otosclerosis. A cross-sectional multiple linear regression analysis was performed on audiometric data of affected ears. Influences of age and sex were analyzed and age-related typical audiograms were created. Bone conduction thresholds were corrected for Carhart effect and presbyacusis; in addition, we tested to see if separate cochlear otosclerosis component existed. Corrected thresholds were than analyzed separately for progression of cochlear otosclerosis. The study population consisted of 35% men and 65% women (mean age, 44 yr). The mean pure-tone average at 0.5, 1, and 2 kHz was 57 dB hearing level. Multiple linear regression analysis showed significant progression for all measured AC and BC thresholds. The average annual threshold deterioration for AC was 0.45 dB/yr and the annual threshold deterioration for BC was 0.37 dB/yr. The average annual gap expansion was 0.08 dB/year. The corrected BC thresholds for Carhart effect and presbyacusis remained significantly different from zero, but only showed progression at 2 kHz. The preoperative audiological profile of otosclerosis is described. There is a significant sensorineural component in patients with otosclerosis planned for stapedotomy, which is worse than age-related hearing loss by itself. Deterioration rates of AC and BC thresholds have been reported, which can be helpful in clinical practice and might also guide the characterization of allegedly different phenotypes for familial and sporadic otosclerosis.

In situ conductance measurements of copper phthalocyanine thin film growth on sapphire [0001].

PubMed

Murdey, Richard; Sato, Naoki

2011-06-21

The current flowing through a thin film of copper phthalocyanine vacuum deposited on a single crystal sapphire [0001] surface was measured during film growth from 0 to 93 nm. The results, expressed as conductance vs. nominal film thickness, indicate three distinct film growth regions. Conductive material forms below about 5 nm and again above 35 nm, but in the intermediate thicknesses the film conductance was observed to decrease with increasing film thickness. With the aid of ac-AFM topology images taken ex situ, the conductance results are explained based on the Stranski-Krastanov (2D + 3D) film growth mechanism, in which the formation of a thin wetting layer is followed by the growth of discrete islands that eventually coalesce into an interpenetrating, conductive network. © 2011 American Institute of Physics

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.

The vestibular evoked myogenic potential (VEMP): air- versus bone-conducted stimuli.

PubMed

McNerney, Kathleen M; Burkard, Robert F

2011-01-01

Several studies have evaluated the effects of different stimulus and recording parameters on the cervical vestibular evoked myogenic potential (cVEMP); however, it is difficult to directly compare these studies as they have all used different recording methods, different sternocleidomastoid (SCM) muscle contraction/electromyography monitoring methods, and different stimulus parameters. : This study made a direct comparison of the cVEMP in response to air-conducted (AC) and bone-conducted (BC) stimuli in the same subjects, using the same stimulus/recording/electromyography monitoring methods. We found that the input/output (I/O) functions were more linear in response to AC stimuli, whereas cVEMPs in response to BC stimuli began to saturate at the highest level. In addition, cVEMP threshold was obtained at a lower stimulus level (i.e., at a lower sensation level) in response to BC stimuli as compared with AC stimuli, and cVEMPs in response to BC stimuli were larger than cVEMPs in response to AC stimuli, which is in agreement with what has been found in previous studies. In addition, this was one of the few studies to evaluate the repeatability of the cVEMP in response to BC stimuli. Interestingly, we found that cVEMP latency in response to BC stimuli was, in most cases, less variable than cVEMP latency obtained in response to AC stimuli, whereas the reverse was true for cVEMP amplitude. We also found that BC masking presented to the forehead affected response amplitude of the AC cVEMP regardless of the specific SCM muscle contraction/toneburst presentation condition. In addition, we found that the ratio of amplitude reduction was greater in the binaural stimulation/bilateral SCM muscle contraction condition as compared with the monaural stimulation/bilateral SCM muscle contraction condition. The present experiment provided a direct comparison of the cVEMP in response to AC versus BC 500 Hz short-duration toneburst stimuli in the same subjects. The results of the present experiment also provide insight into the laterality of the cVEMP response and reveal that the cVEMP may not be completely ipsilateral (i.e., there may be a form of bilateral interaction that occurs when both sides are stimulated simultaneously). Last, the results indicate that BC stimuli likely activates the saccule as well as the utricle, given that AC VEMPs can be masked by the administration of BC masking noise presented to the midline.

Lack of genotoxicity in vivo for food color additive Allura Red AC.

PubMed

Bastaki, Maria; Farrell, Thomas; Bhusari, Sachin; Pant, Kamala; Kulkarni, Rohan

2017-07-01

Allura Red AC is an approved food color additive internationally with INS number 129, in the United States as food color subject to batch certification "Food, Drug, and Cosmetic" (FD&C) Red No. 40, and in Europe as food color additive with E number 129. In their evaluation of the color (2013), the European Food Safety Authority (EFSA) expressed concerns of potential genotoxicity, based primarily on one genotoxicity study that was not conducted according to Guidelines. The present in vivo genotoxicity study was conducted according to OECD Guidelines in response to EFSA's request for additional data. The animal species and strain, and the tissues examined were selected specifically to address the previously reported findings. The results show clear absence of genotoxic activity for Allura Red AC, in the bone marrow micronucleus assay and the Comet assay in the liver, stomach, and colon. These data addressed EFSA's concerns for genotoxicity. The Joint WHO/FAO Committee on Food Additives (JECFA) (2016) also reviewed the study and concluded that there is no genotoxicity concern for Allura Red AC. Negative findings in parallel genotoxicity studies on Tartrazine and Ponceau 4R (published separately) are consistent with lack of genotoxicity for azo dyes used as food colors. Copyright © 2017 Elsevier Ltd. All rights reserved.

Central and peripheral hemodynamics in exercising humans: leg vs arm exercise.

PubMed

Calbet, J A L; González-Alonso, J; Helge, J W; Søndergaard, H; Munch-Andersen, T; Saltin, B; Boushel, R

2015-12-01

In humans, arm exercise is known to elicit larger increases in arterial blood pressure (BP) than leg exercise. However, the precise regulation of regional vascular conductances (VC) for the distribution of cardiac output with exercise intensity remains unknown. Hemodynamic responses were assessed during incremental upright arm cranking (AC) and leg pedalling (LP) to exhaustion (Wmax) in nine males. Systemic VC, peak cardiac output (Qpeak) (indocyanine green) and stroke volume (SV) were 18%, 23%, and 20% lower during AC than LP. The mean BP, the rate-pressure product and the associated myocardial oxygen demand were 22%, 12%, and 14% higher, respectively, during maximal AC than LP. Trunk VC was reduced to similar values at Wmax. At Wmax, muscle mass-normalized VC and fractional O2 extraction were lower in the arm than the leg muscles. However, this was compensated for during AC by raising perfusion pressure to increase O2 delivery, allowing a similar peak VO2 per kg of muscle mass in both extremities. In summary, despite a lower Qpeak during arm cranking the cardiovascular strain is much higher than during leg pedalling. The adjustments of regional conductances during incremental exercise to exhaustion depend mostly on the relative intensity of exercise and are limb-specific. © 2015 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

History of the U.S. Navy Body Composition program.

PubMed

Peterson, David D

2015-01-01

The Navy currently employs maximum weight-for-height tables and body fat prediction equations based on circumference measurements to assess body composition. However, many Sailors believe the current method fails to accurately predict body fat percentage. As a result, the Naval Health Research Center (NHRC) conducted numerous studies in an attempt to improve the accuracy and reliability of the Navy's Body Composition Analysis program. In 2012, NHRC conducted a study that researched the feasibility of using a single abdominal circumference (AC) measurement in lieu of circumference measurements. The Air Force and National Institutes of Health (NIH) employ a single AC measurement taken at the superior border of the iliac crest to assess body composition and all-cause mortality risk. Although the Air Force and NIH use the iliac crest, NHRC is proposing the Navy use the umbilicus as the AC site since it is less invasive and easier to identify. If implemented, the Navy would use cutoff values of 40 in. and 36 in. for males and females, respectively. The purpose of this article is to provide a brief history of the Navy's Body Composition Analysis program as well as propose the transition from circumference measurements to a single AC measurement. Reprint & Copyright © 2015 Association of Military Surgeons of the U.S.

An Objective Estimation of Air-Bone-Gap in Cochlear Implant Recipients with Residual Hearing Using Electrocochleography.

PubMed

Koka, Kanthaiah; Saoji, Aniket A; Attias, Joseph; Litvak, Leonid M

2017-01-01

Although, cochlear implants (CI) traditionally have been used to treat individuals with bilateral profound sensorineural hearing loss, a recent trend is to implant individuals with residual low-frequency hearing. Notably, many of these individuals demonstrate an air-bone gap (ABG) in low-frequency, pure-tone thresholds following implantation. An ABG is the difference between audiometric thresholds measured using air conduction (AC) and bone conduction (BC) stimulation. Although, behavioral AC thresholds are straightforward to assess, BC thresholds can be difficult to measure in individuals with severe-to-profound hearing loss because of vibrotactile responses to high-level, low-frequency stimulation and the potential contribution of hearing in the contralateral ear. Because of these technical barriers to measuring behavioral BC thresholds in implanted patients with residual hearing, it would be helpful to have an objective method for determining ABG. This study evaluated an innovative technique for measuring electrocochleographic (ECochG) responses using the cochlear microphonic (CM) response to assess AC and BC thresholds in implanted patients with residual hearing. Results showed high correlations between CM thresholds and behavioral audiograms for AC and BC conditions, thereby demonstrating the feasibility of using ECochG as an objective tool for quantifying ABG in CI recipients.

Theory of the dynamical thermal conductivity of metals

NASA Astrophysics Data System (ADS)

Bhalla, Pankaj; Kumar, Pradeep; Das, Nabyendu; Singh, Navinder

2016-09-01

The Mori's projection method, known as the memory function method, is an important theoretical formalism to study various transport coefficients. In the present work, we calculate the dynamical thermal conductivity in the case of metals using the memory function formalism. We introduce thermal memory functions for the first time and discuss the behavior of thermal conductivity in both the zero frequency limit and in the case of nonzero frequencies. We compare our results for the zero frequency case with the results obtained by the Bloch-Boltzmann kinetic approach and find that both approaches agree with each other. Motivated by some recent experimental advancements, we obtain several new results for the ac or the dynamical thermal conductivity.

Meissner mechanism for the spin supercurrent and interplay between quantum phase transition and spin transport in the frustrated Heisenberg model

NASA Astrophysics Data System (ADS)

Lima, Leonardo S.

2018-04-01

We have propose the Meissner mechanism for the spin supercurrent in quantum spin systems. Besides, we study the behavior of the AC spin conductivity in neighborhood of quantum phase transition in a frustrated spin model such as the antiferromagnet in the union jack lattice with single ion anisotropy at T = 0 . We investigate the spin conductivity for this model that presents exchange interactions J1 and J2 . Our results show a single peak for the conductivity with the height varying with the behavior of critical anisotropy Dc with J2 . We obtain the conductivity tending to zero in the limit ω → 0 .

Effect of cochlear implantation on middle ear function: A three-month prospective study.

PubMed

Wasson, Joseph D; Campbell, Luke; Chambers, Scott; Hampson, Amy; Briggs, Robert J S; O'Leary, Stephen J

2018-05-01

To determine if cochlear implantation has a delayed effect on the middle ear conductive hearing mechanism by measuring laser Doppler vibrometry (LDV) of the tympanic membrane (TM) in both implanted and contralateral control ears preoperatively and 3 months postoperatively, and then comparing the relative change in LDV outcome measures between implanted and control ears. Prospective cohort study. Eleven preoperative adult unilateral cochlear implant recipients in previously unoperated ears with normal anatomy and aerated temporal bones were included in this study. The magnitude and phase angle of umbo velocity transfer function in response to air- conduction (AC) stimulus, and the magnitude of umbo velocity in response to bone- conduction (BC) stimulus were measured in the implant ear and the contralateral control ear preoperatively and 3 months postoperatively and compared. No significant changes in the magnitude or phase angle of TM velocity in response to either AC or BC stimulus were observed in the implanted ear relative to the contralateral control ear 3 months following cochlear implantation. From the results of LDV measurements, it can be said that cochlear implantation has no significant delayed effect on the middle ear conductive mechanism. 4. Laryngoscope, 128:1207-1212, 2018. © 2017 The American Laryngological, Rhinological and Otological Society, Inc.

Dielectric and conductivity studies of Co-Cu mixed ferrite

NASA Astrophysics Data System (ADS)

Parveez, Asiya; Shekhawat, M. S.; Nayeem, Firdous; Mohd. Shariff, S.; Sinha, R. R.; Khader, S. Abdul

2018-05-01

Nanoparticles of Co-Cu mixed ferrite having the basic composition Co1-xCuxFe2O4(x=0, 0.2, 0.4, 0.6, 0.8 and 1.0) were synthesized using nitrate-citrate combustion method. Structural, dielectric and a.c conductivity of nanopowders, which are sintered at 900°C were studied. Powder X-ray diffraction studies confirmed phase and their nanocrystalline nature. The peaks observed in the XRD spectrum indicated single phase spinel cubic structure for the synthesized samples. Surface morphology of the samples has been investigated using High ResolutionScanning Electron Microscope. The dielectric constant (ɛ') and dielectric loss factor (ɛ″) of nanocrystalline Co-Cu mixed ferrites were investigated as a function of frequency and Cu+2 concentration at room temperature over the frequency range 100 Hz to 1 MHz using Hioki make LCR Hi-Tester 3250. Synthesized mixed ferrites exhibited usual dielectric dispersion, dependence of ɛ' and ɛ″ with the frequency of the alternating applied electric field is in accordance with the Maxwell-Wagner type interfacial polarization. The electrical conductivity (σac) deduced from the measured dielectric data has been thoroughly analyzed and found that the conduction mechanism in Co1-xCuxFe2O4 mixed nanoferrites are in conformity with the electron hopping model.

Electrolysis of simulated lunar melts

NASA Technical Reports Server (NTRS)

Lewis, R. H.; Lindstrom, D. J.; Haskin, L. A.

1985-01-01

Electrolysis of molten lunar soil or rock is examined as an attractive means of wresting useful raw materials from lunar rocks. It requires only hat to melt the soil or rock and electricity to electrolyze it, and both can be developed from solar power. The conductivities of the simple silicate diopside, Mg CaSi2O6 were measured. Iron oxide was added to determine the effect on conductivity. The iron brought about substantial electronic conduction. The conductivities of simulated lunar lavas were measured. The simulated basalt had an AC conductivity nearly a fctor of two higher than that of diopside, reflecting the basalt's slightly higher total concentration of the 2+ ions Ca, Mg, and Fe that are the dominant charge carriers. Electrolysis was shown to be about 30% efficient for the basalt composition.

Effects of hydrogenation on thermal conductivity of ultrananocrystalline diamond/amorphous carbon composite films prepared via coaxial arc plasma deposition

NASA Astrophysics Data System (ADS)

Takeichi, Satoshi; Nishiyama, Takashi; Tabara, Mitsuru; Kawawaki, Shuichi; Kohno, Masamichi; Takahashi, Koji; Yoshitake, Tsuyoshi

2018-06-01

Ultrananocrystalline diamond (UNCD)/hydrogenated amorphous carbon (a-C:H) composite (UNCD/a-C:H) and UNCD/non-hydrogenated amorphous carbon (a-C) composite (UNCD/a-C) films were prepared via coaxial arc plasma deposition, and their thermal conductivity and interfacial conductance in grain boundaries were measured using a time-domain thermoreflectance method. The interfacial conductance was estimated to be 1,010 and 4,892 MW/(m2·K) for UNCD/a-C:H and UNCD/a-C films, respectively. The reasons for the hydrogenated film having lower interfacial conductance than the non-hydrogenated film are 1) the reduced number of carriers that contribute to heat transport and 2) the hydrogen atoms, which are preferentially located at the grain boundaries and enhance phonon scattering.

The mechanism of detection of air pollution by an ionization chamber.

PubMed

Novković, D; Vukanac; Milosević, Z

2000-01-01

The mechanism of detection of chemical vapors in air by an ionization chamber supplied by DC and AC voltage has been described. The theoretical explanation is based on numerical solutions of the differential equations of the cylindrical ionization chamber. The current of the ionization chamber operating in the AC regime has two components: a conductive component, caused by the ions drifts, and a capacitive component, caused by the distortion of the electric field. The ionization chamber operating in the DC regime has only the first component; hence the AC supplied chamber has larger response than the DC supplied chamber.

Detection of γ-radiation and heavy metals using electrochemical bacterial-based sensor

NASA Astrophysics Data System (ADS)

Al-Shanawa, M.; Nabok, A.; Hashim, A.; Smith, T.; Forder, S.

2013-06-01

The main aim of this work is to develop a simple electrochemical sensor for detection of γ-radiation and heavy metals using bacteria. A series of DC and AC electrical measurements were carried out on samples of two types of bacteria, namely Escherichia coli and Deinococcus radiodurans. As a first step, a correlation between DC and AC electrical conductivity and bacteria concentration in solution was established. The study of the effect of γ-radiation and heavy metal ions (Cd2+) on DC and AC electrical characteristics of bacteria revealed a possibility of pattern recognition of the above inhibition factors.

Electron Transport in Multi-Terminal Graphene Nanodevice with Inclined Cross Structures

NASA Astrophysics Data System (ADS)

Ye, En-Jia; Shi, Yi-Jian; Zhao, Xuean

2014-12-01

The DC and AC transport properties are investigated in multi-terminal graphene nanoribbon (GNR) devices. The devices are composed of three or four graphene ribbons connected with different angles. It is found that DC and AC conductances depend on the structural configurations and ribbon properties. In the vicinity of Dirac point, the intersection of graphene ribbons forms band mixing and results in resonant or anti-resonant states. The edge and width, as well as, the angles of the graphene ribbons influence the DC and AC transport properties drastically. These properties can be used to build future graphene-based nanoelectronics.

Optical devices having flakes suspended in a host fluid to provide a flake/fluid system providing flakes with angularly dependent optical properties in response to an alternating current electric field due to the dielectric properties of the system

DOEpatents

Kosc, Tanya Z [Rochester, NY; Marshall, Kenneth L [Rochester, NY; Jacobs, Stephen D [Pittsford, NY

2006-05-09

Optical devices utilizing flakes (also called platelets) suspended in a host fluid have optical characteristics, such as reflective properties, which are angular dependent in response to an AC field. The reflectivity may be Bragg-like, and the characteristics are obtained through the use of flakes of liquid crystal material, such as polymer liquid crystal (PLC) materials including polymer cholesteric liquid crystal (PCLC) and polymer nematic liquid crystal (PNLC) material or birefringent polymers (BP). The host fluid may be propylene carbonate, poly(ethylene glycol) or other fluids or fluid mixtures having fluid conductivity to support conductivity in the flake/host system. AC field dependent rotation of 90.degree. can be obtained at rates and field intensities dependent upon the frequency and magnitude of the AC field. The devices are useful in providing displays, polarizers, filters, spatial light modulators and wherever switchable polarizing, reflecting, and transmission properties are desired.

Temperature and composition dependent density of states extracted using overlapping large polaron tunnelling model in MnxCo1-xFe2O4 (x=0.25, 0.5, 0.75) nanoparticles

NASA Astrophysics Data System (ADS)

Jamil, Arifa; Afsar, M. F.; Sher, F.; Rafiq, M. A.

2017-03-01

We report detailed ac electrical and structural characterization of manganese cobalt ferrite nanoparticles, prepared by coprecipitation technique. X-ray diffraction (XRD) confirmed single-phase cubic spinel structure of the nanoparticles. Tetrahedral (A) and octahedral (B) group complexes were present in the spinel lattice as determined by Fourier Transform Infrared Spectroscopy (FTIR). Scanning Electron Microscope (SEM) images revealed presence of spherical shape nanoparticles having an average diameter 50-80 nm. Composition, temperature and frequency dependent ac electrical study of prepared nanoparticles interpreted the role of cationic distribution between A and B sites. Overlapping large polaron tunnelling (OLPT) conduction mechanism was observed from 290 to 200 K. Frequency exponent s was fitted theoretically using OLPT model. High values of Density of States (DOS) of the order of 1022-1024 eV-1 cm-3 were extracted from ac conductivity for different compositions. We found that DOS was dependent on distribution of cations in the tunnel-type cavities along the a and b axis.

Oxygen surface exchange kinetics measurement by simultaneous optical transmission relaxation and impedance spectroscopy: Sr(Ti,Fe)O3-x thin film case study.

PubMed

Perry, Nicola H; Kim, Jae Jin; Tuller, Harry L

2018-01-01

We compare approaches to measure oxygen surface exchange kinetics, by simultaneous optical transmission relaxation (OTR) and AC-impedance spectroscopy (AC-IS), on the same mixed conducting SrTi 0.65 Fe 0.35 O 3-x film. Surface exchange coefficients were evaluated as a function of oxygen activity in the film, controlled by gas partial pressure and/or DC bias applied across the ionically conducting yttria-stabilized zirconia substrate. Changes in measured light transmission through the film over time (relaxations) resulted from optical absorption changes in the film corresponding to changes in its oxygen and oxidized Fe (~Fe 4+ ) concentrations; such relaxation profiles were successfully described by the equation for surface exchange-limited kinetics appropriate for the film geometry. The k chem values obtained by OTR were significantly lower than the AC-IS derived k chem values and k q values multiplied by the thermodynamic factor (bulk or thin film), suggesting a possible enhancement in k by the metal current collectors (Pt, Au). Long-term degradation in k chem and k q values obtained by AC-IS was also attributed to deterioration of the porous Pt current collector, while no significant degradation was observed in the optically derived k chem values. The results suggest that, while the current collector might influence measurements by AC-IS, the OTR method offers a continuous, in situ , and contact-free method to measure oxygen exchange kinetics at the native surfaces of thin films.

N-Doped Dual Carbon-Confined 3D Architecture rGO/Fe3O4/AC Nanocomposite for High-Performance Lithium-Ion Batteries.

PubMed

Ding, Ranran; Zhang, Jie; Qi, Jie; Li, Zhenhua; Wang, Chengyang; Chen, Mingming

2018-04-25

To address the issues of low electrical conductivity, sluggish lithiation kinetics and dramatic volume variation in Fe 3 O 4 anodes of lithium ion battery, herein, a double carbon-confined three-dimensional (3D) nanocomposite architecture was synthesized by an electrostatically assisted self-assembly strategy. In the constructed architecture, the ultrafine Fe 3 O 4 subunits (∼10 nm) self-organize to form nanospheres (NSs) that are fully coated by amorphous carbon (AC), formatting core-shell structural Fe 3 O 4 /AC NSs. By further encapsulation by reduced graphene oxide (rGO) layers, a constructed 3D architecture was built as dual carbon-confined rGO/Fe 3 O 4 /AC. Such structure restrains the adverse reaction of the electrolyte, improves the electronic conductivity and buffers the mechanical stress of the entire electrode, thus performing excellent long-term cycling stability (99.4% capacity retention after 465 cycles relevant to the second cycle at 5 A g -1 ). Kinetic analysis reveals that a dual lithium storage mechanism including a diffusion reaction mechanism and a surface capacitive behavior mechanism coexists in the composites. Consequently, the resulting rGO/Fe 3 O 4 /AC nanocomposite delivers a high reversible capacity (835.8 mA h g -1 for 300 cycles at 1 A g -1 ), as well as remarkable rate capability (436.7 mA h g -1 at 10 A g -1 ).

Oxygen surface exchange kinetics measurement by simultaneous optical transmission relaxation and impedance spectroscopy: Sr(Ti,Fe)O3-x thin film case study

PubMed Central

Perry, Nicola H.; Kim, Jae Jin; Tuller, Harry L.

2018-01-01

Abstract We compare approaches to measure oxygen surface exchange kinetics, by simultaneous optical transmission relaxation (OTR) and AC-impedance spectroscopy (AC-IS), on the same mixed conducting SrTi0.65Fe0.35O3-x film. Surface exchange coefficients were evaluated as a function of oxygen activity in the film, controlled by gas partial pressure and/or DC bias applied across the ionically conducting yttria-stabilized zirconia substrate. Changes in measured light transmission through the film over time (relaxations) resulted from optical absorption changes in the film corresponding to changes in its oxygen and oxidized Fe (~Fe4+) concentrations; such relaxation profiles were successfully described by the equation for surface exchange-limited kinetics appropriate for the film geometry. The kchem values obtained by OTR were significantly lower than the AC-IS derived kchem values and kq values multiplied by the thermodynamic factor (bulk or thin film), suggesting a possible enhancement in k by the metal current collectors (Pt, Au). Long-term degradation in kchem and kq values obtained by AC-IS was also attributed to deterioration of the porous Pt current collector, while no significant degradation was observed in the optically derived kchem values. The results suggest that, while the current collector might influence measurements by AC-IS, the OTR method offers a continuous, in situ, and contact-free method to measure oxygen exchange kinetics at the native surfaces of thin films. PMID:29511391

Electrical conductivity, thermopower and 57Fe Mössbauer spectroscopy of aegirine (NaFeSi2O6)

NASA Astrophysics Data System (ADS)

Schmidbauer, E.; Kunzmann, Th.

DC and AC electrical conductivities were measured on samples of two different crystals of the mineral aegirine (NaFeSi2O6) parallel (∥) and perpendicular (⊥) to the [001] direction of the clinopyroxene structure between 200 and 600 K. Impedance spectroscopy was applied (20 Hz-1 MHz) and the bulk DC conductivity σDC was determined by extrapolating AC data to zero frequency. In both directions, the log σDC - 1/T curves bend slightly. In the high- and low-temperature limits, differential activation energies were derived for measurements ∥ [001] of EA 0.45 and 0.35 eV, respectively, and the numbers ⊥ [001] are very similar. The value of σDC ∥ [001] with σDC(300 K) 2.0 × 10-6 Ω-1cm-1 is by a factor of 2-10 above that measured ⊥ [001], depending on temperature, which means anisotropic charge transport. Below 350 K, the AC conductivity σ'(ω) (ω/2π=frequency) is enhanced relative to σDC for both directions with an increasing difference for rising frequencies on lowering the temperature. An approximate power law for σ'(ω) is noted at higher frequencies and low temperatures with σ'(ω) ωs, which is frequently observed on amorphous and disordered semiconductors. Scaling of σ'(ω) data is possible with reference to σDC, which results in a quasi-universal curve for different temperatures. An attempt was made to discuss DC and AC results in the light of theoretical models of hopping charge transport and of a possible Fe2+ --> Fe3+ electron hopping mechanism. The thermopower Θ (Seebeck effect) in the temperature range 360 K < T < 770 K is negative in both directions. There is a linear Θ - 1/T relationship above 400 K with activation energy EΘ 0.030 eV ∥ [001] and 0.070 eV ⊥ [001]. 57Fe Mössbauer spectroscopy was applied to detect Fe2+ in addition to the dominating concentration of Fe3+.

Studies on the thermal and electrical properties of polyethylene oxide/polyvinyl alcohol blend by incorporating of Cesium Chloride

NASA Astrophysics Data System (ADS)

Ragab, H. M.

The composites PVA/PEO filled with various concentrations of CsCl samples, which were prepared for using a solvent casting technique and studied via Fourier transform infrared spectroscopy (FTIR), ultraviolet - visible (UV-Vis), X-ray spectroscopy, Scanning electron microscopy (SEM), AC conductivity and dielectric properties to use as sensor in electronic devices. The FTIR indicated the interaction between PVA/PEO and CsCl. From data of UV. Vis. was observed band gap (Eg) reduces with addition CsCl to polymer blend. The XRD shows the degree of crystallinity (χ%) decreasing with increasing concentration of CsCl from 2.93 to 2.45. The SEM of the surface of composite PVA/PEO filled with various concentrations of CsCl in magnification 1500 times its change with compare of pure blend. From TGA was observed improvement in the thermal stability of the samples after addition of CsCl. The AC conductivity rise more rapidly with temperature and associated with activation energy Ea, for conduction and enhanced with increasing both temperature and frequency.

Structural and electrical properties of nickel substituted cadmium ferrite

NASA Astrophysics Data System (ADS)

Chethan, B.; Raj Prakash, H. G.; Vijayakumari, S. C.; Ravikiran, Y. T.

2018-05-01

Spinal nano-sized Cadmium ferrite (CD) and Nickel substituted cadmium ferrite (NSCF) were fabricated by sol-gel auto combustion method. The formation of spinal structure of ferrite materials was confirmed by X-ray diffraction (XRD) analysis. The crystallites size of CF and NSCF as determined by Scherrer's formula were found to be 24.73 nm and 17.70 nm respectively. comparative study of Fourier transform infrared spectroscopy (FTIR) of CF and NSCF revealed tetrahedral absorption bands shifted slightly towards higher frequency where as octahedral bands shifted towards lower frequency side confirming interfacial interaction between Ni and CF. The AC conductivity (σ), loss tangent (tan δ) and complex plane impedance plots for both CF and NSCF are determined at various frequencies ranging from 50 kHz to 5 MHz and comparatively analyzed. The increase in AC conductivity of the NSCF nano particles as compared to CF was explained in the light of hopping model. The impedance measurement of NSCF show presence of a semi-circle corresponding to the grain boundary resistance and hence shows that the conductivity takes place largely through grain boundaries.

Synthesis and properties of a clean and sustainable deicing additive for asphalt mixture.

PubMed

Peng, Chao; Yu, Jianying; Zhao, Zhijie; Dai, Jing; Fu, Jingyi; Zhao, Meiling; Wang, Wei

2015-01-01

A clean and sustainable deicing additive was prepared via the adsorption of acetate anions (Ac-) by magnesium (Mg) and aluminum (Al) calcined layered double hydroxide (Mg/Al-CLDH). Fourier transform infrared spectroscopy spectrums proved that Ac- had intercalated into LDH structure. X-ray diffraction patterns, scanning electron microscopy and transmission electron microscopy images showed that the intercalation spacing and platelet thickness of Mg and Al layered double hydroxide containing Ac- anions (Mg/Al-Ac- LDH) had been enlarged due to substitution of divalent CO32- anions by a larger quantity of monovalent Ac- anions. Differential scanning calorimetry tests testified that the insoluble Mg2/Al-Ac- LDH evidently decreased the freeze point (FP) of water to -10.68°C. X-ray photoelectron spectroscopy analyses confirmed that the Ac- were strongly confined by the metal layers of LDHs. FP test of asphalt mixtures confirmed that Mg/Al-Ac- LDHs reduced FP to -5.5°C. Immersion test results indicated that Mg/Al-Ac- LDH had a good deicing durability and Ac- did not released from asphalt mixture. Snow melting observation was conducted further testified that Mg/Al-Ac- LDH melted snow or ice sustainably.

The effect of activation agent on surface morphology, density and porosity of palm shell and coconut shell activated carbon

NASA Astrophysics Data System (ADS)

Leman, A. M.; Zakaria, S.; Salleh, M. N. M.; Sunar, N. M.; Feriyanto, D.; Nazri, A. A.

2017-09-01

Activated carbon (AC) has one of the promising alternative technology for filtration and adsorption process. It inexpensive material because the sources is abundant especially in Malaysia. Main purpose of this project is to develop AC by chemical activation process to improve adsorption capacity by improving porosity of AC. AC developed via carbonization using designed burner at temperature of 650°C to 850 °C and activated by Potassium Hydroxide (KOH) in 12 hour and then dried at temperature of 300°C. Characterization and analysis is conducted by Scanning Electron Microscopy (SEM) for surface morphology analysis, Energy Dispersive Spectroscopy (EDS) for composition analysis, density and porosity analysis. Results shows that uneven surface has been observed both of AC and non-AC and also AC shows higher porosity as compared to non-AC materials. Density value of raw material has lower than AC up to 11.67% and 47.54% and porosity of raw material has higher than AC up to 31.45% and 45.69% for palm shell and coconut shell AC. It can be concluded that lower density represent higher porosity of material and higher porosity indicated higher adsorption capacity as well.

Electromagnetic augmentation for casting of thin metal sheets

DOEpatents

Hull, John R.

1989-01-01

Thin metal sheets are cast by magnetically levitating molten metal deposited in a mold within a ferromagnetic yoke and between AC conducting coils and linearly displacing the magnetically levitated liquid metal while it is being cooled by the water-cooled walls of the mold to form a solid metal sheet. A conducting shield is electrically coupled to the molten metal sheet to provide a return path for eddy currents induced in the metal sheet by the current in the AC conducting coils. In another embodiment, a DC conducting coil is coupled to the metal sheet for providing a direct current therein which interacts with the magnetic field to levitate the moving metal sheet. Levitation of the metal sheet in both molten and solid forms reduces its contact pressure with the mold walls while maintaining sufficient engagement therebetween to permit efficient conductive cooling by the mold through which a coolant fluid may be circulated. The magnetic fields associated with the currents in the aforementioned coils levitate the molten metal sheet while the mold provides for its lateral and vertical confinement. A leader sheet having electromagnetic characteristics similar to those of the molten metal sheet is used to start the casing process and precedes the molten metal sheet through the yoke/coil arrangement and mold and forms a continuous sheet therewith. The yoke/coil arrangement may be either U-shaped with a single racetrack coil or may be rectangular with a pair of spaced, facing bedstead coils.

Ionic Conductivity and Potential Application for Fuel Cell of a Modified Imine-Based Covalent Organic Framework.

PubMed

Montoro, Carmen; Rodríguez-San-Miguel, David; Polo, Eduardo; Escudero-Cid, Ricardo; Ruiz-González, Maria Luisa; Navarro, Jorge A R; Ocón, Pilar; Zamora, Félix

2017-07-26

We present the novel potential application of imine-based covalent organic frameworks (COFs), formed by the direct Schiff reaction between 1,3,5-tris(4-aminophenyl)benzene and 1,3,5-benzenetricarbaldehyde building blocks in m-cresol or acetic acid, named RT-COF-1 or RT-COF-1Ac/RT-COF-1AcB. The post-synthetic treatment of RT-COF-1 with LiCl leads to the formation of LiCl@RT-COF-1. The ionic conductivity of this series of polyimine COFs has been characterized at variable temperature and humidity, using electrochemical impedance spectroscopy. LiCl@RT-COF-1 exhibits a conductivity value of 6.45 × 10 -3 S cm -1 (at 313 K and 100% relative humidity) which is among the highest values so far reported in proton conduction for COFs. The mechanism of conduction has been determined using 1 H and 7 Li solid-state nuclear magnetic resonance spectroscopy. Interestingly, these materials, in the presence of controlled amounts of acetic acid and under pressure, show a remarkable processability that gives rise to quasi-transparent and flexible films showing in-plane structural order as confirmed by X-ray crystallography. Finally, we prove that these films are useful for the construction of proton exchange membrane fuel cells (PEMFC) reaching values up to 12.95 mW cm -2 and 53.1 mA cm -2 for maximum power and current density at 323 K, respectively.

Induction voidmeter

DOEpatents

Anderson, Thomas T.; Roop, Conard J.; Schmidt, Kenneth J.; Brewer, John

1986-01-01

An induction voidmeter for detecting voids in a conductive fluid may comprise: a four arm bridge circuit having two adjustable circuit elements connected as opposite arms of said bridge circuit, an input branch, and an output branch; two induction coils, bifilarly wound together, connected as the remaining two opposing arms of said bridge circuit and positioned such that the conductive fluid passes through said coils; applying an AC excitation signal to said input branch; and detecting the output signal generated in response to said excitation signal across said output branch. The induction coils may be located outside or inside a non-magnetic pipe containing the conductive fluid.

Integration of a Miniaturized Conductivity Sensor into an Animal-Borne Instrument

DTIC Science & Technology

2015-09-30

an Animal -Borne Instrument Lars Boehme Sea Mammal Research Unit Scottish Oceans Institute University of St Andrews St Andrews, KY16 8LB United... Kingdom phone: +44 1334-462677 fax: +44 1334-463443 email: lb284@st-andrews.ac.uk Robin Pascal Sensors Development Group National...Oceanography Centre Southampton, SO14 3ZY United Kingdom phone: +44 2380-596138 fax: +44 2380-593029 email: rwp@nerc.ac.uk Phil Lovell

The Use of AC-DC-AC Methods in Assessing Corrosion Resistance Performance of Coating Systems for Magnesium Alloys

NASA Astrophysics Data System (ADS)

McCune, Robert C.; Upadhyay, Vinod; Wang, Yar-Ming; Battocchi, Dante

The potential utility of AC-DC-AC electrochemical methods in comparative measures of corrosion-resisting coating system performance for magnesium alloys under consideration for the USAMP "Magnesium Front End Research and Development" project was previously shown in this forum [1]. Additional studies of this approach using statistically-designed experiments have been conducted with focus on alloy types, pretreatment, topcoat material and topcoat thickness as the variables. Additionally, sample coupons made for these designed experiments were also subjected to a typical automotive cyclic corrosion test cycle (SAE J2334) as well as ASTM B117 for comparison of relative performance. Results of these studies are presented along with advantages and limitations of the proposed methodology.

Magnetic field tunable ac electrical transport of LaFeO3-wax nanocomposites

NASA Astrophysics Data System (ADS)

Roy, Supratim; Mandal, S. K.; Debnath, Rajesh; Nath, Debajyoti; Dey, P.

2018-04-01

Single phase perovskite LaFeO3 nanoparticles have been prepared through chemical pyrophoric reaction process. It is further grinded with paraffin wax of quantity 0.5 wt% of total composition to obtain an organic composite 99.5%LaFeO3-0.5%Wax. Studies of ac electrical properties viz. complex impedance, dielectric response, loss coefficient have been done in presence of external dc magnetic field, which reveals a good magnetoimpedance (˜221%) and a negative magnetodielectric (˜ 64%). The value of impedance, its real and imaginary part is observed to increase with dc field. The composite exhibits high dielectric constant (˜4760). The ac conductivity is found to decrease with applied field and increase with ac frequency.

Enhanced dielectric properties of Fe-substituted TiO2 nanoparticles

NASA Astrophysics Data System (ADS)

Ali, T.; Ahmed, Ateeq; Naseem siddique, M.; Tripathi, P.

2018-04-01

We report the structural and dielectric properties Ti1-xFexO2 (0.00 < x < 0.10) nanoparticles (NPs) synthesized by sol-gel method. The synthesized material has been characterized by soft X-ray absorption spectroscopy (SXAS) in order to investigate the fine structure and electronic valence state. SXAS analysis reveals that Fe-ions exist only in 3+ valance state in all the samples. The dielectric properties were studied by the use of LCR impedance spectroscopy. The dielectric constants, dielectric loss and A.C. conductivity have been determined as a function of frequency and composition of iron. At higher frequencies, the materials exhibited high AC Conductivity and low dielectric constant. The above theory could be explained by 'Maxwell Wagner Model' and may provide a new insight to fabricate nanomaterials having possible electrical application.

Investigation on discharge characteristics of a coaxial dielectric barrier discharge reactor driven by AC and ns power sources

NASA Astrophysics Data System (ADS)

Qian, WANG; Feng, LIU; Chuanrun, MIAO; Bing, YAN; Zhi, FANG

2018-03-01

A coaxial dielectric barrier discharge (DBD) reactor with double layer dielectric barriers has been developed for exhaust gas treatment and excited either by AC power or nanosecond (ns) pulse to generate atmospheric pressure plasma. The comparative study on the discharge characteristics of the discharge uniformity, power deposition, energy efficiency, and operation temperature between AC and ns pulsed coaxial DBD is carried out in terms of optical and electrical characteristics and operation temperature for optimizing the coaxial DBD reactor performance. The voltages across the air gap and dielectric layer and the conduction and displacement currents are extracted from the applied voltages and measured currents of AC and ns pulsed coaxial DBDs for the calculation of the power depositions and energy efficiencies through an equivalent electrical model. The discharge uniformity and operating temperature of the coaxial DBD reactor are monitored and analyzed by optical images and infrared camera. A heat conduction model is used to calculate the temperature of the internal quartz tube. It is found that the ns pulsed coaxial DBD has a much higher instantaneous power deposition in plasma, a lower total power consumption, and a higher energy efficiency compared with that excited by AC power and is more homogeneous and stable. The temperature of the outside wall of the AC and ns pulse excited coaxial DBD reaches 158 °C and 64.3 °C after 900 s operation, respectively. The experimental results on the comparison of the discharge characteristics of coaxial DBDs excited by different powers are significant for understanding of the mechanism of DBDs, reducing energy loss, and optimizing the performance of coaxial DBD in industrial applications.

Frequency and voltage dependent profile of dielectric properties, electric modulus and ac electrical conductivity in the PrBaCoO nanofiber capacitors

NASA Astrophysics Data System (ADS)

Demirezen, S.; Kaya, A.; Yerişkin, S. A.; Balbaşı, M.; Uslu, İ.

In this study, praseodymium barium cobalt oxide nanofiber interfacial layer was sandwiched between Au and n-Si. Frequency and voltage dependence of ε‧, ε‧, tanδ, electric modulus (M‧ and M″) and σac of PrBaCoO nanofiber capacitor have been investigated by using impedance spectroscopy method. The obtained experimental results show that the values of ε‧, ε‧, tanδ, M‧, M″ and σac of the PrBaCoO nanofiber capacitor are strongly dependent on frequency of applied bias voltage. The values of ε‧, ε″ and tanδ show a steep decrease with increasing frequency for each forward bias voltage, whereas the values of σac and the electric modulus increase with increasing frequency. The high dispersion in ε‧ and ε″ values at low frequencies may be attributed to the Maxwell-Wagner and space charge polarization. The high values of ε‧ may be due to the interfacial effects within the material, PrBaCoO nanofibers interfacial layer and electron effect. The values of M‧ and M″ reach a maximum constant value corresponding to M∞ ≈ 1/ε∞ due to the relaxation process at high frequencies, but both the values of M‧ and M″ approach almost to zero at low frequencies. The changes in the dielectric and electrical properties with frequency can be also attributed to the existence of Nss and Rs of the capacitors. As a result, the change in the ε‧, ε″, tanδ, M‧, M″ and ac electric conductivity (σac) is a result of restructuring and reordering of charges at the PrBaCoO/n-Si interface under an external electric field or voltage and interface polarization.

Examining the Link Between Public Transit Use and Active Commuting

PubMed Central

Bopp, Melissa; Gayah, Vikash V.; Campbell, Matthew E.

2015-01-01

Background: An established relationship exists between public transportation (PT) use and physical activity. However, there is limited literature that examines the link between PT use and active commuting (AC) behavior. This study examines this link to determine if PT users commute more by active modes. Methods: A volunteer, convenience sample of adults (n = 748) completed an online survey about AC/PT patterns, demographic, psychosocial, community and environmental factors. t-test compared differences between PT riders and non-PT riders. Binary logistic regression analyses examined the effect of multiple factors on AC and a full logistic regression model was conducted to examine AC. Results: Non-PT riders (n = 596) reported less AC than PT riders. There were several significant relationships with AC for demographic, interpersonal, worksite, community and environmental factors when considering PT use. The logistic multivariate analysis for included age, number of children and perceived distance to work as negative predictors and PT use, feelings of bad weather and lack of on-street bike lanes as a barrier to AC, perceived behavioral control and spouse AC were positive predictors. Conclusions: This study revealed the complex relationship between AC and PT use. Further research should investigate how AC and public transit use are related. PMID:25898405

Synthesis and Properties of a Clean and Sustainable Deicing Additive for Asphalt Mixture

PubMed Central

Peng, Chao; Yu, Jianying; Zhao, Zhijie; Dai, Jing; Fu, Jingyi; Zhao, Meiling; Wang, Wei

2015-01-01

A clean and sustainable deicing additive was prepared via the adsorption of acetate anions (Ac-) by magnesium (Mg) and aluminum (Al) calcined layered double hydroxide (Mg/Al-CLDH). Fourier transform infrared spectroscopy spectrums proved that Ac- had intercalated into LDH structure. X-ray diffraction patterns, scanning electron microscopy and transmission electron microscopy images showed that the intercalation spacing and platelet thickness of Mg and Al layered double hydroxide containing Ac- anions (Mg/Al-Ac- LDH) had been enlarged due to substitution of divalent CO3 2- anions by a larger quantity of monovalent Ac– anions. Differential scanning calorimetry tests testified that the insoluble Mg2/Al-Ac- LDH evidently decreased the freeze point (FP) of water to -10.68°C. X-ray photoelectron spectroscopy analyses confirmed that the Ac- were strongly confined by the metal layers of LDHs. FP test of asphalt mixtures confirmed that Mg/Al-Ac- LDHs reduced FP to -5.5°C. Immersion test results indicated that Mg/Al-Ac- LDH had a good deicing durability and Ac- did not released from asphalt mixture. Snow melting observation was conducted further testified that Mg/Al-Ac- LDH melted snow or ice sustainably. PMID:25625279

Examining the link between public transit use and active commuting.

PubMed

Bopp, Melissa; Gayah, Vikash V; Campbell, Matthew E

2015-04-17

An established relationship exists between public transportation (PT) use and physical activity. However, there is limited literature that examines the link between PT use and active commuting (AC) behavior. This study examines this link to determine if PT users commute more by active modes. A volunteer, convenience sample of adults (n = 748) completed an online survey about AC/PT patterns, demographic, psychosocial, community and environmental factors. t-test compared differences between PT riders and non-PT riders. Binary logistic regression analyses examined the effect of multiple factors on AC and a full logistic regression model was conducted to examine AC. Non-PT riders (n = 596) reported less AC than PT riders. There were several significant relationships with AC for demographic, interpersonal, worksite, community and environmental factors when considering PT use. The logistic multivariate analysis for included age, number of children and perceived distance to work as negative predictors and PT use, feelings of bad weather and lack of on-street bike lanes as a barrier to AC, perceived behavioral control and spouse AC were positive predictors. This study revealed the complex relationship between AC and PT use. Further research should investigate how AC and public transit use are related.

Airway complications have a greater impact on the outcomes of living-donor lobar lung transplantation recipients than cadaveric lung transplantation recipients.

PubMed

Sugimoto, Seiichiro; Yamane, Masaomi; Otani, Shinji; Kurosaki, Takeshi; Okahara, Shuji; Hikasa, Yukiko; Toyooka, Shinichi; Kobayashi, Motomu; Oto, Takahiro

2018-04-21

Airway complications (ACs) after living-donor lobar lung transplantation (LDLLT) could have different features from those after cadaveric lung transplantation (CLT). We conducted this study to compare the characteristics of ACs after LDLLT vs. those after CLT and investigate their impact on outcomes. We reviewed, retrospectively, data on 163 recipients of lung transplantation, including 83 recipients of LDLLT and 80 recipients of CLT. The incidence of ACs did not differ between LDLLT and CLT. The initial type of AC after LDLLT was limited to stenosis in all eight patients, whereas that after CLT consisted of stenosis in three patients and necrosis in ten patients (p = 0.0034). ACs after LDLLT necessitated significantly earlier initiation of treatment than those after CLT (p = 0.032). The overall survival rate of LDLLT recipients with an AC was significantly lower than that of those without an AC (p = 0.030), whereas the overall survival rate was comparable between CLT recipients with and those without ACs (p = 0.25). ACs after LDLLT, limited to bronchial stenosis, require significantly earlier treatment and have a greater adverse impact on survival than ACs after CLT.

Electrical conduction mechanism and dielectric characterization of MnTPPCl thin films

NASA Astrophysics Data System (ADS)

Meikhail, M. S.; Oraby, A. H.; El-Nahass, M. M.; Zeyada, H. M.; Al-Muntaser, A. A.

2018-06-01

The AC conductivity and dielectric properties of MnTPPCl sandwich structure as Au/MnTPPCl/Au were studied. The conductivity of the MnTPPCl thin films have been interpreted by the correlated barrier hopping (CBH) model. The dominant conduction process have found to be the single polaron hopping conduction. The values of the hopping distance, Rω, barrier height, W, and the localized-state density, N, are estimated at different frequencies. The behavior of dielectric constant and dielectric loss was discussed as a function of temperature and frequency. The dielectric constant was described in terms of polarization mechanism in materials. The spectral behavior of dielectric loss is interpreted on the basis of the Giuntini et al. model [1]. The value of WM is obtained as 0.32 eV. A non-Debye relaxation phenomenon was observed from the dielectric relaxation mechanism.

Reconstruction of radial thermal conductivity depth profile in case hardened steel rods

NASA Astrophysics Data System (ADS)

Celorrio, Ricardo; Mendioroz, Arantza; Apiñaniz, Estibaliz; Salazar, Agustín; Wang, Chinhua; Mandelis, Andreas

2009-04-01

In this work the surface thermal-wave field (ac temperature) of a solid cylinder illuminated by a modulated light beam is calculated first in two cases: a multilayered cylinder and a cylinder the radial thermal conductivity of which varies continuously. It is demonstrated numerically that, using a few layers of different thicknesses, the surface thermal-wave field of a cylindrical sample with continuously varying radial thermal conductivity can be calculated with high accuracy. Next, an inverse procedure based on the multilayered model is used to reconstruct the radial thermal conductivity profile of hardened C1018 steel rods, the surface temperature of which was measured by photothermal radiometry. The reconstructed thermal conductivity depth profile has a similar shape to those found for flat samples of this material and shows a qualitative anticorrelation with the hardness depth profile.

Preparation of Some Novel Copper(I) Complexes and their Molar Conductances in Organic Solvents

NASA Astrophysics Data System (ADS)

Gill, Dip Singh; Rana, Dilbag

2009-04-01

Attempts have been made to prepare some novel copper(I) nitrate, sulfate, and perchlorate complexes. Molar conductances of these complexes have been measured in organic solvents like acetonitrile (AN), acetone (AC), methanol (MeOH), N,N-dimethylformamide (DMF), N,Ndimethylacetamide (DMA), and dimethylsulfoxide (DMSO) at 298 K. The molar conductance data have been analyzed to obtain limiting molar conductances (λ0) and ion association constants (KA) of the electrolytes. The results showed that all these complexes are strong electrolytes in all organic solvents. The limiting ionic molar conductances (λo± ) for various ions have been calculated using Bu4NBPh4 as reference electrolyte. The actual radii for copper(I) complex ions are very large and different in different solvents and indicate some solvation effects in each solvent system

Scaling of terahertz conductivity at the metal-insulator transition in doped manganites

NASA Astrophysics Data System (ADS)

Pimenov, A.; Biberacher, M.; Ivannikov, D.; Loidl, A.; Mukhin, A. A.; Goncharov, Yu. G.; Balbashov, A. M.

2006-06-01

Magnetic field and temperature dependence of the terahertz conductivity and permittivity of the colossal magnetoresistance manganite Pr0.65Ca0.28Sr0.07MnO3 (PCSMO) is investigated approaching the metal-to-insulator transition (MIT) from the insulating side. In the charge-ordered state of PCSMO both conductivity and dielectric permittivity increase as a function of magnetic field and temperature. Universal scaling relationships Δɛ∝Δσ are observed in a broad range of temperatures and magnetic fields. Similar scaling is also seen in La1-xSrxMnO3 for different doping levels. The observed proportionality points towards the importance of pure ac-conductivity and phononic energy scale at MIT in manganites.

Novel proton conducting polymer electrolytes based on polyparabanic acid doped with H 3PO 4 for high temperature fuel cell

NASA Astrophysics Data System (ADS)

Aihara, Yuichi; Sonai, Atsuo

Three novel proton conducting polymer electrolytes based on polyparabanic acid doped with H 3PO 4 were synthesized and their use in high temperature fuel cells characterized. The precursor polymers, PMD-Im, POD-Im and PDMDP-Im, were synthesized by cyclization polymerization of diisocynanates. After doping with H 3PO 4, the ionic conductivity and the thermal degradation were studied by using the AC impedance method and thermal gravimetric analysis, respectively. These membranes showed high ionic conductivity of the order of 10 -2 S cm -1 at 423 K with good thermal stability. Their application to fuel cells was demonstrated and polarization curves were obtained at 423 K were obtained without humidification.

Activated carbon with excellent chromium(VI) adsorption performance prepared by acid-base surface modification.

PubMed

Liu, S X; Chen, X; Chen, X Y; Liu, Z F; Wang, H L

2007-03-06

In the present work, activated carbon (AC) with excellent Cr(VI) adsorption performance especially at low concentrations was prepared by an acid-base surface modification method. Raw activated carbon (AC(0)) was first oxidized in boiling HNO(3) (AC(1)), then treated with a mixture of NaOH and NaCl (AC(2)). Batch equilibrium and continuous column adsorption were conducted to evaluate the adsorption performance. Boehm titration, elemental analysis, and N(2)/77K adsorption isotherm methods were used to characterize the surface properties and pore structure of modified ACs. The results revealed that the modified AC exhibited excellent Cr(VI) adsorption performance in terms of adsorption capacity and adsorption rate: AC(2)>AC(1)>AC(0). Modification caused S(BET) to decrease and the total number of surface oxygen acidic groups to increase. HNO(3) oxidization produced positive acid groups, and subsequently NaOH treatment replaced H(+) of surface acid groups by Na(+), and the acidity of AC decreased. The main cause of higher Cr(VI) adsorption capacity and rate for AC(2) was the presence of more oxygen surface acidic groups and suitable surface acidity. HNO(3)-NaOH modification shows potential for the preparation of high quality AC for the effective removal of low concentrations of Cr(VI).

Surface Movement Guidance and Control System

DOT National Transportation Integrated Search

1996-12-12

This Advisory Circular (AC) describes the standards and provides guidance in the : development of a Surface Movement Guidance and Control System (SMGCS) plan for : U.S. airports where scheduled Air Carriers are authorized to conduct operations : when...

Signal Waveform Detection with Statistical Automaton for Internet and Web Service Streaming

PubMed Central

Liu, Yiming; Huang, Nai-Lun; Zeng, Fufu; Lin, Fang-Ying

2014-01-01

In recent years, many approaches have been suggested for Internet and web streaming detection. In this paper, we propose an approach to signal waveform detection for Internet and web streaming, with novel statistical automatons. The system records network connections over a period of time to form a signal waveform and compute suspicious characteristics of the waveform. Network streaming according to these selected waveform features by our newly designed Aho-Corasick (AC) automatons can be classified. We developed two versions, that is, basic AC and advanced AC-histogram waveform automata, and conducted comprehensive experimentation. The results confirm that our approach is feasible and suitable for deployment. PMID:25032231

Thermoplastic-based conductive composites containing multi-wall carbon nanotubes aligned under the application of external electric fields

NASA Astrophysics Data System (ADS)

Osazuwa, Osayuki

The objective of this thesis is to prepare thermoplastic/multi-wall carbon nanotubes (MWCNTs) and to apply external alternating current (AC) electric fields to achieve enhanced conductivity and dielectric properties. The first part of the thesis focuses on preparing polyolefin-based composites containing welldispersed MWCNTs. MWCNTs are functionalized with a hyperbranched polyethylene (HBPE) using a non-covalent, non-specific functionalization approach and melt compounded with an ethylene-octene copolymer (EOC) matrix. The improved filler dispersion in the functionalized EOC/MWCNT composite results in higher elongation at break compared to the non-functionalized composite. However, the electrical percolation threshold and the ultimate conductivity of the composites are not affected considerably, suggesting that this functionalization approach leaves the inherent properties of the nanotubes intact. EOC/HBPE-functionalized MWCNT composites are further subjected to external AC electric fields (35 -- 212 kV/m), which induce the formation of aligned columnar structures, as evidenced by Scanning Electron Microscopy. Experimentally acquired resistivity data are used to derive correlations between the characteristic insulator-to-conductor transition times of the composites and the electric field strength (E), polymer viscosity (eta) and MWCNT volume fraction (φ). A criterion for the selection of (eta, E, φ) conditions that enable MWCNT assembly under an electric field controlled regime (minimal Brownian motion-driven aggregation effects) is developed. The dielectric properties of the solidified aligned EOC/MWCNT composites are further studied using dielectric spectroscopy. Annealing of the composites at 160 °C results in the formation of interconnected structures, whereas electrification, using AC field of 71 and 212 kV/m induces the formation of aligned columnar structures. The electrified and annealed composites have increased real and imaginary permittivity compared to the as-compounded composite, resulting in improved conductivity and storage capacity. An equivalent circuit model is fitted to the experimentally obtained impedance data in order to correlate the effects of electric field and processing time to the dielectric characteristics of the treated composites. Finally poly(ethylene succinate) (PESu) composites containing well-dispersed MWCNT were prepared by an in-situ polymerization method. Composite electrification results in improvements in the electrical conductivity by up to 12 orders of magnitude, and a retention of high conductivity in the solidified state.

Investigation of flux penetration in YBa 2Cu 3O 7-δ filaments

NASA Astrophysics Data System (ADS)

Devos, P.; Buekenhoudt, A.; D'Anna, G.; André, M.-O.; Indenbom, M. V.; Benoit, W.; De Batist, R.; Cornelis, J.

1994-12-01

ac Susceptibility measurements using a low frequency torsion pendulum and an ac susceptometer were conducted on YBa 2Cu 3O 7-δ filaments in low magnetic dc fields (≤1T). Different dissipation peaks are observed, dependent on the temperature and the applied amplitude. The peak at low temperatures, which is of intergranular nature is studied in detail. The penetration follows the Bean model and the intergranular creep is observed.

Systems and methods for creation of conducting networks of magnetic particles through dynamic self-assembly process

DOEpatents

Snezhko, Oleksiy [Woodridge, IL; Aronson, Igor [Darien, IL; Kwok, Wai-Kwong [Downers Grove, IL

2011-01-25

Self-assembly of magnetic microparticles in AC magnetic fields. Excitation of the system by an AC magnetic field provides a variety of patterns that can be controlled by adjusting the frequency and the amplitude of the field. At low particle densities the low-frequency magnetic excitation favors cluster phase formation, while high frequency excitation favors chains and netlike structures. For denser configurations, an abrupt transition to the network phase was obtained.

U.S. Special Operations Forces (SOF): Background and Issues for Congress

DTIC Science & Technology

2016-04-08

platforms to include AC-130U, AC-130W, U-28, MQ-1, MQ-9, C-145, C-146 as well as small unmanned aerial systems ( SUAS ), Combat Aviation Advisors, medical...forces can operate in small groups and have the ability to quickly deploy from Navy ships, submarines and aircraft , overseas bases, and forward-based...given greater responsibility for planning and conducting worldwide counterterrorism operations. U.S. Special Operations Command (USSOCOM) has about

Sustainability analysis using FORSEE and continuous forest inventory information to compare volume estimation methods for the Valencia coast redwood tract in Santa Cruz County, California

Treesearch

Douglas D. Piirto; Mitchell Haydon; Steve Auten; Benjamin Han; Samantha Gill; Wally Mark; Dale Holderman

2017-01-01

The 1,295 ha (3,200 ac) Swanton Pacific Ranch (Swanton) and the associated Valencia Tract in Santa Cruz County have been managed by California Polytechnic State University, San Luis Obispo (Cal Poly) since 1987. Swanton’s Valencia Tract is a 239 ha (591 ac) property located north of Watsonville, California. Cal Poly forest managers have conducted two harvest...

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. © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Thermal, dielectric characteristics and conduction mechanism of azodyes derived from quinoline and their copper complexes.

PubMed

El-Ghamaz, N A; Diab, M A; El-Bindary, A A; El-Sonbati, A Z; Nozha, S G

2015-05-15

A novel series of (5-(4'-derivatives phenyl azo)-8-hydroxy-7-quinolinecarboxaldehyde) (AQLn) (n=1, p-OCH3; n=2, R=H; and n=3; p-NO2) and their complexes [Cu(AQLn)2]·5H2O are synthesized and investigated. The optimized bond lengths, bond angles and the calculated quantum chemical parameters for AQLn are investigated. HOMO-LUMO energy gap, absolute electronegativities, chemical potentials, and absolute hardness are also calculated. The thermal properties, dielectric properties, alternating current conductivity (σac) and conduction mechanism are investigated in the frequency range 0.1-100kHz and temperature range 293-568K for AQL1-3 and 318-693K for [Cu(AQL1-3)2]·5H2O complexes. The thermal properties are of ligands (AQLn) and their Cu(II) complexes investigated by thermogravimetric analysis (TGA). The temperature and frequency dependence of the real and the imaginary part of the dielectric constant are studied. The values of the thermal activation energy of conduction mechanism for AQLn and their complexes [Cu(AQLn)2]·5H2O under investigation are calculated at different test frequencies. The values of thermal activation energies ΔE1 and ΔE2 for AQLn and [Cu(AQLn)2]·5H2O decrease with increasing the values of frequency. The ac conductivity is found to be depending on the chemical structure of the compounds. Different conduction mechanisms have been proposed to explain the obtained experimental data. The small polaron tunneling (SPT) is the dominant conduction mechanism for AQL1 and its complex [Cu(AQL1)2]·5H2O. The quantum mechanical tunneling (QMT) is the dominant conduction mechanism for AQL2 and its complex [Cu(AQL2)2]·5H2O. The correlated barrier hopping (CBH) is the dominant conduction mechanism for AQL3 and its complex [Cu(AQL3)2]·5H2O, and the values of the maximum barrier height (Wm) are calculated. Copyright © 2015 Elsevier B.V. All rights reserved.

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. Copyright © 2015 Elsevier Ltd. All rights reserved.

Powder X-ray diffraction, infrared and conductivity studies of AgSbMP{sub 3}O{sub 12} (M = Al, Ga, Fe and Cr)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rambabu, G.; Anantharamulu, N.; Koteswara Rao, K.

2008-06-03

New Nasicon type of compounds of composition AgSbMP{sub 3}O{sub 12} (M = Al, Ga, Fe and Cr) are synthesized by solid-state method. All the compounds crystallize in the hexagonal lattice with space group R3-barc. The infrared spectra of these compounds show characteristic bands due to PO{sub 4} group. The frequency independent conductivity of these compounds shows Arrhenius type behavior and the activation energy for conduction is in the range 0.40-0.55 eV. Frequency independent conductivity ({sigma}{sub dc}) studies and frequency dependent ({sigma}{sub ac}) impedance measurements correlate well. The Cole-Cole plots do not show any spikes on the lower frequency side indicatingmore » negligible electrode effects. The activation energies obtained from the plots of log {sigma}{sub dc}T versus 1/T, log {sigma}{sub ac}(0) versus 1/T and log {tau} versus 1/T are approximately the same. The peak width at half height for electric modulus (M'') plot is {approx}1.24 decades for all samples, which is close to 1.14 decades observed for Debye solid. The height of electric modulus (M'') obtained from the experimental plots are close to that of M'' (max) = C{sub 0}/2C indicating the Debye nature of the samples.« less

Preparation and characterization of MWCNT nanofiller incorporated polymer composite for lithium battery applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pradeepa, P.; Raj, S. Edwin; Selvakumar, K.

Poly (ethyl methacrylate) based polymer electrolyte films were prepared by solution casting technique incorporating multi-walled carbon nanotube (MWCNT) as filler and characterized using XRD and Ac impedance analysis. The electrical conductivity is increased with increasing filler concentration (upto 6wt %), which is attributed to the formation of charge transfer complexes. The maximum ionic conductivity value is found to be 1.171×10{sup −3} Scm{sup −1} at 303K for PEMA (19wt %) -LiClO{sub 4} (8wt %) -MWCNT (6wt %) -PC (67wt %) electrolyte system. The temperature dependent ionic conductivity plot seems to obey Vogel -Tamman-Fulcher relation.

Preparation, characterization and conductivity study of nitro-mercurated styrene butadiene rubber/silver doped zinc oxide nanocomposites

NASA Astrophysics Data System (ADS)

Anilkumar, T.; Naik, Adarsh Ajith; Ramesan, M. T.

2017-06-01

Here we report the preparation of nitromercurated styrene butadiene rubber (NMSBR)/silver doped zinc oxide nanocomposite by inexpensive and ecofriendly two roll mill mixing. The composites were characterized by UV, FTIR, XRD, SEM, TGA and conductivity measurements. UV and FTIR spectrum indicated the interfacial interaction between the polymer and nanoparticles.XRD and SEM images showed the uniform arrangement of nanoparticles within the macromolecular chain. TGA study indicated the better thermal resistance of the composite. The dielectric properties and AC conductivity ofnanocomposites were much greater than nitromercurated SBR and they may be used as multifunctional materials for nanoelectronic devices.

A scanning tunneling microscope break junction method with continuous bias modulation.

PubMed

Beall, Edward; Yin, Xing; Waldeck, David H; Wierzbinski, Emil

2015-09-28

Single molecule conductance measurements on 1,8-octanedithiol were performed using the scanning tunneling microscope break junction method with an externally controlled modulation of the bias voltage. Application of an AC voltage is shown to improve the signal to noise ratio of low current (low conductance) measurements as compared to the DC bias method. The experimental results show that the current response of the molecule(s) trapped in the junction and the solvent media to the bias modulation can be qualitatively different. A model RC circuit which accommodates both the molecule and the solvent is proposed to analyze the data and extract a conductance for the molecule.

Induction voidmeter

DOEpatents

Anderson, T.T.; Roop, C.J.; Schmidt, K.J.; Brewer, J.

1983-12-21

An induction voidmeter for detecting voids in a conductive fluid may comprise: a four arm bridge circuit having two adjustable circuit elements connected as opposite arms of said bridge, an input branch, and an output branch; two induction coils, bifilarly wound together, connected as the remaining two opposing arms of said bridge circuit and positioned such that the conductive fluid passes through said coils; means for applying an AC excitation signal to said input branch; and means for detecting the output signal generated in response to said excitation signal across said output branch. The induction coils may be located outside or inside a non-magnetic pipe containing the conductive fluid.

Nanoscale CuO solid-electrolyte-based conductive-bridging, random-access memory cell with a TiN liner

NASA Astrophysics Data System (ADS)

Lee, Jong-Sun; Kim, Dong-Won; Kim, Hea-Jee; Jin, Soo-Min; Song, Myung-Jin; Kwon, Ki-Hyun; Park, Jea-Gun; Jalalah, Mohammed; Al-Hajry, Ali

2018-01-01

The Conductive-bridge random-access memory (CBRAM) cell is a promising candidate for a terabit-level non-volatile memory due to its remarkable advantages. We present for the first time TiN as a diffusion barrier in CBRAM cells for enhancing their reliability. CuO solid-electrolyte-based CBRAM cells implemented with a 0.1-nm TiN liner demonstrated better non-volatile memory characteristics such as 106 AC write/erase endurance cycles with 100-μs AC pulse width and a long retention time of 7.4-years at 85 °C. In addition, the analysis of Ag diffusion in the CBRAM cell suggests that the morphology of the Ag filaments in the electrolyte can be effectively controlled by tuning the thickness of the TiN liner. These promising results pave the way for faster commercialization of terabit-level non-volatile memories.

Terahertz conductivity of twisted bilayer graphene

NASA Astrophysics Data System (ADS)

Chia, Elbert E. M.; Zou, Xingquan; Shang, Jingzhi; Leaw, Jianing; Luo, Zhiqiang; Luo, Liyan; Cheong, Siew Ann; Su, Haibin; Zhu, Jian-Xin; Castro Neto, A. H.; Yu, Ting

2013-03-01

Using terahertz time-domain spectroscopy, the real part of optical conductivity [σ1 (ω) ] of twisted bilayer graphene was obtained at different temperatures (10 - 300 K) in the frequency range 0.3 - 3 THz. On top of a Drude-like response, we see a strong and narrow peak in σ1 (ω) at ~2.7 THz. We analyze the overall Drude-like response using a disorder-dependent (unitary scattering) model, then attribute the peak at 2.7 THz to an enhanced density of states at that energy, that is caused by the presence of van Hove singularities arising from a commensurate twisting of the two graphene layers. Singapore MOE AcRF Tier 2 (ARC 23/08), NRF-CRP (NRF-CRP4-2008-04), NNSA of the U.S. DOE at LANL (DE-AC52-06NA25396), LANL LDRD Program, NRF-CRP (R-144-000-295-281), DOE DE-FG02-08ER46512, ONR MURI N00014-09-1-1063.

Characteristics of dielectric properties and conduction mechanism of TlInS2:Cu single crystals

NASA Astrophysics Data System (ADS)

El-Nahass, M. M.; Ali, H. A. M.; El-Zaidia, E. F. M.

2013-12-01

Single crystals of TlInS2:Cu were grown by the modified Bridgman method. The dielectric behavior of TlInS2:Cu was investigated using the impedance spectroscopy technique. The real (ε1), imaginary (ε2) parts of complex dielectric permittivity and ac conductivity were measured in the frequency range (42-2×105) Hz with a variation of temperature in the range from 291 K to 483 K. The impedance data were presented in Nyquist diagrams for different temperatures. The frequency dependence of σtot (ω) follows the Jonscher's universal dynamic law with the relation σtot (ω)=σdc+Aωs, (where s is the frequency exponent). The mechanism of the ac charge transport across the layers of TlInS2:Cu single crystals was referred to the hopping over localized states near the Fermi level. The examined system exhibits temperature dependence of σac (ω), which showed a linear increase with the increase in temperature at different frequencies. Some parameters were calculated as: the density of localized states near the Fermi level, NF, the average time of charge carrier hopping between localized states, τ, and the average hopping distance, R.

Structure dependent electrical properties of Ni-Mg-Cu nano ferrites

DOE Office of Scientific and Technical Information (OSTI.GOV)

Choudhari, Nagabhushan J., E-mail: nagabhushanchoudhari@gmail.com; Kakati, Sushanth S.; Hiremath, Chidanandayya S.

2016-05-06

Nano ferrites with the general chemical formula Ni{sub 0.5}Mg{sub x}Cu{sub 1-x} Fe{sub 2}O{sub 4} were synthesized by chemical route. They were characterized by x-ray diffraction by powder method. The diffraction patterns confirm the formation of single phase ferrites. The particle size is calculated by Scherrer formula which varies between 20nm to 60nm. DC resistivity was measured as a function of composition from room temperature to 700{sup o} C by two probe method. These ferrites show higher resistivity than those synthesized by ceramic method, due to control over composition and morphology. This leads to the elimination of domain wall resonance somore » that the materials can work at higher frequencies. AC resistivity was measured as a function of frequency at room temperature. Dielectric dispersion obeys Maxwell - Wagner model, in accordance with Koop’s phenomenological theory. The variation of loss angle follows the variation of ac resistivity with frequency and composition. The change in ac conductivity with frequency obeys the power law σ{sub a} = B.ω{sup n}. Such a behavior suggests that conductivity is due to polarons in all the samples.« less

Influence of Electric Fields and Conductivity on Pollen Tube Growth assessed via Electrical Lab-on-Chip

PubMed Central

Agudelo, Carlos; Packirisamy, Muthukumaran; Geitmann, Anja

2016-01-01

Pollen tubes are polarly growing plant cells that are able to rapidly respond to a combination of chemical, mechanical, and electrical cues. This behavioural feature allows them to invade the flower pistil and deliver the sperm cells in highly targeted manner to receptive ovules in order to accomplish fertilization. How signals are perceived and processed in the pollen tube is still poorly understood. Evidence for electrical guidance in particular is vague and highly contradictory. To generate reproducible experimental conditions for the investigation of the effect of electric fields on pollen tube growth we developed an Electrical Lab-on-Chip (ELoC). Pollen from the species Camellia displayed differential sensitivity to electric fields depending on whether the entire cell or only its growing tip was exposed. The response to DC fields was dramatically higher than that to AC fields of the same strength. However, AC fields were found to restore and even promote pollen growth. Surprisingly, the pollen tube response correlated with the conductivity of the growth medium under different AC frequencies—consistent with the notion that the effect of the field on pollen tube growth may be mediated via its effect on the motion of ions. PMID:26804186

Defined-size DNA triple crossover construct for molecular electronics: modification, positioning and conductance properties.

PubMed

Linko, Veikko; Leppiniemi, Jenni; Paasonen, Seppo-Tapio; Hytönen, Vesa P; Toppari, J Jussi

2011-07-08

We present a novel, defined-size, small and rigid DNA template, a so-called B-A-B complex, based on DNA triple crossover motifs (TX tiles), which can be utilized in molecular scale patterning for nanoelectronics, plasmonics and sensing applications. The feasibility of the designed construct is demonstrated by functionalizing the TX tiles with one biotin-triethylene glycol (TEG) and efficiently decorating them with streptavidin, and furthermore by positioning and anchoring single thiol-modified B-A-B complexes to certain locations on a chip via dielectrophoretic trapping. Finally, we characterize the conductance properties of the non-functionalized construct, first by measuring DC conductivity and second by utilizing AC impedance spectroscopy in order to describe the conductivity mechanism of a single B-A-B complex using a detailed equivalent circuit model. This analysis also reveals further information about the conductivity of DNA structures in general.

The Effect of Structural Modifications on Ionic Conductivity in Newly-Designed Polyester Electrolytes

NASA Astrophysics Data System (ADS)

Pesko, Danielle; Jung, Yuki; Coates, Geoff; Balsara, Nitash

2015-03-01

Gaining a fundamental understanding of the relationship between molecular structure and ionic conductivity of polymer electrolytes is an essential step toward designing next generation materials for battery applications. In this study, we use a systematic set of newly-designed polyesters with varying side-chain lengths and oxygen functional groups to elucidate the effects of structural modifications on the conductive properties of the corresponding electrolytes. Mixtures of polyesters and lithium bis(trifluromethanesulfonyl)imide (LiTFSI) were characterized using ac impedance spectroscopy to measure the ionic conductivity at various temperatures and salt concentrations. The relative conductivities of these electrolytes in the dilute limit are directly comparable to results of molecular dynamics simulations performed using the same polymers. The simulations correspond well with the experimental results, and provide molecular level insight about the solvation environment of the lithium ions and how the ions transport through these polyesters.

Protonic Conduction of BaCe0.85YO. 1503 Doped with SrTiO3

NASA Technical Reports Server (NTRS)

Dynys, Frederick W.; Sayir, Ali

2005-01-01

Reformers based on ceramic membrane technology potentially offer hydrogen production that is comparable to the cost of fossil fuels. Protonic conducting ceramic with the chemical formula AB03 offers the promise of highly selective hydrogen separation at intermediate temperature (400-800 C). Among different perovskite-type oxides, BaCe03 and SrCe03 based compositions show high protonic conductivities but strong resistance to densification. X-ray diffraction studies on sintered specimens of BaCe0.85Y0.1503-6 show multi-phase formation which was found to show dependence upon powder synthesis method. Doping with SrTiO3 suppresses multi-phase formation and enhances grain growth. Conductivity measurements in temperature range of 200 to 1000 C were performed by ac impedance spectroscopy under dry and wet conditions. Sintering behavior, phase formation and conductivity results will be reported.

Swift heavy ion irradiation effects on structural, optical properties and ac conductivity of polypyrrole nanofibers

NASA Astrophysics Data System (ADS)

Hazarika, J.; Kumar, A.

2016-12-01

Polypyrrole (PPy) nanofibers have been synthesized by interfacial polymerization method and irradiated with 160 MeV Ni12+ ions under vacuum with fluences in the range of 1010-1012 ions/cm2. High-resolution transmission electron microscopy results show that upon swift heavy ion (SHI) irradiation the PPy nanofibers become denser. The crystallinity of PPy nanofibers increases upon SHI irradiation, while their d-spacing decreases. Upon SHI irradiation, the polaron absorption band gets red-shifted indicating reduction in the optical band gap energy of the irradiated PPy nanofibers. The indirect optical band gap energy is decreased as compared to corresponding direct optical band gap energy. The number of carbon atoms per conjugation length (N) and carbon atoms per cluster (M) of the SHI-irradiated PPy nanofibers increase with increasing the irradiation fluence. Fourier transform infrared spectra reveal the enhancement in intensity of some characteristic vibration bands upon SHI irradiation. The thermal stability of the PPy nanofibers is enhanced on SHI irradiation. The charge carriers in both pristine and irradiated PPy nanofibers follow the correlated barrier hopping mechanism. Scaling of ac conductivity reveals that the conduction mechanism is independent of the SHI irradiation fluence.

Determination of rock properties by low-frequency AC electrokinetics

NASA Astrophysics Data System (ADS)

Pengra, David B.; Xi Li, Sidney; Wong, Po-Zen

1999-12-01

In brine-saturated rock the existence of a mobile space charge at the fluid/solid interface leads to the electrokinetic phenomena of electroosmotic pressure and streaming potential. The coupling coefficients of these electrokinetic effects, when combined with the conductivity of the brine-saturated rock, determine the brine permeability of rock exactly. A sensitive low-frequency AC technique has been used to measure electrokinetic response of a collection of eight rock and four glass bead samples saturated with NaCl brine as a function of salt concentration (fluid conductivity of 0.5 to 6.38 S/m); the response of four of the original 12 samples has also been measured as a function of temperature from 0° to 50°C. All data verify the predicted permeability relationship. Additionally, the frequency response of the electroosmotic pressure signal alone can also be used to determine the permeability, given knowledge of experimental parameters. The concentration and temperature dependence of electroosmosis and streaming potential is found to mostly conform to the predictions of a simple model based on the Helmholtz-Smoluchowski equation, the Stern model of the electrochemical double layer, and an elementary theory of ionic conduction.

Selection and preliminary evaluation of three structures as potential solid conductors of alkali ions: Two hollandites, a titanate, and a tungstate

NASA Technical Reports Server (NTRS)

Singer, J.; Kautz, H. E.; Fielder, W. L.; Fordyce, J. S.

1973-01-01

Utilization of crystal-chemical criteria has suggested three structure types in which alkali ions may be mobile: (1)hollandites K(x)Mg(x/2)Ti(8-x/2)O16 and K(x)Al(x)Ti(8-x)O16 for 1.6 less than or equal to x less than or equal to 2.0 tungstate K2W4013; and (3) sodium hexatitante Na2Ti6O13. Each is a tunnel structure. An electrical screening procedure, previously tested on beta-alumina, has indicated high K(+) ion mobility in the hollandites and in the tungstate, but not in the hexatitanate. Specimens were polycrystalline disks near 90 percent of theoretical density. The ac conductivity calculated from dielectric and capacitance measurements has been attributed to ion mobility. This ac conductivity was up to 0.01/ohm-cm for hollandites and about 0.0001/ohm-cm for the tungstate, with approximate activation energies of 21 to 25 and 16 kJ/mole (5 to 6 and 4 kcal/mole), respectively. Electronic conduction and chemical reactivity have eliminated the tungstate from further consideration. The hollandites have been considered worthy of further development and evaluation.

Anisotropic superconductivity in β-(BDA-TTP)2SbF6: STM spectroscopy

NASA Astrophysics Data System (ADS)

Nomura, K.; Muraoka, R.; Matsunaga, N.; Ichimura, K.; Yamada, J.

2009-03-01

We have investigated the gap symmetry in the superconducting phase of β-(BDA-TTP)2SbF6 with use of the scanning tunneling microscope (STM). The tunneling spectra obtained on the conducting surface show a clear superconducting gap structure. Its functional form is of V-shaped similarly to κ-(BEDT-TTF)2X and suggests the anisotropic superconducting gap with line nodes. For lateral surfaces the shape of tunneling spectra varies from the U-shape with relatively large gap to the V-shape with small gap depending on the tunneling direction alternately twice between directional angle 0 and π. From the analysis of conductance curve taking the k dependence of the tunneling probability into account, it is found that the gap has maximum near the a* and c* axes and the nodes appear along near a*+c* and the a-c* directions. These indicate that the d like superconducting pair is formed in this system as the case of κ-(BEDT-TTF)2X. This node direction is consistent with the theoretical prediction based on the spin fluctuation mechanism. However, the zero-bias conductance peak has not been observed yet.

Multiferroic properties of microwave sintered PbFe12-xO19-δ

NASA Astrophysics Data System (ADS)

Prathap, S.; Madhuri, W.

2017-05-01

The effect of iron deficiency on the structural, electrical, ferroelectric and magnetic properties of nano PbFe12-xO19-δ (where x=0.0, 0.25, 0.50, 0.75, 1.0) hexaferrites prepared by sol-gel auto combustion and processed by microwaves are investigated. X-ray analysis confirms single phase magneto-plumbite phase formation. The surface morphology is studied from Field Emission Scanning Electron Microscope. Further, optical properties are investigated using Fourier Transform Infrared spectra and UV-visible spectra. AC electrical conductivity is estimated as a function of temperature and frequency in the range of room temperature (RT) to 500 °C and 100 Hz to 5MHz. AC electrical conduction analysis shows that conduction is mainly due to small polaron hopping mechanism. The variation of polarization with applied electric field exhibits hysteresis loop confirming the ferroelectric nature. The initial permeability studies with varying temperature reveals that the Curie transition temperature for the present series is around 400 °C. Variation of initial permeability with frequency ranging from 100 to 5 MHz shows a constant value (except for x=0.0) opening avenues for high frequency applications.

[Serological affinity of some species of nonpathogenic corynebacteria].

PubMed

Furtat, I M; Nohina, T M; Mikhal's'kyĭ, L O; Vedenieieva, O A

2002-01-01

Serological peculiarities of the species strains Corynebacterium glutamicum, C. ammoniagenes, C. vitaeruminis, C. variabilis and strain of Corynebacterium sp. (Brevibacterium stationis) UCM Ac-719 have been investigated with the help of immunoenzyme analysis ELISA with the use of mice immune serum, specific to C. ammoniagenes UCM Ac-732T, C. vitaeruminis UCM Ac-718T, C. variabilis UCM Ac-717T, C. glutamicum UCM Ac-733 and Corynebacterium sp. UCM Ac-719. It has been established that the species of nonpathogenic corynebacteria differ between themselves as to the degree of serological affinity. C. variabilis, C. ammoniagenes and C. glutamicum are the least similar as to this indication. Weak antigenic relations have been revealed in C. vitaeruminis and C. ammoniagenes. The latter displayed the higher, as compared with other strains, affinity for Corynebacterium sp. UCM Ac-719. The highest degree of serological affinity within the species was registered in strains C. glutamicum and C. variabilis. Data obtained evidence that the ELISA method permits conducting the high-reliability species diagnosis of nonpathogenic corynebacteria on the basis of their antigenic characteristics.

High surface area bio-waste based carbon as a superior electrode for vanadium redox flow battery

NASA Astrophysics Data System (ADS)

Maharjan, Makhan; Bhattarai, Arjun; Ulaganathan, Mani; Wai, Nyunt; Oo, Moe Ohnmar; Wang, Jing-Yuan; Lim, Tuti Mariana

2017-09-01

Activated carbon (AC) with high surface area (1901 m2 g-1) is synthesized from low cost bio-waste orange (Citrus sinensis) peel for vanadium redox flow battery (VRB). The composition, structure and electrochemical properties of orange peel derived AC (OP-AC) are characterized by elemental analyzer, field emission-scanning electron microscopy, X-ray diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy, cyclic voltammetry (CV), and electrochemical impedance spectroscopy. CV results show that OP-AC coated bipolar plate demonstrates improved electro-catalytic activity in both positive and negative side redox couples than the pristine bipolar plate electrode and this is ascribed to the high surface area of OP-AC which provides effective electrode area and better contact between the porous electrode and bipolar plate. Consequently, the performance of VRB in a static cell shows higher energy efficiency for OP-AC electrode than the pristine electrode at all current densities tested. The results suggest the OP-AC to be a promising electrode for VRB applications and can be incorporated into making conducting plastics electrode to lower the VRB cell stack weight and cost.

Treatment of simulated wastewater containing Reactive Red 195 by zero-valent iron/activated carbon combined with microwave discharge electrodeless lamp/sodium hypochlorite.

PubMed

Fu, Jie; Xu, Zhen; Li, Qing-Shan; Chen, Song; An, Shu-Qing; Zeng, Qing-Fu; Zhu, Hai-Liang

2010-01-01

A comparative study of treatment of simulated wastewater containing Reactive Red 195 using zero-valent iron/activated carbon (ZVI/AC), microwave discharge electrodeless lamp/sodium hypochlorite (MDEL/NaClO) and the combination of ZVI/AC-MDEL/NaClO was conducted. The preliminary results showed the two steps method of ZVI/AC-MDEL/NaClO had much higher degradation efficiency than both single steps. The final color removal percentage was nearly up to 100% and the chemical oxygen demand reduction percentage was up to approximately 82%. The effects of operational parameters, including initial pH value of simulated wastewater, ZVI/AC ratio and particle size of ZVI were also investigated. In addition, from the discussion of synergistic effect between ZVI/AC and MEDL/NaClO, we found that in the ZVI/AC-MEDL/NaClO process, ZVI/AC could break the azo bond firstly and then MEDL/NaClO degraded the aromatic amine products effectively. Reversing the order would reduce the degradation efficiency.

Novel Nd 2WO 6-type Sm 2- xA xM 1- yB yO 6- δ (A = Ca, Sr; M = Mo, W; B = Ce, Ni) mixed conductors

NASA Astrophysics Data System (ADS)

Li, Qin; Thangadurai, Venkataraman

In the present work, we have explored novel Nd 2WO 6-type structure Sm 2- xA xM 1- yB yO 6- δ (A = Ca, Sr; M = Mo, W; B = Ce, Ni) as precursor for the development of solid oxide fuel cells (SOFCs) anodes. The formation of single-phase monoclinic structure was confirmed by powder X-ray diffraction (PXRD) for the A- and B-doped Sm 2MO 6 (SMO). Samples after AC measurements under wet H 2 up to 850 °C changed from Nd 2WO 6-type structure into Sm 2MoO 5 due to the reduction of Mo VI that was confirmed by PXRD and is consistent with literature. The electrical conductivity was determined using 2-probe AC impedance and DC method and was compared with 4-probe DC method. The total electrical conductivity obtained from these two different techniques was found to vary within the experimental error over the investigated temperature of 350-650 °C. Ionic and electronic conductivity were studied using electron-blocking electrodes technique. Among the samples studied, Sm 1.8Ca 0.2MoO 6- δ exhibits total conductivity of 0.12 S cm -1 at 550 °C in wet H 2 with an activation energy of 0.06 eV. Ca-doped SMO appears to be chemically stable against reaction with YSZ electrolyte at 800 °C for 24 h in wet H 2. The ionic transference number (t i) of Sm 1.9Ca 0.1MoO 6- δ in wet H 2 at 550 °C (pO 2 = 10 -25.5 atm) was found to be about 0.012 after subtraction of electrical lead resistance from the 2-probe AC data and showed predominate electronic conductors.

Single-channel measurements of an N-acetylneuraminic acid-inducible outer membrane channel in Escherichia coli

PubMed Central

Giri, Janhavi; Tang, John M.; Wirth, Christophe; Peneff, Caroline M.

2012-01-01

NanC is an Escherichia coli outer membrane protein involved in sialic acid (Neu5Ac, i.e., N-acetylneuraminic acid) uptake. Expression of the NanC gene is induced and controlled by Neu5Ac. The transport mechanism of Neu5Ac is not known. The structure of NanC was recently solved (PDB code: 2WJQ) and includes a unique arrangement of positively charged (basic) side chains consistent with a role in acidic sugar transport. However, initial functional measurements of NanC failed to find its role in the transport of sialic acids, perhaps because of the ionic conditions used in the experiments. We show here that the ionic conditions generally preferred for measuring the function of outer-membrane porins are not appropriate for NanC. Single channels of NanC at pH 7.0 have: (1) conductance 100 pS to 800 pS in 100 mM KCl to 3 M KCl), (2) anion over cation selectivity (Vreversal = +16 mV in 250 mM KCl || 1 M KCl), and (3) two forms of voltage-dependent gating (channel closures above ±200 mV). Single-channel conductance decreases by 50% when HEPES concentration is increased from 100 μM to 100 mM in 250 mM KCl at pH 7.4, consistent with the two HEPES binding sites observed in the crystal structure. Studying alternative buffers, we find that phosphate interferes with the channel conductance. Single-channel conductance decreases by 19% when phosphate concentration is increased from 0 mM to 5 mM in 250 mM KCl at pH 8.0. Surprisingly, TRIS in the baths reacts with Ag|AgCl electrodes, producing artifacts even when the electrodes are on the far side of agar–KCl bridges. A suitable baseline solution for NanC is 250 mM KCl adjusted to pH 7.0 without buffer. PMID:22246445

Increasing ion sorption and desorption rates of conductive electrodes

DOEpatents

DePaoli, David William; Kiggans, Jr., James O; Tsouris, Costas; Bourcier, William; Campbell, Robert; Mayes, Richard T

2014-12-30

An electrolyte system includes a reactor having a pair of electrodes that may sorb ions from an electrolyte. The electrolyte system also includes at least one power supply in electrical communication with the reactor. The at least one power supply may supply a DC signal and an AC signal to the pair of electrodes during sorption of the ions. In addition, the power supply may supply only the AC signal to the pair of electrodes during desorption of the ions.

Dwell Time and Surface Parameter Effects on Removal of Silicone Oil From D6ac Steel Using TCA

NASA Technical Reports Server (NTRS)

Boothe, R. E.

2003-01-01

This study was conducted to evaluate the impact of dwell time, surface roughness, and the surface activation state on 1,1,1-trichloroethane's (TCA's) effectiveness for removing silicone oil from D6ac steel. Silicone-contaminated test articles were washed with TCA solvent, and then the surfaces were analyzed for residue, using Fourier transform infrared spectroscopy. The predominant factor affecting the ability to remove the silicone oil was surface roughness.

Density-matrix renormalization group method for the conductance of one-dimensional correlated systems using the Kubo formula

NASA Astrophysics Data System (ADS)

Bischoff, Jan-Moritz; Jeckelmann, Eric

2017-11-01

We improve the density-matrix renormalization group (DMRG) evaluation of the Kubo formula for the zero-temperature linear conductance of one-dimensional correlated systems. The dynamical DMRG is used to compute the linear response of a finite system to an applied ac source-drain voltage; then the low-frequency finite-system response is extrapolated to the thermodynamic limit to obtain the dc conductance of an infinite system. The method is demonstrated on the one-dimensional spinless fermion model at half filling. Our method is able to replicate several predictions of the Luttinger liquid theory such as the renormalization of the conductance in a homogeneous conductor, the universal effects of a single barrier, and the resonant tunneling through a double barrier.

Processing and electrical properties of gallium-substituted lead zirconate titanate ceramics

NASA Astrophysics Data System (ADS)

Hajra, Sugato; Sharma, Pulkit; Sahoo, Sushrisangita; Rout, P. K.; Choudhary, R. N. P.

2017-12-01

In the present paper, the effect of gallium (Ga) substitution on structural, microstructural, electrical conductivity of Pb(ZrTi)O3 (PZT) in the morphotropic phase boundary (MPB) region (i.e., Pb0.96Ga0.04(Zr0.48Ti0.52)0.99O3 (PGaZT-4)) was investigated. Increased grain density increases the resistivity of the Ga-modified PZT system. Preliminary structural analysis using X-ray diffraction pattern and data showed the existence of two phases [major tetragonal (T) and minor monoclinic (M)]. Field emission scanning electron micrograph (FESEM) showed the distribution of spherical as well as platelet type grains with small pores. The behavior of dielectric constant with temperature of PGaZT-4 exhibited the suppression of the ferroelectric phase transition [i.e., disappearance of Curie temperature ( T c)]. The complex impedance spectroscopy (CIS) technique helped to investigate the impedance parameters of PGaZT-4 in MPB region in a wide range of temperature (250-500 °C) and frequency (1-1000 kHz) region. The impedance parameters of the material are found to be strongly dependent on frequency of AC electric field and temperature. The substitution of gallium at the Pb site of PZT generally enhances the dielectric constant and decreases loss tangent. The AC conductivity vs frequency ( f = ω2 π) in the region of dispersion follows the universal response of Jonscher's equation. Enhanced resistive characteristics were observed for Ga-substituted PZT in comparison to the pure PZT, which was well ensured from the studies of electrical parameters, such as impedance and AC conductivity.

Characterisation of Nd2O3 thick gate dielectric for silicon

NASA Astrophysics Data System (ADS)

Dakhel, A. A.

2004-03-01

Thin neodymium films were prepared by the reactive synthesis method on Si (P) substrates to form MOS devices. The oxide films were characterised by UV absorption spectroscopy, X-ray fluorescence (EDXRF) and X-ray diffraction (XRD). The ac conductance and capacitance of the devices were studied as a function of frequency in the range 100 Hz-100 kHz, of temperature in the range 293-473 K and of gate voltage. It was proved that a suitable formalism to explain the frequency dependence of the ac conductivity and capacitance of the insulator is controlled by a universal power law based on the relaxation processes of the hopping or tunnelling of the current carriers between equilibrium sites. The temperature dependence of the ac conductance at the accumulation state shows a small activation energy of about 0.07 eV for a MOS device with amorphous neodymium oxide. The temperature dependence of the accumulation capacitance for a MOS structure with crystalline neodymium oxide shows a maximum at about 390 K; such a maximum was not observed for the structure with amorphous neodymium oxide. The method of capacitance-gate voltage (C-Vg) measurements was used to investigate the effect of annealing in air and in vacuum on the surface density of states (Nss) at the insulator/semiconductor (I/S) interface. It was concluded that the density of surface states in the mid-gap increases by about five times while the density of the trapped charges in the oxide layer decreases by about eight times when the oxide crystallises into a polycrystalline structure.

Magnetic adsorbents for the removal of Hg (II) and phenanthrene from aqueous solutions

NASA Astrophysics Data System (ADS)

Isari, Ekavi; Karapanagioti, Hrissi K.; Manariotis, Ioannis D.; Werner, David

2015-04-01

Activated carbon (AC) acts as a strong binding agent that lowers the pollutant concentration and, thus its toxicity. Another promising sorbent material in environmental applications is biochar (BC) which is obtained from the incomplete combustion of carbon-rich biomass under oxygen-limited conditions. Both of these materials could be used as soil or sediment amendments that would lower the toxicity in the aqueous phase. A draw back of this technique is that although the pollutant will remain non- bioavailable for many years being sorbed into these sorbents, it actually stays into the system. The objective of this study was (a) to synthesize a magnetic powdered activated carbon (AC/Fe) and magnetic powdered biochar (BC/Fe) produced from commercial AC1 and AC2 samples and biochar respectively and (b) to evaluate the potential use of AC/Fe and BIO/Fe to remove aqueous Hg (II) or phenanthrene while being magnetically recoverable. The BC was produced from olive pomace. The surface area, the pore volume, and the average pore size of each sorbent were determined using gas (N2) adsorption-desorption cycles and the Brunauer, Emmett, and Teller (BET) equation. Isotherms with 30 adsorption and 20 desorption points were conducted at liquid nitrogen temperature (77K). Open surface area and micropore volume were determined using t-plot method and Harkins & Jura equation. For both AC/Fe, surface area measurements resulted in 66% those of corresponding AC. For BC/Fe, the surface area was 82% that of BC. Batch experiments with all sorbent samples and mercury solutions were conducted at room temperature (25oC) and at pH 5 in order to compare the sorption properties of the materials. Similar tests were performed with phenanthrene solutions. Based on mercury isotherm data, AC/Fe and BC/Fe are effective sorbents but with lower sorption capacity compared to the initial materials (50-75% lower). All these properties point to promising materials that can effectively be used for in-situ environmental remediation and also be recovered.

Marketing and transportation of grain by local cooperatives

DOT National Transportation Integrated Search

1993-11-01

This study focuses on first-handlers-of-grain cooperatives for the fiscal years ending in calendar year 1991. It is comparable with studies previously conducted by the Agricultural Cooperative Service covering 1985-86 (ACS Research Report 70), 1982-8...

Producing fluid flow using 3D carbon electrodes

NASA Astrophysics Data System (ADS)

Rouabah, H. A.; Park, B. Y.; Zaouk, R. B.; Madou, M. J.; Green, Nicolas G.

2008-12-01

Moving and manipulating bio-particles and fluids on the microscale is central to many lab-on-a-chip applications. Techniques for pumping fluids which use electric fields have shown promise using both DC and AC voltages. AC techniques, however, require the use of integrated metal electrodes which have a low resistance but can suffer from unwanted chemical reactions even at low potentials. In this paper we introduce the use of carbon MEMS technology (C-MEMS), a fabrication method which produces 3D conductive polymeric structures. Results are presented of the fabrication of an innovative design of 3D AC-electroosmotic micropump and preliminary experimental measurements which demonstrate the potential of both the technology and the design.

Dielectric Measurements on Sol-Gel Derived Titania Films

NASA Astrophysics Data System (ADS)

Capan, Rifat; Ray, Asim K.

2017-11-01

Alternating current (AC) impedance measurements were performed on 37 nm thick nanostructured sol-gel derived anatase titania films on ultrasonically cleaned (100) p-silicon substrates at temperatures T ranging from 100 K to 300 K over a frequency range between 20 Hz and 1 MHz. The frequency-dependent behavior of the AC conductivity σ ac( f, T) obeys the universal power law, and the values of the effective hopping barrier and hopping distance were found to be 0.79 eV and 6.7 × 10-11 m from an analysis due to the correlated barrier-hopping model. The dielectric relaxation was identified as a thermally activated non-Debye process involving an activation energy of 41.5 meV.

Linking results of key and supplementary comparisons of AC/DC voltage transfer references

NASA Astrophysics Data System (ADS)

Velychko, Oleh

2018-04-01

A regional key comparison (KC) COOMET.EM-K6.a and a supplementary comparison (SC) COOMET.EM-S1 of AC/DC voltage transfer references were conducted between participating laboratories from the Eurasian region. Measurements were made over the period 2004-2014. The results showed good agreement between all but one of the participating laboratories. The proposed procedure of linking results of key and SCs of regional metrology organization of AC/DC voltage transfer references is presented. Linking results is realized for COOMET.EM-K6.a and CCEM-K6.a KCs, and for COOMET.EM-K6.a KC and COOMET.EM-S1 SC.

The special features of the crystal structure and properties of oxides with mixed conductivity based on lanthanum gallate

NASA Astrophysics Data System (ADS)

Politova, E. D.; Ivanov, S. A.; Kaleva, G. M.; Mosunov, A. V.; Rusakov, V. S.

2008-10-01

The paper presents a review of works on the synthesis, structural composition effects, phase transitions, and electrical conductivity properties of multicomponent solid solutions based on heterosubstituted lanthanum gallate (La,A)(Ga,M)O3 - y . High-temperature phase transitions and structural and charge ordering effects were studied. The presence of iron cations in different valence states was proved; the relative contents of these cations depended on the x parameter and nonstoichiometry parameter y of the base composition. For M = Fe, antiferromagnetic ordering was observed; its temperature interval was determined by the concentration of iron cations in the high-spin state. The total conductivity was found to increase as the concentration of transition metal cations grew because of an increase in the electronic conductivity component. The data on structural parameters and dc and ac conductivity substantiated the conclusion that the highest ionic conductivity and permeability to oxygen were characteristic of iron-containing oxides. The results obtained are evidence that crystal chemical factors play a determining role in the formation of the ion-conducting properties of anion-deficient perovskite-like oxides.

Drinking Drivers and Drug Use on Weekend Nights in the United States*

PubMed Central

Voas, Robert B.; Lacey, John H.; Jones, Kristina; Scherer, Michael; Compton, Richard

2012-01-01

BACKGROUND Studies of drinking drivers in alcohol-related crashes have shown that high breath-alcohol concentrations (BrACs) are associated with illegal drug use. Until the 2007 National Roadside Survey (NRS), the prevalence of drugs among drinking drivers on U.S. roads was unknown. Using NRS data, we explore how many drivers with positive BrACs may also be using drugs and their significance to current drinking-driving enforcement procedures. METHODS Based on a stratified, random sample covering the 48 U.S. contiguous states, we conducted surveys on weekend nights from July-November 2007. Of the 8,384 eligible motorists contacted, 85.4% provided a breath sample; 70.0%, an oral fluid sample; and 39.1%, a blood sample. We conducted regression analyses on 5,912 participants with a breath test and an oral fluid or blood test. The dependent variables of interest were illegal drugs (cocaine, cannabinoids, street drugs, street amphetamines, and opiates) and medicinal drugs (prescription and over-the-counter). RESULTS 10.5% of nondrinking drivers were using illegal drugs, and 26 to 33% of drivers with illegal BrACs (≥.08 g/dL) were using illegal drugs. Medicinal drug use was more common among nondrinking drivers (4.0%) than among drivers with illegal BrACs (2.4%). CONCLUSIONS The significant relationship between an illegal BrAC and the prevalence of an illegal drug suggests as many as 350,000 illegal drug-using drivers are arrested each year for DWI by U.S. alcohol-impaired driving enforcement. These drug-using drivers need to be identified and appropriate sanctions/treatment programs implemented for them in efforts to extend per se laws to unapprehended drug users. PMID:23265090

Probing of the pseudogap via thermoelectric properties in the Au-Al-Gd quasicrystal approximant

NASA Astrophysics Data System (ADS)

Ishikawa, Asuka; Takagiwa, Yoshiki; Kimura, Kaoru; Tamura, Ryuji

2017-03-01

The pseudogap of the recently discovered Au-Al-Gd quasicrystal approximant crystal (AC) is investigated over a wide electron-per-atom (e /a ) ratio of ˜0.5 using thermoelectric properties as an experimental probe. This Au-Al-Gd AC provides an ideal platform for fine probing of the pseudogap among a number of known ACs because the Au-Al-Gd AC possesses an extraordinarily wide single-phase region with respect to the variation in the electron concentration [A. Ishikawa, T. Hiroto, K. Tokiwa, T. Fujii, and R. Tamura, Phys. Rev. B 93, 024416 (2016), 10.1103/PhysRevB.93.024416], in striking contrast to, for instance, binary stoichiometric C d6R ACs. As a result, a salient peak structure is observed in the Seebeck coefficient, S , with the composition as well as that of the power factor S2σ , in addition to a gradual variation in the conductivity, σ , and S . These two features are directly associated with rapid and slow variations, respectively, of spectral conductivity σ (E ) , and hence the fine structure inside the pseudogap, in the vicinity of the Fermi level EF. Based on the observed continuous variation of the Fermi wave vector reported in the previous experimental work, fine tuning of EF toward an optimal position was attempted, which led to the successful observation of a sharp peak in S2σ with a value of ˜270 μ W /m .K2 at 873 K. This is the highest value ever reported among both Tsai-type and Bergman-type compounds. The dimensionless figure of merit was determined as 0.026 at 873 K, which is also the highest reported among both Tsai-type and Bergman-type compounds.

Alternating current conduction studies on polypyrrole-iron nanocomposite at room temperature

NASA Astrophysics Data System (ADS)

Kumar, T. G. Naveen; Megha, R.; Revanasiddappa, M.; Ravikiran, Y. T.; Kumari, S. C. Vijaya

2018-05-01

In the present work, Polypyrrole (PPy) and Polypyrrole-Iron (PPy-Fe) nanocomposite were synthesized separately by chemical polymerisation method and then they were structurally characterised by Fourier transform infrared spectroscopy (FTIR) and Transmission electron microscopy (TEM) techniques. The alternate current (AC) response characteristics at room temperature of PPy and the composite were comparatively studied in the frequency range 100Hz-1MHz. The real part of conductivities of both PPy and the composite were interpreted as power law of frequency and the frequency exponent s was found to lie in the range 0< s<1 in both the cases. The nanocomposite has shown significant improvement in conductivity as compared to PPy.

Measuring and Modeling Organochlorine Pesticide Response to Activated Carbon Amendment in Tidal Sediment Mesocosms.

PubMed

Thompson, Jay M; Hsieh, Ching-Hong; Hoelen, Thomas P; Weston, Donald P; Luthy, Richard G

2016-05-03

Activated carbon (AC) sediment amendment for hydrophobic organic contaminants (HOCs) is attracting increasing regulatory and industrial interest. However, mechanistic and well-vetted models are needed. Here, we conduct an 18 month field mesocosm trial at a site containing dichlorodiphenyltrichloroethane (DDT) and chlordane. Different AC applications were applied and, for the first time, a recently published mass transfer model was field tested under varying experimental conditions. AC treatment was effective in reducing DDT and chlordane concentration in polyethylene (PE) samplers, and contaminant extractability by Arenicola brasiliensis digestive fluids. A substantial AC particle size effect was observed. For example, chlordane concentration in PE was reduced by 93% 6 months post-treatment in the powdered AC (PAC) mesocosm, compared with 71% in the granular AC (GAC) mesocosm. Extractability of sediment-associated DDT and chlordane by A. brasiliensis digestive fluids was reduced by at least a factor of 10 in all AC treatments. The model reproduced the relative effects of varying experimental conditions (particle size, dose, mixing time) on concentrations in polyethylene passive samplers well, in most cases within 25% of experimental observations. Although uncertainties such as the effect of long-term AC fouling by organic matter remain, the study findings support the use of the model to assess long-term implications of AC amendment.

The in vitro antibiotic release from anti-washout apatite cement using chitosan.

PubMed

Takechi, Masaaki; Miyamoto, Youji; Momota, Yukihiro; Yuasa, Tetsuya; Tatehara, Seikou; Nagayama, Masaru; Ishikawa, Kunio; Suzuki, Kazuomi

2002-10-01

The in vitro antibiotic release from anti-washout apatite cement using chitosan (aw-AC(chi)) was investigated in a preliminary evaluation. Flomoxef sodium was employed as the antibiotic and was incorporated into the powder phase aw-AC(chi) at up to 10%. The setting times were measured for aw-AC(chi) containing various amounts of flomoxef sodium. X-ray diffraction (XRD) analysis was also conducted for the identification of products. To evaluate the drug release profile, set aw-AC was immersed in saline and the released flomoxef sodium was determined at regular intervals. The setting time was prolonged slightly with the addition of flomoxef sodium. The difference at 10% flomoxef sodium (0% vs. 10%) was not significant (p>0.05), and can be negligible in clinic. The XRD analysis revealed that formation of hydroxyapatite (HAP) from aw-AC(chi) was reduced, even after 24 h, when the aw-AC(chi) contained flomoxef sodium at 8% or more. The flomoxef sodium release from aw-AC(chi) showed the typical profile observed in skeleton type drug delivery system (DDS). Changing the concentration of chitosan can control the rate of drug release from aw-AC. Therefore, we conclude that aw-AC(chi) is a good candidate for potential use as a DDS carrier that may be useful in surgical operations.

Horizontal electromagnetic casting of thin metal sheets

DOEpatents

Hull, John R.; Lari, Robert J.; Praeg, Walter F.; Turner, Larry R.

1987-01-01

Thin metal sheets are cast by magnetically suspending molten metal deposited within a ferromagnetic yoke and between AC conducting coils and linearly displacing the magnetically levitated liquid metal while it is being cooled to form a solid metal sheet. Magnetic flux increases as the molten metal sheet moves downward and decreases as the molten metal sheet moves upward to stabilize the sheet and maintain it in equilibrium as it is linearly displaced and solidified by cooling gases. A conducting shield is electrically coupled to the molten metal sheet by means of either metal sheet engaging rollers or brushes on the solidified metal, and by means of an electrode in the vessel containing the molten metal thereby providing a return path for the eddy currents induced in the metal sheet by the AC coil generated magnetic flux. Variation in the geometry of the conducting shield allows the magnetic flux between the metal sheet and the conducting shield to be varied and the thickness in surface quality of the metal sheet to be controlled. Side guards provide lateral containment for the molten metal sheet and stabilize and shape the magnetic field while a leader sheet having electromagnetic characteristics similar to those of the metal sheet is used to start the casting process and precedes the molten metal sheet through the magnet and forms a continuous sheet therewith. The magnet may be either U-shaped with a single racetrack coil or may be rectangular with a pair of facing bedstead coils.

Horizontal electromagnetic casting of thin metal sheets

DOEpatents

Hull, John R.; Lari, Robert J.; Praeg, Walter F.; Turner, Larry R.

1988-01-01

Thin metal sheets are cast by magnetically suspending molten metal deposited within a ferromagnetic yoke and between AC conducting coils and linearly displacing the magnetically levitated liquid metal while it is being cooled to form a solid metal sheet. Magnetic flux increases as the molten metal sheet moves downward and decreases as the molten metal sheet moves upward to stabilize the sheet and maintain it in equilibrium as it is linearly displaced and solidified by cooling gases. A conducting shield is electrically coupled to the molten metal sheet by means of either metal sheet engaging rollers or brushes on the solidified metal, and by means of an electrode in the vessel containing the molten metal thereby providing a return path for the eddy currents induced in the metal sheet by the AC coil generated magnetic flux. Variation in the geometry of the conducting shield allows the magnetic flux between the metal sheet and the conducting shield to be varied and the thickness in surface quality of the metal sheet to be controlled. Side guards provide lateral containment for the molten metal sheet and stabilize and shape the magnetic field while a leader sheet having electromagnetic characteristics similar to those of the metal sheet is used to start the casting process and precedes the molten metal sheet through the magnet and forms a continuous sheet therewith. The magnet may be either U-shaped with a single racetrack coil or may be rectangular with a pair of facing bedstead coils.

Synthesis, structural and electrical properties of [C{sub 2}H{sub 10}N{sub 2}][(SnCl(NCS){sub 2}]{sub 2}

DOE Office of Scientific and Technical Information (OSTI.GOV)

Karoui, Sahel; Kamoun, Slaheddine, E-mail: slah.kamoun@gmail.com; Jouini, Amor

2013-01-15

Synthesis, structural and electrical properties are given for a new organic stannous pseudo halide material. The structure of the [C{sub 2}H{sub 10}N{sub 2}][(SnCl(NCS){sub 2}]{sub 2} reveals that the adjacent Sn(II) centres are bridged by a pair of SCN{sup -} anions to form a 1-D array giving rise to the anionic chains (SnCl(NCS){sub 2}){sub n}{sup n-}. These chains are themselves interconnected by means of N-H Horizontal-Ellipsis Cl(S) hydrogen bonds originating from the organic cation [(NH{sub 3}){sub 2}(CH{sub 2}){sub 2}]{sup 2+}. The AC impedance measurements were performed as a function of both frequency and temperature. The electrical conduction and dielectric relaxation havemore » been studied. The activation energy associated with the electrical relaxation determined from the electric modulus spectra was found close to that of the activation energy obtained for DC conductivity. The conduction mechanisms are attributed to the quantum mechanical tunneling model in phase I and to the proton hopping among hydrogen vacancies in phase II. - Graphical abstract: Atomic coordination in [C2H10N2][SnCl(NCS)2)2]. Highlights: Black-Right-Pointing-Pointer X-ray diffraction analysis shows the 1D network character of the structure. Black-Right-Pointing-Pointer DSC experiments show a phase transition at 336 K. Black-Right-Pointing-Pointer The AC conductivity is interpreted in terms of Jonsher's law. Black-Right-Pointing-Pointer Two conduction mechanisms are proposed for phase I and II.« less

Nonlinear optical conductivity and subharmonic instabilities of graphene in a strong electromagnetic field

NASA Astrophysics Data System (ADS)

Sun, Zhiyuan; Basov, Dimitri; Fogler, Michael

We study theoretically the second-order nonlinear optical conductivity σ (2) of graphene as a function of frequency and momentum. We distinguish two regimes. At frequencies ω higher than the temperature-dependent electron-electron collision rate γee- 1 , the conductivity σ (2) can be derived from the semiclassical kinetic equation. The calculation requires taking into account the photon drag (Lorentz force) due to the ac magnetic field. In the low-frequency hydrodynamic regime ω <<γee- 1 , the nonlinear conductivity has a different form and the photon drag effect is suppressed. As a consequence of the nonlinearity, a strong enough photoexcitation can cause spontaneous generation of collective modes in a graphene strip: plasmons in the high-frequency regime and energy waves (demons) in the hydrodynamic one. The dominant instability occurs at frequency ω / 2 .

[Experimental research and analysis on dielectric properties of blood in anemia mice].

PubMed

Shen, Ben; Liang, Quiyan; Gao, Weiqi; You, Chu; Hong, Mengqi; Ma, Qing

2013-12-01

The conductivity and permittivity of blood in mice were measured by the AC electrical impedance method at frequency range of 0.1-100MHz, and then the changes of the Cole-Cole parameters of dielectric spectra of blood from phenylhydrazine-induced anemia mice were observed by numerical calculation and curve fitting residual analysis of the Cole-Cole equation. The results showed that hematocrit (Hct) of the mice with phenylhydrazine injection was significantly reduced; the permittivity(epsilon) spectroscopy of blood moved to the low insulating region and its permittivity decreased; conductivity (kappa) spectrum curve of blood moved to the high conductivity zone and conductivity increased; the 2nd characteristic frequency was lower than that in the normal group. There was phenylhydrazine dose dependent in the changes of the Cole-Cole parameters of dielectric spectra of blood.

Ionic conductivity of sodium silicate glasses grown within confined volume of mesoporous silica template

NASA Astrophysics Data System (ADS)

Chatterjee, Soumi; Saha, Shyamal Kumar; Chakravorty, Dipankar

2018-04-01

Nanodimensional sodium silicate glasses of composition 30Na2O.70SiO2 has been prepared within the pores of 5.5 nm of mesoporous silica as a template using the surfactant P123. The nanocomposite was characterized by X-ray diffraction, transmission electron microscope, and X-ray photoelectron spectroscopy. Electrical conductivity of the sample was studied by ac impedance spectroscopy. The activation energy for ionic conduction was found to be 0.13 eV with dc conductivity at room temperature of 10-6 S-cm-1. This is attributed to the creation of oxygen ion vacancies at the interface of mesoporous silica and nanoglass arising out of the presence of Si2+ species in the system. These nanocomposites are expected to be useful for applications in sodiumion battery for storage of renewable energy.

Thermal conductivity study of warm dense matter by differential heating on LCLS and Titan

NASA Astrophysics Data System (ADS)

Hill, M.; McKelvey, A.; Jiang, S.; Shepherd, R.; Hau-Riege, S.; Whitley, H.; Sterne, P.; Hamel, S.; Collins, G.; Ping, Y.; Brown, C.; Floyd, E.; Fyrth, J.; Hoarty, D.; Hua, R.; Bailly-Grandvaux, M.; Beg, F.; Cho, B.; Kim, M.; Lee, J.; Lee, H.; Galtier, E.

2017-10-01

A differential heating platform has been developed for thermal conduction study, where a temperature gradient is induced and subsequent heat flow is probed by time-resolved diagnostics. Multiple experiment using this platform have been carried out at LCLS-MEC and Titan laser facilities for warm dense Al, Fe, amorphous carbon and diamond. Two single-shot time-resolved diagnostics are employed, SOP (streaked optical pyrometry) for surface temperature and FDI (Fourier Domain Interferometry) for surface expansion. Both diagnostics provided excellent data to constrain release equation-of-state (EOS) and thermal conductivity. Data sets with varying target thickness and comparison between simulations with different thermal conductivity models are presented. This work was performed under DOE contract DE-AC52-07NA27344 with support from DOE OFES Early Career program and LLNL LDRD program.

[Toluene, Benzene and Acetone Adsorption by Activated Carbon Coated with PDMS].

PubMed

Liu, Han-bing; Jiang, Xin; Wang, Xin; Yang, Bing; Xue, Nan-dong; Zhang, Shi-lei

2016-04-15

To improve the adsorption selectivity of volatile organic compounds ( VOCs) , activated carbon ( AC) was modified by polydimethylsiloxane (PDMS) and characterized by BET analysis and Boehm titration. Dynamic adsorption column experiments were conducted and Yoon-Neslon(Y-N) model was used to identify adsorption effect for toluene, beuzene and acetone on AC when relative humidity was 0%, 50% and 90%, respectively. The results showed that the BET area, micropore volume and surface functional groups decreased with the PDMS modification, and surface hydrophobicity of the modified AC was enhanced leading to a lower water adsorption capacity. The results of dynamic adsorption showed that the adsorption kinetics and capacity of Bare-AC decreased with the increase of relative humidity, and the adsorption capacities of PDMS coated AC were 1.86 times (toluene) and 1.92 times (benzene) higher than those of Bare-AC, while a significant improvement of adsorption capacity for acetone was not observed. These findings suggest that polarity of molecule can be an important influencing factor for adsorption on hydrophobic surface developed by PDMS.

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. Copyright © 2015 Elsevier Inc. All rights reserved.

Electromagnetic environment measurements of PRT systems at "TRANSPO 72" : volume VIII, Dashaveyor System

DOT National Transportation Integrated Search

1999-01-01

The report covers the measurements of the broadband conducted noise present on the A.C. power lines feeding the Personalized Rapid Transit (PRT) systems at Dulles Airport with each system operating individually. The purpose of the measurement effort ...

Electromagnetic Environment Measurements of PRT Systems at "TRANSPO 72" : Volume XI, TTI System

DOT National Transportation Integrated Search

1974-01-01

This report covers the masurements of the broadband conducted noise present on the A.C. power lines feeding the Personalized Rapid Transit (PRT) systems at Dulles Airport with each system operating individually. : The purpose of the measurement effor...

Electromagnetic Environment Measurements of PRT Systems at "TRANSPO 72" : Volume IX, Ford System

DOT National Transportation Integrated Search

1974-01-01

This report covers the masurements of the broadband conducted noise present on the A.C. power lines feeding the Personalized Rapid Transit (PRT) systems at Dulles Airport with each system operating individually. : The purpose of the measurement effor...

Electromagnetic Environment Measurements of PRT Systems at "TRANSPO 72" : Volume XII

DOT National Transportation Integrated Search

1974-01-01

The report covers the measurements of the broadband conducted noise present on the A.C. power lines feeding the Personalized Rapid Transit (PRT) systems with all four systems operating simultaneously. The purpose of the measurement effort was to eval...

Electromagnetic Environment Measurements of PRT Systems at "TRANSPO 72" : Volume X, Monocab System

DOT National Transportation Integrated Search

1974-01-01

The report covers the measurements of the broadband conducted noise present on the A.C. power lines feeding the Personalized Rapid Transit (PRT) systems at Dulles Airport with each system operating individually. The purpose of the measurement effort ...

VIRTUAL SYMPOSIUM: STATE OF THE SCIENCE--PPCPS AS ENVIRONMENTAL POLLUTANTS

EPA Science Inventory

This document provides a brief summary of how this pioneering meeting for the ACS was conducted, as well as some perspective and insights that could prove useful for those who might beinterested in organizing and hosting their own "virtual" meeting.

Effect of Chelating Agents on the Stability of Nano-TiO2 Sol Particles for Sol-Gel Coating.

PubMed

Maeng, Wan Young; Yoo, Mi

2015-11-01

Agglomeration of sol particles in a titanium alkoxide (tetrabutyl orthotitanate (TBOT), > 97%) solution during the hydrolysis and condensation steps makes the sol solution difficult to use for synthesizing homogeneous sol-gel coating. Here, we have investigated the effect of stabilizing agents (acetic acid and ethyl acetoacetate (EAcAc)) on the agglomeration of Ti alkoxide particles during hydrolysis and condensation in order to determine the optimized conditions for controlling the precipitation of TiO2 particles. The study was conducted at R(AC) ([acetic acid]/[TBOT]) = 0.1-5 and R(EAcAc)([EAcAc]/[TBOT]) = 0.05-0.65. We also studied the effects of a basic catalyst ethanolamine (ETA), water, and HCl on sol stability. The chelating ligands in the precursor sol were analyzed with FT-IR. The coating properties were examined by focused ion beam. The stabilizing agents (acetic acid and EAcAc) significantly influenced the agglomeration and precipitation of TBOT precursor particles during hydrolysis. As R(AC) and R(EAcAc) increased, the agglomeration remarkably decreased. The stability of the sol with acetic acid and EAcAc arises from the coordination of the chelating ligand to TBOT that hinders hydrolysis and condensation. A uniform fine coating (thickness: 30 nm) on stainless steel was obtained by using an optimized sol with R(AC) = 0.5 and R(EAcAc) = 0.65.

EPG waveform library for Graphocephala atropunctata (Hemiptera: Cicadellidae): Effect of adhesive, input resistor, and voltage levels on waveform appearance and stylet probing behaviors.

PubMed

Cervantes, Felix A; Backus, Elaine A

2018-05-31

Blue-green sharpshooter, Graphocephala atropunctata, is a native California vector of Xylella fastidiosa (Xf), a foregut-borne bacterium that is the causal agent of Pierce's disease in grapevines. A 3rd-generation, AC-DC electropenetrograph (EPG monitor) was used to record stylet probing and ingestion behaviors of adult G. atropunctata on healthy grapevines. This study presents for the first time a complete, updated waveform library for this species, as well as effects of different electropenetrograph settings and adhesives on waveform appearances. Both AC and DC applied signals were used with input resistor (Ri) levels (amplifier sensitivities) of 10 6 , 10 7 , 10 8 and 10 9  Ohms, as well as two type of adhesives, conducting silver paint and handmade silver glue. Waveform description, characterization of electrical origins (R versus emf components), and proposed biological meanings of waveforms are reported, as well as qualitative differences in waveform appearances observed with different electropenetrograph settings and adhesives. In addition, a quantitative study with AC signal, using two applied voltage levels (50 and 200 mV) and two Ri levels (10 7 and 10 9  Ohms) was performed. Intermediate Ri levels 10 7 and 10 8  Ohms provided EPG waveforms with the greatest amount of information, because both levels captured similar proportions of R and emf components, as supported by appearance, clarity, and definition of waveforms. Similarly, use of a gold wire loop plus handmade silver glue provided more definition of waveforms than a gold wire loop plus commercial conducting silver paint. Qualitative/observational evidence suggested that AC applied signal caused fewer aberrant behaviors/waveforms than DC applied signal. In the quantitative study, behavioral components of the sharpshooter X wave were the most affected by changes in Ri and voltage level. Because the X wave probably represents X. fastidiosa inoculation behavior, future studies of X. fastidiosa inoculation via EPG will require carefully determined instrument settings. An intermediate Ri level such as 10 8  Ohms with low voltage, AC applied signal, and gold wire loop plus silver glue is recommended as the best electropenetrograph methods to conduct future EPG studies of sharpshooter inoculation behaviors on Xf-resistant and -susceptible grapevine. Copyright © 2018. Published by Elsevier Ltd.

Preliminary design of a Primary Loop Pump Assembly (PLPA), using electromagnetic pumps

NASA Technical Reports Server (NTRS)

Moss, T. A.; Matlin, G.; Donelan, L.; Johnson, J. L.; Rowe, I.

1972-01-01

A preliminary design study of flight-type dc conduction-permanent magnetic, ac helical induction, and ac linear induction pumps for circulating 883 K (1130 F) NaK at 9.1 kg/sec (20 lb/sec) is described. Various electromagnetic pump geometrics are evaluated against hydraulic performance, and the effects of multiple windings and numbers of pumps per assembly on overall reliability were determined. The methods used in the electrical-hydraulic, stress, and thermal analysis are discussed, and the high temperature electrical materials selected for the application are listed.

Environmental Fate Model for Ultra-Low-Volume Insecticide Applications Used for Adult Mosquito Management

DTIC Science & Technology

2012-01-01

h. Applica- tions occurred when the prevailing wind was blowing perpendicular to the collection site (Fig. 1). Sprays were conducted using a Guardian...min. Permanone 30–30 was mixed 1:2:1 with Crystal Plus 70 T light mineral oil (STE Oil Company, Inc., San Marcos, TX, USA) and ACS grade toluene and...applied at a flow rate of 192 ml/min. Scourge 18+54wasmixed at 1:0.4:0.4with Crystal Plus 70 T light mineral oil and ACS grade toluene and applied at a

Selective and Efficient Generation of ortho-Brominated para-Substituted Phenols in ACS-Grade Methanol.

PubMed

Georgiev, David; Saes, Bartholomeus W H; Johnston, Heather J; Boys, Sarah K; Healy, Alan; Hulme, Alison N

2016-01-13

The mono ortho-bromination of phenolic building blocks by NBS has been achieved in short reaction times (15-20 min) using ACS-grade methanol as a solvent. The reactions can be conducted on phenol, naphthol and biphenol substrates, giving yields of >86% on gram scale. Excellent selectivity for the desired mono ortho-brominated products is achieved in the presence of 10 mol % para-TsOH, and the reaction is shown to be tolerant of a range of substituents, including CH3, F, and NHBoc.

Working Towards Net Zero Energy at Fort Irwin, CA

DTIC Science & Technology

2010-09-01

capacity factor for the solar photovoltaic analysis was based on simu- lations conducted by National Renewable Energy Laboratory (NREL) for Las Vegas, NV...kWhAC/kWhDC) x 8760 hrs = 5240 kWhAC/yr Savings for annual electricity savings are: 5240 kWh x 8.3 cents/kWh = $435/yr The capacity factor for the...43,668 kWh/yr Annual electricity savings are: 43,668 kWh x 8.3 cents/kWh = $3624/yr The capacity factor for the solar photovoltaic analysis was

AC Electroosmotic Pumping in Nanofluidic Funnels.

PubMed

Kneller, Andrew R; Haywood, Daniel G; Jacobson, Stephen C

2016-06-21

We report efficient pumping of fluids through nanofluidic funnels when a symmetric AC waveform is applied. The asymmetric geometry of the nanofluidic funnel induces not only ion current rectification but also electroosmotic flow rectification. In the base-to-tip direction, the funnel exhibits a lower ion conductance and a higher electroosmotic flow velocity, whereas, in the tip-to-base direction, the funnel has a higher ion conductance and a lower electroosmotic flow velocity. Consequently, symmetric AC waveforms easily pump fluid through the nanofunnels over a range of frequencies, e.g., 5 Hz to 5 kHz. In our experiments, the nanofunnels were milled into glass substrates with a focused ion beam (FIB) instrument, and the funnel design had a constant 5° taper with aspect ratios (funnel tip width to funnel depth) of 0.1 to 1.0. We tracked ion current rectification by current-voltage (I-V) response and electroosmotic flow rectification by transport of a zwitterionic fluorescent probe. Rectification of ion current and electroosmotic flow increased with increasing electric field applied to the nanofunnel. Our results support three-dimensional simulations of ion transport and electroosmotic transport through nanofunnels, which suggest the asymmetric electroosmotic transport stems from an induced pressure at the junction of the nanochannel and nanofunnel tip.

Three-Dimensionally Hierarchical Graphene Based Aerogel Encapsulated Sulfur as Cathode for Lithium/Sulfur Batteries

PubMed Central

Li, Haipeng; Sun, Liancheng; Wang, Zhuo; Zhang, Yongguang; Tan, Taizhe; Wang, Gongkai

2018-01-01

A simple and effective method was developed to obtain the electrode for lithium/sulfur (Li/S) batteries with high specific capacity and cycling durability via adopting an interconnected sulfur/activated carbon/graphene (reduced graphene oxide) aerogel (S/AC/GA) cathode architecture. The AC/GA composite with a well-defined interconnected conductive network was prepared by a reduction-induced self-assembly process, which allows for obtaining compact and porous structures. During this process, reduced graphene oxide (RGO) was formed, and due to the presence of oxygen-containing functional groups on its surface, it not only improves the electronic conductivity of the cathode but also effectively inhibits the polysulfides dissolution and shuttle. The introduced activated carbon allowed for lateral and vertical connection between individual graphene sheets, completing the formation of a stable three-dimensionally (3D) interconnected graphene framework. Moreover, a high specific surface area and 3D interconnected porous structure efficiently hosts a higher amount of active sulfur material, about 65 wt %. The designed S/AC/GA composite electrodes deliver an initial capacity of 1159 mAh g−1 at 0.1 C and can retain a capacity of 765 mAh g−1 after 100 cycles in potential range from 1 V to 3 V. PMID:29373525

Structural and electrical characterisation of Li(2)O : TiO(2) : SnO(2) : P(2)O(5) electrolyte glass.

PubMed

Abrahams, Isaac; Hadzifejzovic, Emina; Dygas, Jozef R

2004-10-07

Glasses of general formula 50Li(2)O : xSnO(2) : (10 -x)TiO(2) : 40P(2)O(5)(0.0 < or = x < or = 10) were investigated by differential scanning calorimetry, X-ray diffraction and ac impedance, (31)P solid-state NMR and IR spectroscopies. Three isotropic resonances can be identified in the (31)P NMR spectra, which have been assigned to various phosphate species. Analysis of the ratios of integrated intensities in the (31)P spectra leads to models for the Ti and Sn coordination environments. Both TiO(2) and SnO(2) are found to be predominantly network forming with Ti and Sn proposed to be in five- and four-coordinate environments respectively. Analysis of ac impedance spectra collected at low temperatures reveals two forms of permittivity dispersion, viz: high frequency conductivity dispersion and Cole-Cole type relaxation of permittivity. The activation energy of the relaxation frequency of the permittivity dispersion is equal to that of the dc conductivity, which is consistent with cooperative motion of lithium ions. The results also suggest that the observed increase in conductivity with temperature appears to be mainly due to an increase in mobility rather than increase in carrier concentration.

Dielectric properties of Ti4+ substituted BaFe12O19 nanoparticles

NASA Astrophysics Data System (ADS)

Ghoneim, A. I.; Amer, M. A.; Meaz, T. M.; Attalah, S. S.

2017-02-01

Series of nanocrystalline BaTixFe12-(4/3)xO19 hexagonal ferrites, 0≤x≤1, was prepared using the chemical co-precipitation method. As-prepared samples were heated at 1200 °C for 20 h and slowly cooled to room temperature (RT). XRD studies proved that the samples have single phase M-type hexagonal nanostructure, where their grain size lies in the range of 42.4 - 61.3 nm. Their dielectric properties were studied against temperature (T) and frequency (F). DC conductivity showed increase against T, whereas AC conductivity showed increase with increasing both T and F. This proved the semiconducting behavior of the samples. Activation energies were found to lie in the range of 0.054-0.169 eV for temperature range of RT 373 K and of 0.114-0.274 eV for higher temperatures up to 473 K. Variation of the dielectric constant and AC conductivity against F revealed dispersion in all these hexagonal nanostructures, which was assigned to Maxwell-Wagner type of interfacial polarization. Variation of the dielectric loss tangent against F showed a relaxation spectrum for all samples, whereas the dielectric constant and loss tangent showed an increasing trend against T. The relative magnetic permeability μr showed an increasing trend with temperature.

Fluid volume displacement at the oval and round windows with air and bone conduction stimulation.

PubMed

Stenfelt, Stefan; Hato, Naohito; Goode, Richard L

2004-02-01

The fluids in the cochlea are normally considered incompressible, and the fluid volume displacement of the oval window (OW) and the round window (RW) should be equal and of opposite phase. However, other channels, such as the cochlear and vestibular aqueducts, may affect the fluid flow. To test if the OW and RW fluid flows are equal and of opposite phase, the volume displacement was assessed by multiple point measurement at the windows with a laser Doppler vibrometer. This was done during air conduction (AC) stimulation in seven fresh human temporal bones, and with bone conduction (BC) stimulation in eight temporal bones and one human cadaver head. With AC stimulation, the average volume displacement of the two windows is within 3 dB, and the phase difference is close to 180 degrees for the frequency range 0.1 to 10 kHz. With BC stimulation, the average volume displacement difference between the two windows is greater: below 2 kHz, the volume displacement at the RW is 5 to 15 dB greater than at the OW and above 2 kHz more fluid is displaced at the OW. With BC stimulation, lesions at the OW caused only minor changes of the fluid flow at the RW.

Fluid volume displacement at the oval and round windows with air and bone conduction stimulation

NASA Astrophysics Data System (ADS)

Stenfelt, Stefan; Hato, Naohito; Goode, Richard L.

2004-02-01

The fluids in the cochlea are normally considered incompressible, and the fluid volume displacement of the oval window (OW) and the round window (RW) should be equal and of opposite phase. However, other channels, such as the cochlear and vestibular aqueducts, may affect the fluid flow. To test if the OW and RW fluid flows are equal and of opposite phase, the volume displacement was assessed by multiple point measurement at the windows with a laser Doppler vibrometer. This was done during air conduction (AC) stimulation in seven fresh human temporal bones, and with bone conduction (BC) stimulation in eight temporal bones and one human cadaver head. With AC stimulation, the average volume displacement of the two windows is within 3 dB, and the phase difference is close to 180° for the frequency range 0.1 to 10 kHz. With BC stimulation, the average volume displacement difference between the two windows is greater: below 2 kHz, the volume displacement at the RW is 5 to 15 dB greater than at the OW and above 2 kHz more fluid is displaced at the OW. With BC stimulation, lesions at the OW caused only minor changes of the fluid flow at the RW.

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

NASA Astrophysics Data System (ADS)

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

2017-04-01

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

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.

AC electroosmotic micromixer for chemical processing in a microchannel.

PubMed

Sasaki, Naoki; Kitamori, Takehiko; Kim, Haeng-Boo

2006-04-01

A rapid micromixer of fluids in a microchannel is presented. The mixer uses AC electroosmotic flow, which is induced by applying an AC voltage to a pair of coplanar meandering electrodes configured in parallel to the channel. To demonstrate performance of the mixer, dilution experiments were conducted using a dye solution in a channel of 120 microm width. Rapid mixing was observed for flow velocity up to 12 mm s(-1). The mixing time was 0.18 s, which was 20-fold faster than that of diffusional mixing without an additional mixing mechanism. Compared with the performance of reported micromixers, the present mixer worked with a shorter mixing length, particularly at low Peclet numbers (Pe < 2 x 10(3)).

A new infusion pathway monitoring system utilizing electrostatic induced potential.

PubMed

Maki, Hiromichi; Yonezawa, Yoshiharu; Ogawa, Hidekuni; Ninomiya, Ishio; Sada, Kouji; Hamada, Shingo; Hahn, Alien W; Caldwell, W Morton

2006-01-01

We have developed a new infusion pathway monitoring system employing linear integrated circuits and a low-power 8-bit single chip microcomputer. The system is available for hospital and home use and it constantly monitors the intactness of the pathway. The sensor is an electro-conductive polymer electrode wrapped around the infusion polyvinyl chloride infusion tube. This records an AC (alternating current) voltage induced on the patient's body by electrostatic coupling from the normal 100 volt, 60 Hz AC power line wiring field in the patient's room. If the injection needle or infusion tube becomes detached, then the system detects changes in the induced AC voltage and alerts the nursing station, via the nurse call system or PHS (personal handy phone System).

A new venous infusion pathway monitoring system.

PubMed

Maki, Hiromichi; Yonezawa, Yoshiharu; Ogawa, Hidekuni; Ninomiya, Ishio; Sata, Koji; Hamada, Shingo; Caldwell, W Morton

2007-01-01

A new infusion catheter pathway monitoring system employing linear integrated circuits and a low-power 8-bit single chip microcomputer has been developed for hospital and home use. The sensor consists of coaxial three-layer conductive tapes wrapped around the polyvinyl chloride infusion tube. The inner tape is the main electrode, which records an AC (alternating current) voltage induced on the patient's body by electrostatic coupling from the normal 100 volt, 60 Hz AC power line wiring field in the patient's room. The outside tape layer is a reference electrode to monitor the AC voltage around the main electrode. The center tape layer is connected to system ground and functions as a shield. The microcomputer calculates the ratio of the induced AC voltages recorded by the main and reference electrodes and if the ratio indicates a detached infusion, alerts the nursing station, via the nurse call system or low transmitting power mobile phone.

A critical comparison of electrical methods for measuring spin-orbit torques

NASA Astrophysics Data System (ADS)

Zhang, Xuanzi; Hung, Yu-Ming; Rehm, Laura; Kent, Andrew D.

Direct (DC) and alternating current (AC) transport measurements of spin-orbit torques (SOTs) in heavy metal-ferromagnet heterostructure with perpendicular magnetic anisotropy have been proposed and demonstrated. A DC method measures the change of perpendicular magnetization component while an AC method probes the first and second harmonic magnetization oscillation in responses to an AC current (~1 kHz). Here we conduct both types of measurements on β-Ta/CoFeB/MgO in the form of patterned Hall bars (20 μm linewidth) and compare the results. Experiments results are qualitatively in agreement with a macro spin model including Slonzewski-like and a field-like SOTs. However, the effective field from the ac method is larger than that obtained from the DC method. We discuss the possible origins of the discrepancy and its implications for quantitatively determining SOTs. Research supported by the SRC-INDEX program, NSF-DMR-1309202 and NYU-DURF award.

Superfund record of decision (EPA Region 9): Aircraft Control and Warning Site, Mather Air Force Base, CA, December 1993

DOE Office of Scientific and Technical Information (OSTI.GOV)

Not Available

This decision document, a Record of Decision (ROD), presents the selected remedial action for the AC W Site, Installation Restoration Program (IRP) Site 12, at Mather Air Force Base (AFB), Sacramento County, California. Reports indicate that from 1958 to 1966 waste solvents and transformer oils were disposed in a waste disposal pipe in the AC W area. Investigations conducted as part of the Air Force Installation Restoration Program (IRP) failed to locate the waste disposal pipe but did find trichloroethylene (TCE) contamination in the shallow water bearing zone (SWBZ) in the AC W area. The SWBZ is classified as amore » potential source of drinking water by the State of California, although it is not currently used in the AC W area. The selected remedy will address the potential threat to human health posed by TCE contamination in groundwater (primarily in the SWBZ).« less

Magnetic sorbents added to soil slurries lower Cr aqueous concentration

NASA Astrophysics Data System (ADS)

Aravantinos, Konstantinos; Isari, Ekavi; Karapanagioti, Hrissi K.; Manariotis, Ioannis D.; Werner, David

2016-04-01

Activated carbon (AC) acts as a strong binding agent that lowers the pollutant concentration and, thus its toxicity. Another promising sorbent material in environmental applications is biochar (BC) which is obtained from the incomplete combustion of carbon-rich biomass under oxygen-limited conditions. Both of these materials could be used as soil or sediment amendments that would lower the toxicity in the aqueous phase. A draw back of this technique is that although the pollutant will remain non- bioavailable for many years being sorbed into these sorbents, it actually stays into the system. The objective of this study was (a) to synthesize a magnetic powdered activated carbon (AC/Fe) and magnetic powdered biochar (BC/Fe) produced from a commercial AC sample and BC, respectively and (b) to evaluate the potential use of AC/Fe and BC/Fe to lower Cr concentration that desorb from two soils in their soil slurries. The two soil samples originate from the vicinity of a local metal shop. The BC was produced from olive pomace. The surface area, the pore volume, and the average pore size of each sorbent were determined using gas (N2) adsorption-desorption cycles and the Brunauer, Emmett, and Teller (BET) equation. Isotherms with 30 adsorption and 20 desorption points were conducted at liquid nitrogen temperature (77K). Open surface area and micropore volume were determined using t-plot method and Harkins & Jura equation. For both AC/Fe, surface area measurements resulted in 66% those of corresponding AC. For BC/Fe, the surface area was 82% that of BC. Our previous studies have shown that both AC/Fe and BC/Fe are effective sorbents for mercury in aqueous solutions but with lower sorption capacity compared to the initial materials (50-75% lower). Batch experiments with all sorbent samples and each soil were conducted at room temperature (25oC) in order to compare the sorption properties of the materials. The soil slurries demonstrated low Cr concentrations (10.9 and 14.6 μg/L, respectively). One month after the addition of amendments AC, AC/Fe, and BC/Fe, Cr concentration in the slurry was lower than the detection limit which was 0.5 μg/L (except of one of the soils with the AC that was 2.1 μg/L). The slurries with BC demonstrated Cr concentrations equal to 4.2 and 7.1 μg/L, respectively. All these properties point to promising materials that can effectively be used for in-situ environmental remediation and also be recovered.

Obtaining continuous BrAC/BAC estimates in the field: A hybrid system integrating transdermal alcohol biosensor, Intellidrink smartphone app, and BrAC Estimator software tools.

PubMed

Luczak, Susan E; Hawkins, Ashley L; Dai, Zheng; Wichmann, Raphael; Wang, Chunming; Rosen, I Gary

2018-08-01

Biosensors have been developed to measure transdermal alcohol concentration (TAC), but converting TAC into interpretable indices of blood/breath alcohol concentration (BAC/BrAC) is difficult because of variations that occur in TAC across individuals, drinking episodes, and devices. We have developed mathematical models and the BrAC Estimator software for calibrating and inverting TAC into quantifiable BrAC estimates (eBrAC). The calibration protocol to determine the individualized parameters for a specific individual wearing a specific device requires a drinking session in which BrAC and TAC measurements are obtained simultaneously. This calibration protocol was originally conducted in the laboratory with breath analyzers used to produce the BrAC data. Here we develop and test an alternative calibration protocol using drinking diary data collected in the field with the smartphone app Intellidrink to produce the BrAC calibration data. We compared BrAC Estimator software results for 11 drinking episodes collected by an expert user when using Intellidrink versus breath analyzer measurements as BrAC calibration data. Inversion phase results indicated the Intellidrink calibration protocol produced similar eBrAC curves and captured peak eBrAC to within 0.0003%, time of peak eBrAC to within 18min, and area under the eBrAC curve to within 0.025% alcohol-hours as the breath analyzer calibration protocol. This study provides evidence that drinking diary data can be used in place of breath analyzer data in the BrAC Estimator software calibration procedure, which can reduce participant and researcher burden and expand the potential software user pool beyond researchers studying participants who can drink in the laboratory. Copyright © 2017. Published by Elsevier Ltd.

An Examination of Workplace Influences on Active Commuting in a Sample of University Employees.

PubMed

Bopp, Melissa; Sims, Dangaia; Colgan, Joanna; Rovniak, Liza; Matthews, Stephen A; Poole, Erika

2016-01-01

Active commuting (AC; walking or biking) to work is associated with many benefits, though rates remain low. Employers can benefit from greater employee AC, through improved employee physical activity, though how the workplace is related to AC is unclear. The current study sought to examine how the workplace environment is related to AC participation. This was a cross-sectional, online survey conducted in April-May 2014. A volunteer sample of university employees (n = 551) was recruited. A large university in the northeastern United States. The online survey addressed travel habits, demographics, and workplace social and physical environment for AC. Pearson correlations and t tests were used to examine relationships between the percentage of all trips as AC and workplace influences and a multivariate regression analysis predicted AC participation. Participants reported 0.86 ± 2.6 AC trips per week. Percentage of trips as AC trips associated with perceived coworker AC (P < .001), parking availability (r = -0.22, P < .001), and bike parking availability (r = 0.24, P < .001). Individuals reporting greater walking time from their parking spot to their workplace reported a higher percentage of trips as AC compared with those with closer parking (P < .001). Individuals with a parking pass were less likely to AC than those with no permit (P < .001). The full multivariate model explained 42.5% of the variance in percentage of trips per week via AC (P < .001), having a parking pass (B = 0.23, P < .001), parking availability (B = -0.17, P < .001), perceived coworkers AC (B = 0.08, P = .02), and greater perceived walk time to campus (B = -0.43, P < .001) as significant predictors. This study provided insight into institutional influences on AC, indicating that policy, infrastructure, and programmatic initiatives could be used to promote workplace AC.

Effect of polyvinylpyrrolidone content on alternating current conductivity of polyaniline

NASA Astrophysics Data System (ADS)

Megha, R.; Kumar, T. G. Naveen; Ravikiran, Y. T.; Prakash, H. G. Raj; Revanasiddappa, M.; Kumari, S. C. Vijaya

2018-05-01

In the present work, Polyaniline (PANI) and Polyaniline-polyvinylpyrrolidone (PANI-PVP) composites of two different weight percentages of PVP were synthesized separately by simple chemical polymerization method. The interaction between PANI and PVP in each of the composite was confirmed by Attenuated total reflection infrared spectroscopic (AT-IR) technique. The alternate current (AC) response characteristics at room temperature of PANI and the composites in the frequency range 50 Hz-1 MHz were comparatively studied. Both the composites have shown decreased conductivity as compared to that of PANI.

Characterization of anisotropic thermal conductivity of suspended nm-thick black phosphorus with frequency-resolved Raman spectroscopy

NASA Astrophysics Data System (ADS)

Wang, Tianyu; Han, Meng; Wang, Ridong; Yuan, Pengyu; Xu, Shen; Wang, Xinwei

2018-04-01

Frequency-resolved Raman spectroscopy (FR-Raman) is a new technique for nondestructive thermal characterization. Here, we apply this new technique to measure the anisotropic thermal conductivity of suspended nm-thick black phosphorus samples without the need of optical absorption and temperature coefficient. Four samples with thicknesses between 99.8 and 157.6 nm are studied. Based on steady state laser heating and Raman measurement of samples with a specifically designed thermal transport path, the thermal conductivity ratio (κZZ/κAC) is determined to be 1.86-3.06. Based on the FR-Raman measurements, the armchair thermal conductivity is measured as 14-22 W m-1 K-1, while the zigzag thermal conductivity is 40-63 W m-1 K-1. FR-Raman has great potential for studying the thermal properties of various nanomaterials. This study significantly advances our understanding of thermal transport in black phosphorus and facilitates the application of black phosphorus in novel devices.

Electrical conductivity and dielectric behavior in sodium zinc divanadates

NASA Astrophysics Data System (ADS)

Sallemi, F.; Louati, B.; Guidara, K.

2014-11-01

The Na2ZnV2O7 compound was obtained by the conventional solid-state reaction. The sample was characterized by X-ray powder diffraction, Raman and impedance spectroscopy. The ac electrical conductivity and dielectric properties have been investigated in the frequency and temperature range of 200 Hz-1 MHz and 513 K-729 K, respectively. The direct current conductivity process is thermally activated. The frequency dependence of the conductivity is interpreted using the power law. The close values of activation energies obtained from the analysis of hopping frequency and dc conductivity implies that the transport is due to Na+ cation displacement parallel to (0 0 1) plane located between ZnO4 and VO4 tetrahedra. The evolution of the complex permittivity as a function of angular frequency was investigated. Several important parameters such as charge carrier concentration, ionic mobility and diffusion coefficient were determined. Thermodynamic parameters such as the free energy of activation ∆F, the enthalpy ∆H, and the change in entropy ∆S have been calculated.

Self-supporting activated carbon/carbon nanotube/reduced graphene oxide flexible electrode for high performance supercapacitor

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Xing; Tang, Yao; Song, Junhua

A self-supporting and flexible activated carbon/carbon nanotube/reduced graphene oxide (AC/CNT/RGO) film has been rationally designed for constructing high- performance supercapacitor. The AC/CNT/RGO film is prepared by anchoring the AC particles with a 3D and porous framework built by hierarchically weaving the 1 D CNT and 2D RGO using their intrinsic van der Waals force. The CNT network is beneficial for improving the electronic conductivity of the electrode, while the AC particles could effectively suppress the aggregation of RGO and CNT due to their blocking effect. The synergistic effects among the AC, CNT and RGO validate the AC/CNT/RGO as a promisingmore » electrode for supercapacitor, exhibiting greatly enhanced electrochemical performances in comparison with the pure RGO film, pure CNT film and AC electrode. The AC/CNT/RGO electrode delivers a high specific capacitance of 101 F g-1 at the current density of 0.2 A g-1, offering a maximum energy density of 30.0 W h kg-1 in organic electrolyte at the cut-off voltage range of 0.001~3.0 V. The findings of this work open a new avenue for the design of self-supporting electrodes for the development of flexible and light weight energy storage supercapacitor.« less

Conductive cable fibers with insulating surface prepared by co-axial electrospinning of multi-walled nanotubes and cellulose

PubMed Central

Miyauchi, Minoru; Miao, Jianjun; Simmons, Trevor J.; Lee, Jong-Won; Doherty, Thomas V.; Dordick, Jonathan S.; Linhardt, Robert J.

2010-01-01

A core-sheath of multi-walled carbon nanotube (MWNT)-cellulose fibers of diameters from several hundreds nm to several µm were prepared by co-axial electrospinning from a non-valatile, non-flammable ionic liquid (IL) solvent, 1-methyl-3-methylimidazolium acetate ([EMIM][Ac]). MWNTs were dispersed in IL to form a gel solution. This gel core solution was electrospun surrounded by a sheath solution of cellulose disolved in the same IL. Electrospun fibers were collected in a coagulation bath containing ethanol-water to completely remove the IL and dried to form a core-sheath MWNT-cellulose fibers having a cable structure with a conductive core and insulating sheath. Enzymatic treatment of a portion of a mat of these fibers with cellulase selectively removed the cellulose sheath exposing the MWNT core for connection to an electrode. These MWNT-cellulose fiber mats demonstrated excellent conductivity due to a conductive pathway of bundleled MWNTs. Fiber mat conductivity increased with increasing ratio of MWNT in the fibers with a maximum conductivity of 10.7 S/m obtained at 45 wt% MWNT loading. PMID:20690644

Conductive cable fibers with insulating surface prepared by coaxial electrospinning of multiwalled nanotubes and cellulose.

PubMed

Miyauchi, Minoru; Miao, Jianjun; Simmons, Trevor J; Lee, Jong-Won; Doherty, Thomas V; Dordick, Jonathan S; Linhardt, Robert J

2010-09-13

Core-sheath multiwalled carbon nanotube (MWNT)-cellulose fibers of diameters from several hundreds of nanometers to several micrometers were prepared by coaxial electrospinning from a nonvolatile, nonflammable ionic liquid (IL) solvent, 1-methyl-3-methylimidazolium acetate ([EMIM][Ac]). MWNTs were dispersed in IL to form a gel solution. This gel core solution was electrospun surrounded by a sheath solution of cellulose dissolved in the same IL. Electrospun fibers were collected in a coagulation bath containing ethanol-water to remove the IL completely and dried to form core-sheath MWNT-cellulose fibers having a cable structure with a conductive core and insulating sheath. Enzymatic treatment of a portion of a mat of these fibers with cellulase selectively removed the cellulose sheath exposing the MWNT core for connection to an electrode. These MWNT-cellulose fiber mats demonstrated excellent conductivity because of a conductive pathway of bundled MWNTs. Fiber mat conductivity increased with increasing ratio of MWNT in the fibers with a maximum conductivity of 10.7 S/m obtained at 45 wt % MWNT loading.

Development of mix design procedures for gap-graded asphalt-rubber asphalt concrete

DOT National Transportation Integrated Search

2007-11-01

A research project was conducted to identify and document current modifications to ARIZONA 815c (75-blow Marshall method) used to develop gap-graded asphalt rubber asphalt concrete (GG AR AC) mix designs, and to develop and test improvements to provi...

Electromagnetic environment measurements of PRT systems at "TRANSPO 72" : volume VII

DOT National Transportation Integrated Search

1974-01-01

The report covers the measurements of the broadband conducted noise present on the A.C. power lines feeding the Personalized Rapid Transit (PRT) systems at Dulles Airport with all four systems off. The purpose of the measurement effort was to evaluat...

Historical Development of Asphalt Content Determination by the Ignition Method

DOT National Transportation Integrated Search

1996-01-01

This study was conducted to develop a reliable, detailed test procedure for determining asphalt cement (AC) content by the ignition method. The goal was to minimize the overall test time as well as technician time, and to produce a test method with a...

The electrical conductivities of polyimide and polyimide/Li triflate composites: An a.c. impedance study

NASA Astrophysics Data System (ADS)

Aziz, Nor Diyana Abdul; Kamarulzaman, Norlida; Subban, Ri Hanum Yahaya; Hamzah, Ahmad Sazali; Ahmed, Azni Zain; Osman, Zurina; Rusdi, Roshidah; Kamarudin, Norashikin; Mohalid, Norhanim; Romli, Ahmad Zafir; Shaameri, Zurina

2017-09-01

Polymer electrolytes have been an essential area of research for many decades. One of the reasons was the need to find new electrolyte materials suitable for device applications like solid-state batteries, supercapacitors, fuel cells, etc. with enhanced characteristics. For more than 40 years, polyimide has been known as a super-engineering plastic due to its excellent thermal stability (Tg > 250 °C) and mechanical properties. Therefore, in an effort to develop new polymer electrolytes, polyimide as a polymer matrix was chosen. Composite films of the polymer doped with lithium salt, LiCF3SO3 was prepared. These PI based polymer electrolyte films were investigated by the alternating current (a.c.) impedance spectroscopy method in the temperature range from 300 K to 373 K. It was observed that conductivity increased with the increase of temperature and amount of doping salt. Alternatively, the activation energy (Ea) of the composite films decreased with the increase of the doping salt, LiCF3SO3.

Dielectric and structural properties of diffuse ferroelectric phase transition in Pb1.85K1.15Li0.15Nb5O15 ceramic

NASA Astrophysics Data System (ADS)

Choukri, E.; Gagou, Y.; Mezzane, D.; Abkhar, Z.; El Moznine, R.; Luk'yanchuk, I.; Saint-Grégoire, P.; Kavokin, A. V.

2011-02-01

We studied the structural and dielectric properties of new Tetragonal Tungsten Bronze (TTB) ceramics Pb1.85K1.15Li0.15Nb5O15 that was synthesized by solid-state reaction. We pay a special attention to the diffuse phase transition (DPT) that occurs close to 425 °C. Using dielectric measurements in a frequency range of 10 Hz-1 MHz and in the temperature range 30-560 °C, we have shown that the real permittivity close to DPT is well described by Santos-Eiras phenomenological model. Space-charge polarization, relaxation phenomena and free charges conductivity have been analyzed using dielectric spectroscopy impedance and modulus characterization. Cole-Cole plots show a non-Debye (polydispersive) type relaxation. In paraelectric phase the Arrhenius activation energy was determined as Eτ = 0.72 eV. We demonstrated that frequency dependence of ac conductivity at different temperatures obeys the Jonscher's universal law: σac = σdc + A(ω)n.

Lower-Order Compensation Chain Threshold-Reduction Technique for Multi-Stage Voltage Multipliers.

PubMed

Dell' Anna, Francesco; Dong, Tao; Li, Ping; Wen, Yumei; Azadmehr, Mehdi; Casu, Mario; Berg, Yngvar

2018-04-17

This paper presents a novel threshold-compensation technique for multi-stage voltage multipliers employed in low power applications such as passive and autonomous wireless sensing nodes (WSNs) powered by energy harvesters. The proposed threshold-reduction technique enables a topological design methodology which, through an optimum control of the trade-off among transistor conductivity and leakage losses, is aimed at maximizing the voltage conversion efficiency (VCE) for a given ac input signal and physical chip area occupation. The conducted simulations positively assert the validity of the proposed design methodology, emphasizing the exploitable design space yielded by the transistor connection scheme in the voltage multiplier chain. An experimental validation and comparison of threshold-compensation techniques was performed, adopting 2N5247 N-channel junction field effect transistors (JFETs) for the realization of the voltage multiplier prototypes. The attained measurements clearly support the effectiveness of the proposed threshold-reduction approach, which can significantly reduce the chip area occupation for a given target output performance and ac input signal.

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.

Fabrication of PbFe12O19 nanoparticles and study of their structural, magnetic and dielectric properties

NASA Astrophysics Data System (ADS)

Mousavi Ghahfarokhi, S. E.; Rostami, Z. A.; Kazeminezhad, I.

2016-02-01

In this study, M-type Lead hexaferrite (PbFe12O19) nanoparticles were prepared by a sol-gel method and the prepared powders were annealed at 700-1000 °C for 1, 1.5, 2, 2.5 and 3 h. The Lead hexaferrite powders were characterized using thermogravimetry-differential thermal analysis, X-ray diffraction, scanning electron microscopy, LCR meter, vibrating sample magnetometer, and Fourier transforms infrared spectroscopy. The size of the nanoparticles was increased with the annealing temparature. The results reveal that the best annealing temperature and annealing time for preparing PbFe12O19 nanoparticles at 800 °C and 3 h are obtained. The infrared spectra measured in range of 4000-400 cm-1 exhibit stretching modes of metal ions in tetrahedral site at 580-550 cm-1 and octahedral site at 470-430 cm-1. The variation in ac conductivity (σac) with frequency shows that the electrical conductivity in these ferrites is mainly attributed to the electron hopping mechanism.

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

PubMed Central

Chang, Ing-Feng

2013-01-01

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. PMID:23943848

Enhanced adsorption of benzene vapor on granular activated carbon under humid conditions due to shifts in hydrophobicity and total micropore volume.

PubMed

Liu, Han-Bing; Yang, Bing; Xue, Nan-Dong

2016-11-15

A series of hydrophobic-modified (polydimethylsiloxane (PDMS) coating) activated carbons (ACs) were developed to answer a fundamental question: what are the determinants that dominate the adsorption on ACs under humid conditions? Using column experiments, an inter-comparison among bare-AC and PDMS-coated ACs was conducted regarding the association of surface characteristics and adsorption capacity. Primary outcomes occurred in two dominating markers, hydrophobicity and total micropore volume, which played a key role in water adsorption on ACs. However, their contributions to water adsorption on ACs substantially differed under different Pwater/Pair conditions. Hydrophobicity was the only contributor in Pwater/Pair=0.1-0.6, while the two markers contributed equally in Pwater/Pair=0.7-1.0. Furthermore, PDMS-coated AC had a significant increase in benzene adsorption capacities compared to bare-AC at 0-90% relative humidity, while these differences were not significant among PDMS-coated ACs. It is thus presumed that the balance between the two markers can be shifted to favor almost unchanged benzene adsorption capacities among PDMS-coated ACs over a large range of relative humidity. These findings suggest potential benefits of PDMS coating onto ACs in enhancing selective adsorption of hydrophobic volatile organic compounds under high humid conditions. To develop new porous materials with both high total micropore volume and hydrophobicity should thus be considered. Copyright © 2016 Elsevier B.V. All rights reserved.

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.

Radio frequency self-resonant coil for contactless AC-conductivity in 100 T class ultra-strong pulse magnetic fields

NASA Astrophysics Data System (ADS)

Nakamura, D.; Altarawneh, M. M.; Takeyama, S.

2018-03-01

A contactless measurement system of electrical conductivity was developed for application under pulsed high magnetic fields over 100 T by using a self-resonant-type, high-frequency circuit. Electromagnetic fields in the circuit were numerically analysed by the finite element method, to show how the resonant power spectra of the circuit depends on the electrical conductivity of a sample set on the probe-coil. The performance was examined using a high-temperature cuprate superconductor, La2-x Sr x CuO4, in magnetic fields up to 102 T with a high frequency of close to 800 MHz. As a result, the upper critical field could be determined with a good signal-to-noise ratio.

Characterization of mixed-conducting barium cerate-based perovskites for potential fuel cell applications

NASA Astrophysics Data System (ADS)

Mukundan, R.

Chemical modifications of barium cerium gadolinium oxide through the substitution of Bi, Tb, Pr, Nb and Ta were attempted in an effort to increase the p-type or n-type conductivity, and to develop new mixed-conducting electrodes that are chemically compatible with the Ba(Cesb{1-x}Gdsb{x})Osb{3-x/2} electrolyte. The structure, oxygen non-stoichiometry, electronic and ionic-conductivity of several compositions in the doped-barium cerate systems were studied by X-ray diffraction, TGA, DC and AC conductivity, and EMF measurements. The cathodic overpotential of the mixed (electronic/ionic) conducting compositions in this system, on a Ba(Cesb{0.8}Gdsb{0.2})Osb{2.9} electrolyte, were also studied using Current Interruption and AC impedance techniques. The substitution of Bi into Ba(Cesb{0.9}Gdsb{0.1})Osb{2.95} lead to a significant increase in the electronic conductivity, and a total conductivity of about 0.94 S/cm was obtained for Ba(Bisb{0.5}Cesb{0.4}Gdsb{0.1})Osb3 at 800sp°C in air. However, the concentration of oxygen-ion vacancies and hence the ionic conductivity decreased due to the oxidation of Bi to the 5sp{+} state. Compositions in the Ba(Bisb{0.5}Cesb{x}Gdsb{0.5-x})Osb3 system also exhibited significant oxygen non-stoichiometry depending upon the ordering of the B-site cations and the relative concentrations of Ce and Gd. However, the absence of any detectable EMF in the non-stoichiometric compositions implied that the oxygen vacancies are strongly associated with the Bisp{3+} cations. Although highly conductive, chemically stable compositions were prepared in the Ba(Bisb{x}Cesb{y}Gdsb{1-(x+y)})Osb{3-d} system, their ionic conductivities were low. The mixed-conduction properties of Ba(Cesb{1-x}Gdsb{x})Osb{3-d} were enhanced under cathode conditions (600-800sp°C in air) by the substitution of Ce by Tb and Pr. While the substitution of Tb resulted in a decrease in the total conductivity, Pr induced a significant increase in the total conductivity at high Pr levels (≥40 mole%) due to an enhancement of the electronic conductivity. The Ba(Prsb{0.8}Gdsb{0.2})Osb{2.9} sample was found to have the best mixed-conducting properties of all the perovskites evaluated, sigmasb{T}=0.75 S/cm in air at 800sp°C, tsb{H+}=0.15 in a wet argon//dry argon gradient, and tsb{0.2-}≈ 0.05 in a dry air//dry argon gradient. The cathodic overpotentials of the mixed-conducting Pr-doped barium cerates were low, and decreased with increasing ionic and electronic conductivity of the electrode. The lowest overpotential was obtained for the Ba(Prsb{0.8}Gdsb{0.2})Osb{2.9}, cathode, and at low current densities was comparable to that of an optimized porous Pt-electrode. While the substitution of Nb and Ta for Ce lead to an enhancement in the electronic conductivity under reducing conditions associated with the increased reduction of Cesp{4+} to Cesp{3+}, the ionic-conductivity of these perovskites was low. There was no evidence for any protonic conductivity in the 15 mole% Nb and Ta substituted barium cerates. Moreover the anodic overpotential and the anode resistance of these perovskites on a Ba(Cesb{0.8}Gdsb{0.2})Osb{2.9} electrolyte were both high.

Oxygen ionic conductivity of NTE materials of cubic Zr 1- xLn xW 2- yMo yO 8- x/2 (Ln = Er, Yb)

NASA Astrophysics Data System (ADS)

Li, Hai-Hua; Xia, Hai-Ting; Jing, Xi-Ping; Zhao, Xin-Hua

2008-08-01

Cubic Zr 1- xLn xW 2- yMo yO 8- x/2 (Ln = Er: x = 0.01, 0.02, 0.03; y = 0; Ln = Yb: x = 0.02, 0.03; y = 0.4) solid solutions, well-known negative thermal expansion (NTE) materials were prepared by using conventional solid state reactions. The morphology and the composition of the fracture surfaces of the ceramic pellets were determined by SEM and EDX technology. The conductance properties of the pellets, such as conductivity and conductance activation energy, were studied by AC impedance spectroscopy and the materials perform clearly oxygen ionic conduction with the conductivity of about 10 -4 S cm -1 at 673 K, a comparable value to that of ceria based solid electrolytes. The substitution of Mo for W enhanced the thermal stability of ZrW 2O 8, so that the conductivity of Zr 0.98Yb 0.02W 1.6Mo 0.4O 7.99 ceramic can be measured up to 873 K, which is about 5.9 × 10 -4 S cm -1.

Anisotropy of synthetic quartz electrical conductivity at high pressure and temperature

NASA Astrophysics Data System (ADS)

Wang, Duojun; Li, Heping; Yi, Li; Matsuzaki, Takuya; Yoshino, Takashi

2010-09-01

AC measurements of the electrical conductivity of synthetic quartz along various orientations were made between 0.1 and 1 MHz, at ˜855˜1601 K and at 1.0 GPa. In addition, the electrical conductivity of quartz along the c axis has been studied at 1.0-3.0 GPa. The impedance arcs representing bulk conductivity occur in the frequency range of 103-106 Hz, and the electrical responses of the interface between the sample and the electrode occur in the 0.1˜103 Hz range. The pressure has a weak effect on the electrical conductivity. The electrical conductivity experiences no abrupt change near the α - β phase transition point. The electrical conductivity of quartz is highly anisotropic; the electrical conductivity along the c axis is strongest and several orders of magnitude larger than in other directions. The activation enthalpies along various orientations are determined to be 0.6 and 1.2 eV orders of magnitude, respectively. The interpretation of the former is based on the contribution of alkali ions, while the latter effect is attributed to additional unassociated aluminum ions. Comparison of determined anisotropic conductivity of quartz determined with those from field geophysical models shows that the quartz may potentially provide explanations for the behavior of electrical conductivity of anisotropy in the crust that are inferred from the transverse magnetic mode.

Indirect and direct costs of acute coronary syndromes with comorbid atrial fibrillation, heart failure, or both.

PubMed

Ghushchyan, Vahram; Nair, Kavita V; Page, Robert L

2015-01-01

The objective of this study was to determine the direct and indirect costs of acute coronary syndromes (ACS) alone and with common cardiovascular comorbidities. A retrospective analysis was conducted using the Medical Expenditure Panel Survey from 1998 to 2009. Four mutually exclusive cohorts were evaluated: ACS only, ACS with atrial fibrillation (AF), ACS with heart failure (HF), and ACS with both conditions. Direct costs were calculated for all-cause and cardiovascular-related health care resource utilization. Indirect costs were determined from productivity losses from missed days of work. Regression analysis was developed for each outcome controlling for age, US census region, insurance coverage, sex, race, ethnicity, education attainment, family income, and comorbidity burden. A negative binomial regression model was used for health care utilization variables. A Tobit model was utilized for health care costs and productivity loss variables. Total health care costs were greatest for those with ACS and both AF and HF ($38,484±5,191) followed by ACS with HF ($32,871±2,853), ACS with AF ($25,192±2,253), and ACS only ($17,954±563). Compared with the ACS only cohort, the mean all-cause adjusted health care costs associated with ACS with AF, ACS with HF, and ACS with AF and HF were $5,073 (95% confidence interval [CI] 719-9,427), $11,297 (95% CI 5,610-16,985), and $15,761 (95% CI 4,784-26,738) higher, respectively. Average wage losses associated with ACS with and without AF and/or HF amounted to $5,266 (95% CI -7,765, -2,767), when compared with patients without these conditions. ACS imposes a significant economic burden at both the individual and society level, particularly when with comorbid AF and HF.

Relaxation processes and conduction mechanism in bismuth ferrite lead titanate composites

NASA Astrophysics Data System (ADS)

Sahu, Truptimayee; Behera, Banarji

2018-02-01

In this study, samarium (Sm)-doped multiferroic composites of 0.8BiSmxFe1-xO3-0.2PbTiO3 where x = 0.05, 0.10, 0.15, and 0.20 were prepared via the conventional solid state reaction route. The electrical properties of these composites were analyzed using an impedance analyzer over a wide range of temperatures and frequencies (102-106 Hz). The impedance and modulus analyses confirmed the presence of both bulk and grain boundary effects in the materials. The temperature dependence of impedance and modulus spectrum indicated the negative temperature coefficient of resistance behavior. The dielectric relaxation exhibited non-Debye type behavior and it was temperature dependent. The relaxation time (τ) and DC conductivity followed an Arrhenius type behavior. The frequency-dependent AC conductivity obeyed Jonscher's power law. The correlated barrier hopping model was appropriate to understand the conduction mechanism in the composites considered.

Synthesis, Dielectric, Electrical and Optical characterization of ZnO synthesized by chemical route using polymer precursors

NASA Astrophysics Data System (ADS)

Mishra, Raman; Bajpai, P. K.

2011-11-01

Nano-size ZnO (particle size 7.8 nm) have been prepared from a versatile, efficient and technically simple polymer matrix based precursor solution. The precursor solution constituted of zinc nitrates with polymer PVA in presence of mono-/disaccharides. Annealing the precursor mass at 900 °C single phase zinc oxide nano-particles are obtained. X-ray diffraction analysis confirms hexagonal crystal structure with lattice parameter a = b = 3.261 A0, c = 5.220 A0. The estimated average particle size obtained from XRD data is ≈7.8 nm. The impedance analysis reveals that the grain resistance decreases with increase in temperature as expected for a semi-conducting material. The relaxation is polydispersive and conduction is mainly through grains. Optical properties and AC/DC conduction activation energies are estimated from Arrhenius plots and conduction mechanism is discussed.

A study of electrochemical devices based on Agar-Agar-NH4I biopolymer electrolytes

NASA Astrophysics Data System (ADS)

Selvalakshmi, S.; Mathavan, T.; Selvasekarapandian, S.; Premalatha, M.

2018-04-01

A polymer electrolyte system has been developed using a biopolymer namely, Agar-Agar in combination with ammonium iodide in different weight percentages by solution casting technique. The films were characterized electrically by AC Impedance Spectroscopy for its conductivity. The highest conductivity achieved at room temperature was for 50 wt. % agar-agar: 50 wt. % NH4I with a conductivity value of 1.20 × 10-4 Scm-1. An electrochemical cell was fabricated in the configuration of: Zn + ZnSO4.7H2O + graphite (anode) | 50 wt. % (Agar-agar): 50 wt. % NH4I (electrolyte) | PbO2 + V2O5 + graphite (cathode) and it produced a maximum open circuit voltage of 1.73 V. A single PEM fuel cell was constructed with the highest conducting sample (50 wt. % (Agar-agar): 50 wt. % NH4I) and it exhibited an output voltage of 408mV.

Physicochemical and adsorptive characteristics of activated carbons from waste polyester textiles utilizing MgO template method.

PubMed

Xu, Zhihua; Zhang, Daofang; Yuan, Zhihang; Chen, Weifang; Zhang, Tianqi; Tian, Danqi; Deng, Haixuan

2017-10-01

Activated carbons with high specific surface areas were produced, utilizing waste polyester textiles as carbon precursor by magnesium oxide (MgO) template method. Magnesium chloride (MgCl 2 ), magnesium citrate (MgCi), and MgO were employed as MgO precursors to prepare activated carbons (AC-MgCl 2 , AC-MgCi, and AC-MgO). Thermogravimetry-differential scanning calorimetry was conducted to investigate the pore-forming mechanism, and N 2 adsorption/desorption isotherms, XRD, SEM-EDS, TEM, FTIR and pH pzc were achieved to analyze physicochemical characteristics of the samples. The specific surface areas of AC-MgCl 2 (1173 m 2 /g) and AC-MgCi (1336 m 2 /g) were much higher than that of AC-MgO (450 m 2 /g), and the pores sizes of which were micro-mesoporous, mesoporous, and macropores, respectively, due to the formation of MgO crystal with different sizes. All activated carbons had abundant acidic oxygen groups. In addition, batch adsorption experiments were carried out to investigate the adsorptive characteristics of the prepared activated carbons toward Cr(VI). The adsorption kinetics fitted well with the pseudo-second order, and the adsorptive capacity of AC-MgCl 2 (42.55 mg/g) was higher than those of AC-MgCi (40.93 mg/g) and AC-MgO (35.87 mg/g).

A systematic review of the quality of economic models comparing thrombosis inhibitors in patients with acute coronary syndrome undergoing percutaneous coronary intervention.

PubMed

Hatz, Maximilian H M; Leidl, Reiner; Yates, Nichola A; Stollenwerk, Björn

2014-04-01

Thrombosis inhibitors can be used to treat acute coronary syndromes (ACS). However, there are various alternative treatment strategies, of which some have been compared using health economic decision models. To assess the quality of health economic decision models comparing thrombosis inhibitors in patients with ACS undergoing percutaneous coronary intervention, and to identify areas for quality improvement. The literature databases MEDLINE, EMBASE, EconLit, National Health Service Economic Evaluation Database (NHS EED), Database of Abstracts of Reviews of Effects (DARE) and Health Technology Assessment (HTA). A review of the quality of health economic decision models was conducted by two independent reviewers, using the Philips checklist. Twenty-one relevant studies were identified. Differences were apparent regarding the model type (six decision trees, four Markov models, eight combinations, three undefined models), the model structure (types of events, Markov states) and the incorporation of data (efficacy, cost and utility data). Critical issues were the absence of particular events (e.g. thrombocytopenia, stroke) and questionable usage of utility values within some studies. As we restricted our search to health economic decision models comparing thrombosis inhibitors, interesting aspects related to the quality of studies of adjacent medical areas that compared stents or procedures could have been missed. This review identified areas where recommendations are indicated regarding the quality of future ACS decision models. For example, all critical events and relevant treatment options should be included. Models also need to allow for changing event probabilities to correctly reflect ACS and to incorporate appropriate, age-specific utility values and decrements when conducting cost-utility analyses.

Does "smoker's paradox" exist in clopidogrel-treated Turkish patients with acute coronary syndrome.

PubMed

Edem, Efe; Kirdök, Ali Hikmet; Kınay, Ahmet Ozan; Tekin, Ümit İlker; Taş, Sedat; Alpaslan, Erkan; Pabuccu, Mustafa Türker; Akdeniz, Bahri

2016-01-01

Previously conducted studies revealed that smoking enhanced the efficacy of clopidogrel by increasing formation of the active metabolite (AM) from the prodrug through induction of the cytochrome CYP1A2. The expression of cytochrome enzymes depends on genotype and no data exists in literature conducted in Turkish patients comparing the clopidogrel responsiveness between active smokers and non-active smokers treated with clopidogrel. In this study, our aim was to investigate the clopidogrel responsiveness in clopidogrel-treated Turkish acute coronary syndrome (ACS) patients according to their smoking status. We retrospectively enrolled 258 patients who were hospitalized due to ACS. Clinical variables of the patients, especially smoking status were recorded. Clopidogrel resistance was evaluated by using adenosine diphosphate (ADP) induced platelet aggregometry. Clopidogrel resistance was detected as a change in maximal aggregation ≤20% from baseline. A total of 139 patients were active smokers while 12 were former smokers. 107 patients did not have a history of smoking. Ten of the smokers were hyporesponsive to clopidogrel, whereas 36 of non-smokers were hyporesponsive to clopidogrel (p < 0.001). Receiver-operating characteristic curve analysis demonstrated that Au-min value >612.5 predicted the clopidogrel resistance with a sensitivity of 60% (OR: 100.65, %95 CI = 19.996-506.615 p < 0.001). Results of this study demonstrated that ADP responses were lower in smokers receiving clopidogrel and aspirin than in non-smokers receiving the same drug regimen. This finding indicates that smoking was related to an enhanced clopidogrel responsiveness in Turkish patients hospitalized due to ACS, suggesting that "smoker's paradox" probably exists in Turkish ACS patients.

Validation of contractor HMA testing data in the materials acceptance process - phase II : final report.

DOT National Transportation Integrated Search

2016-08-01

This study conducted an analysis of the SCDOT HMA specification. A Research Steering Committee provided oversight : of the process. The research process included extensive statistical analyses of test data supplied by SCDOT. : A total of 2,789 AC tes...

Temperature and frequency response of conductivity in Ag2S doped chalcogenide glassy semiconductor

NASA Astrophysics Data System (ADS)

Ojha, Swarupa; Das, Anindya Sundar; Roy, Madhab; Bhattacharya, Sanjib

2018-06-01

The electric conductivity of chalcogenide glassy semiconductor xAg2S-(1-x)(0.5S-0.5Te) has been presented here as a function of temperature and frequency. Formation of different nanocrystallites has been confirmed from X-ray diffraction study. It is also noteworthy that average size of nanocrystallites decreases with the increase of dislocation density. Dc conductivity data have been interpreted using Mott's model and Greaves's model in low and high temperature regions respectively. Ac conductivity above the room temperature has been analyzed using Meyer-Neldel (MN) conduction rule. It is interestingly noted that Correlated Barrier Hopping (CBH) model is the most appropriate conduction mechanism for x = 0.35, where pairs of charge carrier are considered to hop over the potential barrier between the sites via thermal activation. To interpret experimental data for x = 0.45, modified non-overlapping small polaron tunnelling (NSPT) model is supposed to be appropriate model due to tunnelling through grain boundary. The conductivity spectra at various temperatures have been analyzed using Almond-West Formalism (power law model). Scaling of conductivity spectra reveals that electrical relaxation process of charge carriers (polaron) is temperature independent but depends upon the composition of the present chalcogenide glassy system.

A study on the effect of prolonged mobile phone use on pure tone audiometry thresholds of medical students of Sikkim

PubMed Central

Das, S; Chakraborty, S; Mahanta, B

2017-01-01

Introduction: Mobile phones have become indispensable for daily activities, and people are exposed to them from an early age. There is, however, concern about the harmful effect of the electromagnetic radiation emitted from the mobile phones. Objective: The objective of the study was to study the effect of mobile phone on average pure tone audiometry (PTA) threshold of the person and to study the changes in the pure tone threshold at high frequencies such as 2 kHz, 4 kHz, and 8 kHz among the students with prolonged exposure to mobile phones. Methodology: A cross-sectional study was conducted among the medical students who have been using mobile phones for the past 5 years. The effect of mobile phones on the PTA threshold in the exposed ear and the nonexposed ear was assessed. Results: The study shows that there is a significant difference in average air conduction (AC) and bone conduction (BC) hearing threshold among the exposed and the nonexposed ears (P < 0.05). A significant rise of both AC and BC threshold at individual frequencies between the exposed and the nonexposed ear is also noted in this study. Conclusion: The study conducted shows changes in the hearing threshold of the exposed ear when compared with the nonexposed ear. There are however lot of unanswered questions which provide an interesting avenue for further research. Till concrete evidence is available the only feasible way to control its exposure is to limit the duration of usage of mobile phones. PMID:28272071

Ac Conduction in Mixed Oxides Al-In2O3-SnO2-Al Structure Deposited by Co-Evaporation

NASA Astrophysics Data System (ADS)

Anwar, M.; Siddiqi, S. A.; Ghauri, I. M.

Conductivity-frequency and capacitance-frequency characteristics of mixed oxides Al-In2O3-SnO2-Al structure are examined to elicit any correlation with the conduction mechanisms most often observed in thin film work. The existence of Schottky barriers is believed to be due to a strong donor band in the insulator established during the vacuum evaporation when a layer of mixed oxides In2O3-SnO2 system is sandwiched between two metal electrodes. Low values of activation energy at low temperatures indicate that the transport of the carriers between localized states is mainly due to electronic hopping over the barrier separating the two nearest neighbor sites. The increase in the formation of ionized donors with increase in temperature during electrical measurements indicates that electronic part of the conductivity is higher than the ionic part. The initial increase in conductivity with increase in Sn content in In2O3 lattice is caused by the Sn atom substitution of In atom, giving out one extra electron. The decrease in electrical conductivity above the critical Sn content (10 mol% SnO2) is caused by the defects formed by Sn atoms, which act as carrier traps rather than electron donors. The increase in electrical conductivity with film thickness is caused by the increase in free carriers density, which is generated by oxygen vacancy acting as two electron donor. The increase in conductivity with substrate and annealing temperatures is due to either the severe deficiency of oxygen, which deteriorates the film properties and reduces the mobility of the carriers or to the diffusion of Sn atoms from interstitial locations into the In cation sites and formation of indium species of lower oxidation state (In2+). Calculations of C and σac from tan δ measurements suggest that there is some kind of space-charge polarization in the material, caused by the storage of carriers at the electrodes. Capacitance decreases not only with the rise of frequency but also with the lowering of temperature. At low temperatures the major contribution to capacitance arises from the ionic polarization, however, with the increase of temperature the contribution from orientation polarization would considerably increase. The decrease in capacitance with the increase in frequency may be attributed to interfacial polarization.

Software Toolbox for Low-Frequency Conductivity and Current Density Imaging Using MRI.

PubMed

Sajib, Saurav Z K; Katoch, Nitish; Kim, Hyung Joong; Kwon, Oh In; Woo, Eung Je

2017-11-01

Low-frequency conductivity and current density imaging using MRI includes magnetic resonance electrical impedance tomography (MREIT), diffusion tensor MREIT (DT-MREIT), conductivity tensor imaging (CTI), and magnetic resonance current density imaging (MRCDI). MRCDI and MREIT provide current density and isotropic conductivity images, respectively, using current-injection phase MRI techniques. DT-MREIT produces anisotropic conductivity tensor images by incorporating diffusion weighted MRI into MREIT. These current-injection techniques are finding clinical applications in diagnostic imaging and also in transcranial direct current stimulation (tDCS), deep brain stimulation (DBS), and electroporation where treatment currents can function as imaging currents. To avoid adverse effects of nerve and muscle stimulations due to injected currents, conductivity tensor imaging (CTI) utilizes B1 mapping and multi-b diffusion weighted MRI to produce low-frequency anisotropic conductivity tensor images without injecting current. This paper describes numerical implementations of several key mathematical functions for conductivity and current density image reconstructions in MRCDI, MREIT, DT-MREIT, and CTI. To facilitate experimental studies of clinical applications, we developed a software toolbox for these low-frequency conductivity and current density imaging methods. This MR-based conductivity imaging (MRCI) toolbox includes 11 toolbox functions which can be used in the MATLAB environment. The MRCI toolbox is available at http://iirc.khu.ac.kr/software.html . Its functions were tested by using several experimental datasets, which are provided together with the toolbox. Users of the toolbox can focus on experimental designs and interpretations of reconstructed images instead of developing their own image reconstruction softwares. We expect more toolbox functions to be added from future research outcomes. Low-frequency conductivity and current density imaging using MRI includes magnetic resonance electrical impedance tomography (MREIT), diffusion tensor MREIT (DT-MREIT), conductivity tensor imaging (CTI), and magnetic resonance current density imaging (MRCDI). MRCDI and MREIT provide current density and isotropic conductivity images, respectively, using current-injection phase MRI techniques. DT-MREIT produces anisotropic conductivity tensor images by incorporating diffusion weighted MRI into MREIT. These current-injection techniques are finding clinical applications in diagnostic imaging and also in transcranial direct current stimulation (tDCS), deep brain stimulation (DBS), and electroporation where treatment currents can function as imaging currents. To avoid adverse effects of nerve and muscle stimulations due to injected currents, conductivity tensor imaging (CTI) utilizes B1 mapping and multi-b diffusion weighted MRI to produce low-frequency anisotropic conductivity tensor images without injecting current. This paper describes numerical implementations of several key mathematical functions for conductivity and current density image reconstructions in MRCDI, MREIT, DT-MREIT, and CTI. To facilitate experimental studies of clinical applications, we developed a software toolbox for these low-frequency conductivity and current density imaging methods. This MR-based conductivity imaging (MRCI) toolbox includes 11 toolbox functions which can be used in the MATLAB environment. The MRCI toolbox is available at http://iirc.khu.ac.kr/software.html . Its functions were tested by using several experimental datasets, which are provided together with the toolbox. Users of the toolbox can focus on experimental designs and interpretations of reconstructed images instead of developing their own image reconstruction softwares. We expect more toolbox functions to be added from future research outcomes.

In Situ Mechanical Property Measurements of Amorphous Carbon-Boron Nitride Nanotube Nanostructures

NASA Technical Reports Server (NTRS)

Kim, Jae-Woo; Lin, Yi; Nunez, Jennifer Carpena; Siochi, Emilie J.; Wise, Kristopher E.; Connell, John W.; Smith, Michael W.

2011-01-01

To understand the mechanical properties of amorphous carbon (a-C)/boron nitride nanotube (BNNT) nanostructures, in situ mechanical tests are conducted inside a transmission electron microscope equipped with an integrated atomic force microscope system. The nanotube structure is modified with amorphous carbon deposited by controlled electron beam irradiation. We demonstrate multiple in situ tensile, compressive, and lap shear tests with a-C/BNNT hybrid nanostructures. The tensile strength of the a-C/BNNT hybrid nanostructure is 5.29 GPa with about 90 vol% of a-C. The tensile strength and strain of the end-to-end joint structure with a-C welding is 0.8 GPa and 5.2% whereas the lap shear strength of the side-by-side joint structure with a-C is 0.25 GPa.

77 FR 7080 - Changes To Implement Transitional Program for Covered Business Method Patents

Federal Register 2010, 2011, 2012, 2013, 2014

2012-02-10

... 0651-AC73 Changes To Implement Transitional Program for Covered Business Method Patents AGENCY: United... covered business method patents to be conducted before the Patent Trial and Appeal Board (Board). These..., Covered Business Method Patent Review Proposed Rules.'' Comments may also be sent by electronic mail...

An EPG waveform library for sharpshooters and preliminary effects of applied voltage on behaviors controlling Xylella fastidiosa inoculation

USDA-ARS?s Scientific Manuscript database

Electropenetrography (EPG) waveforms represent electrical conductivity of fluids flowing through an insect’s mouthparts. Over the 50 years since its invention, EPG has undergone three major electronic transformations. The newest, third generation of electropenetrograph, the AC-DC EPG monitor, offers...

78 FR 58613 - Affirmative Action and Nondiscrimination Obligations of Contractors and Subcontractors Regarding...

Federal Register 2010, 2011, 2012, 2013, 2014

2013-09-24

... for age and race in a regression analysis. Using America Community Survey (ACS) data and conducting a.... All models were run using the American Community Survey 2008-2010 Public Use Microdata (PUMS). The... that contractors maintain several quantitative measurements and comparisons for the number of veterans...

77 FR 7060 - Changes To Implement Post-Grant Review Proceedings

Federal Register 2010, 2011, 2012, 2013, 2014

2012-02-10

... 0651-AC72 Changes To Implement Post-Grant Review Proceedings AGENCY: United States Patent and Trademark... Invents Act that create a new post-grant review proceeding to be conducted before the Patent Trial and... mail message over the Internet addressed to: post[email protected] . Comments may also be...

A novel technique for the treatment of stages III to IV hemorrhoids: Homemade anal cushion suspension clamp combined with harmonic scalpel.

PubMed

Lin, Guoqiang; Ge, Qiongxiang; He, Xiaokang; Qi, Haixin; Xu, Li

2017-06-01

To compare the efficacy of homemade anal cushion suspension clamp combined with harmonic scalpel (ACS) and Milligan-Morgan hemorrhoidectomy combined with electric knife (MMH) in the treatment of stages III to IV hemorrhoids. We conducted a retrospective study of 99 patients with stages III to IV hemorrhoids hospitalized from January to December in 2013. Among them, 51 patients were treated with ACS, while 48 patients received MMH. Data from clinical recording and follow-up included operative time, intraoperative blood loss, hospitalization information, postoperative pain, and postoperative complications. Operative time, intraoperative blood loss and hospitalization time in ACS group were significantly less than those in MMH group (P < .05). Compared with MMH group, ACS group had a lower postoperative static pain score from days 1 to 14 (P < .01). The patients in ACS group exhibited less postoperative defecation pain scores from days 3 to 20 than those of MMH group (P < .05). The incidence of postoperative anal edema and delayed wound healing in ACS group was lower than that in MMH group (P < .05). Compared with MMH, our novel technique ACS was more effective and had fewer postoperative complications in the treatment of stages III to IV hemorrhoids.

A novel technique for the treatment of stages III to IV hemorrhoids

PubMed Central

Lin, Guoqiang; Ge, Qiongxiang; He, Xiaokang; Qi, Haixin; Xu, Li

2017-01-01

Abstract To compare the efficacy of homemade anal cushion suspension clamp combined with harmonic scalpel (ACS) and Milligan–Morgan hemorrhoidectomy combined with electric knife (MMH) in the treatment of stages III to IV hemorrhoids. We conducted a retrospective study of 99 patients with stages III to IV hemorrhoids hospitalized from January to December in 2013. Among them, 51 patients were treated with ACS, while 48 patients received MMH. Data from clinical recording and follow-up included operative time, intraoperative blood loss, hospitalization information, postoperative pain, and postoperative complications. Operative time, intraoperative blood loss and hospitalization time in ACS group were significantly less than those in MMH group (P < .05). Compared with MMH group, ACS group had a lower postoperative static pain score from days 1 to 14 (P < .01). The patients in ACS group exhibited less postoperative defecation pain scores from days 3 to 20 than those of MMH group (P < .05). The incidence of postoperative anal edema and delayed wound healing in ACS group was lower than that in MMH group (P < .05). Compared with MMH, our novel technique ACS was more effective and had fewer postoperative complications in the treatment of stages III to IV hemorrhoids. PMID:28658138

A Study of Carbon Nanofibers and Active Carbon as Symmetric Supercapacitor in Aqueous Electrolyte: A Comparative Study

NASA Astrophysics Data System (ADS)

Daraghmeh, Allan; Hussain, Shahzad; Saadeddin, Iyad; Servera, Llorenç; Xuriguera, Elena; Cornet, Albert; Cirera, Albert

2017-12-01

Symmetric supercapacitors are fabricated by carbon nanofibers (CNF) and activated carbon (AC) using similar proportions of 7 wt% polyvinylidene fluoride (PVDF) polymer binder in an aqueous electrolyte. In this study, a comparison of porous texture and electrochemical performances between CNFs and AC based supercapacitors was carried out. Electrodes were assembled in the cell without a current collector. The prepared electrodes of CNFs and AC present Brunauer-Emmett-Teller (BET) surface area of 83 and 1042 m2/g, respectively. The dominant pore structure for CNFs is mesoporous while for AC is micropore. The results showed that AC provided higher specific capacitance retention up to very fast scan rate of 500 mV/s. AC carbon had a specific capacitance of 334 F/g, and CNFs had 52 F/g at scan rate 5 mV/s in aqueous solution. Also, the results indicate the superior conductivity of CNFs in contrast to AC counterparts. The measured equivalent series resistance (ESR) showed a very small value for CNFs (0.28 Ω) in comparison to AC that has an ESR resistance of (3.72 Ω). Moreover, CNF delivered higher specific power (1860 W/kg) than that for AC (450 W/kg). On the other hand, AC gave higher specific energy (18.1 Wh/kg) than that for CNFs (2 Wh/kg).This indicates that the AC is good for energy applications. Whereas, CNF is good for power application. Indeed, the higher surface area will lead to higher specific capacitance and hence higher energy density for AC. For CNF, lower ESR is responsible for having higher power density. Both CNF and AC supercapacitor exhibit an excellent charge-discharge stability up to 2500 cycles.

Inter-rater reliability of direct observations of the physical and psychosocial working conditions in eldercare: An evaluation in the DOSES project.

PubMed

Karstad, Kristina; Rugulies, Reiner; Skotte, Jørgen; Munch, Pernille Kold; Greiner, Birgit A; Burdorf, Alex; Søgaard, Karen; Holtermann, Andreas

2018-05-01

The aim of the study was to develop and evaluate the reliability of the "Danish observational study of eldercare work and musculoskeletal disorders" (DOSES) observation instrument to assess physical and psychosocial risk factors for musculoskeletal disorders (MSD) in eldercare work. During 1.5 years, sixteen raters conducted 117 inter-rater observations from 11 nursing homes. Reliability was evaluated using percent agreement and Gwet's AC1 coefficient. Of the 18 examined items, inter-rater reliability was excellent for 7 items (AC1>0.75) fair to good for 7 items (AC1 0.40-0.75) and poor for 2 items (AC1 0-0.40). For 2 items there was no agreement between the raters (AC1 <0). The reliability did not differ between the first and second half of the data collection period and the inter-rater observations were representative regarding occurrence of events in eldercare work. The instrument is appropriate for assessing physical and psychosocial risk factors for MSD among eldercare workers. Copyright © 2018 The Authors. Published by Elsevier Ltd.. All rights reserved.

An examination of the psychometric properties of the Rosenberg Self-Esteem Scale (RSES) in Chinese acute coronary syndrome (ACS) patients.

PubMed

Martin, Colin R; Thompson, David R; Chan, Dominic S

2006-11-01

The psychometric properties of the Rosenberg Self-Esteem Scale (RSES) as a clinical research instrument for acute coronary syndrome (ACS) patients were investigated in a translated Chinese version of the instrument. A confirmatory factor analysis was conducted on the RSES to establish its psychometric properties in 128 ACS patients over two observation points (within 1 week and 6 months post-admission for ACS). Internal and test-retest reliability of the RSES-TOT (all-items) and RSES-POS sub-scale (positively valenced items) were found to be acceptable. The RSES-NEG sub-scale (negatively valenced items) lacked acceptable internal reliability. The underlying factor structure of the RSES comprised two distinct but related factors, though there was inconsistency in best model fit indices at the 1-week observation point. The use of the RSES as two sub-scales (RSES-POS and RSES-NEG) may be clinically useful in evaluating the influence of this important psychological construct on the health outcomes of patients with ACS. Directions for future research are indicated.

Vinpocetine Inhibits Streptococcus pneumoniae–Induced Upregulation of Mucin MUC5AC Expression via Induction of MKP-1 Phosphatase in the Pathogenesis of Otitis Media

PubMed Central

Lee, Ji-Yun; Komatsu, Kensei; Lee, Byung-Cheol; Miyata, Masanori; O’Neill Bohn, Ashley; Xu, Haidong

2015-01-01

Mucin overproduction is a hallmark of otitis media (OM). Streptococcus pneumoniae is one of the most common bacterial pathogens causing OM. Mucin MUC5AC plays an important role in mucociliary clearance of bacterial pathogens. However, if uncontrolled, excessive mucus contributes significantly to conductive hearing loss. Currently, there is a lack of effective therapeutic agents that suppress mucus overproduction. In this study, we show that a currently existing antistroke drug, vinpocetine, a derivative of the alkaloid vincamine, inhibited S. pneumoniae–induced mucin MUC5AC upregulation in cultured middle ear epithelial cells and in the middle ear of mice. Moreover, vinpocetine inhibited MUC5AC upregulation by inhibiting the MAPK ERK pathway in an MKP-1–dependent manner. Importantly, ototopical administration of vinpocetine postinfection inhibited MUC5AC expression and middle ear inflammation induced by S. pneumoniae and reduced hearing loss and pneumococcal loads in a well-established mouse model of OM. Thus, these studies identified vinpocetine as a potential therapeutic agent for inhibiting mucus production in the pathogenesis of OM. PMID:25972475

Studies on activated carbon derived from neem (azadirachta indica) bio-waste, and its application as supercapacitor electrode

NASA Astrophysics Data System (ADS)

Ahmed, Sultan; Parvaz, M.; Johari, Rahul; Rafat, M.

2018-04-01

The present study reports the preparation of quasi solid-state supercapacitor employing activated carbon (AC) electrodes and gel polymer electrolyte (GPE). AC was derived from Neem leaves by means of chemical activation using zinc chloride as activating agent. GPE was prepared using solution-cast technique and comprises of LiClO 4 salt, dispersed in EC:PC (1:1 vol.) and entrapped in PVdF-HFP solution. Extensive physical and electrochemical characterization of synthesized AC and GPE was done. AC was characterized using the techniques of SEM, TEM, XRD, Raman spectroscopy, TGA and BET tests while GPE was characterized by electrochemical stability window (ESW) and conductivity test. The fabricated supercapacitor cell was tested using standard electrochemical characterization techniques. It was found that the fabricated cell offers high values of specific capacitance (74.41 F g‑1), specific energy (10.33 Wh kg‑1) and specific power (4.66 kW kg‑1). These results demonstrate the suitability of prepared AC as promising electrode material for supercapacitor applications.

Critical frequency for coalescence of emulsions in an AC electric field

NASA Astrophysics Data System (ADS)

Liu, Zhou; Ali, Faizi Hammad; Shum, Ho Cheung

2017-11-01

Applying an electric field to trigger the coalescence of emulsions has been applied in various applications which include crude oil recovery, emulsion stability characterization as well as pico-injection and droplet-based chemical reaction in microfluidics. In this work, we systematically investigated the responses of surfactant-stabilized emulsions to a controlled AC electric field using a customer-built chip. At a given amplitude of the AC voltage, we found a critical frequency beyond which the emulsions remain stable. When the frequency is decreased to below the critical value, emulsions coalesce immediately. Such critical frequency is found to be dependent of amplitude of the AC voltage, viscosity of the fluids, concentration and type of the surfactant as well as the electric conductivity of the droplet phase. Using a model based on the drainage of thin film, we have explored the mechanism behind and interpret this phenomenon systematically. Our work extends the understanding of the electro-coalescence of emulsions and can be beneficial for any applications involve the coalescence of droplets in an AC electric field.

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. Copyright 2010 Elsevier B.V. All rights reserved.

A randomized trial of the effect of automated ventricular capture on device longevity and threshold measurement in pacemaker patients.

PubMed

Koplan, Bruce A; Gilligan, David M; Nguyen, Luc S; Lau, Theodore K; Thackeray, Lisa M; Berg, Kellie Chase

2008-11-01

An automatic capture (AC) algorithm adjusts ventricular pacing output to capture the ventricle while optimizing output to 0.5 V above threshold. AC maintains this output and confirms capture on a beat-to-beat basis in bipolar and unipolar pacing and sensing. To assess the AC algorithm and its impact on device longevity. Patients implanted with a pacemaker were randomized 1:1 to have the AC feature on or off for 12 months. Two threshold tests were conducted at each visit- automatic threshold and manual threshold. Average ventricular voltage output and projected device longevity were compared between AC on and off using nonparametric tests. Nine hundred ten patients were enrolled and underwent device implantation. Average ventricular voltage output was 1.6 V for the AC on arm (n = 444) and 3.1 V for the AC off arm (n = 446) (P < 0.001). Projected device longevity was 10.3 years for AC on and 8.9 years for AC off (P < 0.0001), or a 16% increase in longevity for AC on. The proportion of patients in whom there was a difference between automatic threshold and manual threshold of

Multiple piezo-patch energy harvesters on a thin plate with respective AC-DC conversion

NASA Astrophysics Data System (ADS)

Aghakhani, Amirreza; Basdogan, Ipek

2018-03-01

Piezoelectric patch energy harvesters can be directly integrated to plate-like structures which are widely used in automotive, marine and aerospace applications, to convert vibrational energy to electrical energy. This paper presents two different AC-DC conversion techniques for multiple patch harvesters, namely single rectifier and respective rectifiers. The first case considers all the piezo-patches are connected in parallel to a single rectifier, whereas in the second case, each harvester is respectively rectified and then connected in parallel to a smoothing capacitor and a resistive load. The latter configuration of AC-DC conversion helps to avoid the electrical charge cancellation which is a problem with the multiple harvesters attached to different locations of the host plate surface. Equivalent circuit model of the multiple piezo-patch harvesters is developed in the SPICE software to simulate the electrical response. The system parameters are obtained from the modal analysis solution of the plate. Simulations of the voltage frequency response functions (FRFs) for the standard AC input - AC output case are conducted and validated by experimental data. Finally, for the AC input - DC output case, numerical simulation and experimental results of the power outputs of multiple piezo-patch harvesters with multiple AC-DC converters are obtained for a wide range of resistive loads and compared with the same array of harvesters connected to a single AC-DC converter.

Self-supporting activated carbon/carbon nanotube/reduced graphene oxide flexible electrode for high performance supercapacitor

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Xing; Tang, Yao; Song, Junhua

A self-supporting and flexible activated carbon/carbon nanotube/reduced graphene oxide (AC/CNT/RGO) film has been rationally designed for constructing high-performance supercapacitor. We prepared the AC/CNT/RGO film by anchoring the AC particles with a 3D and porous framework built by hierarchically weaving the 1 D CNT and 2D RGO using their intrinsic van der Waals force. The CNT network is beneficial for improving the electronic conductivity of the electrode, while the AC particles could effectively suppress the aggregation of RGO and CNT due to their blocking effect. The synergistic effects among the AC, CNT and RGO validate the AC/CNT/RGO as a promising electrodemore » for supercapacitor, exhibiting greatly enhanced electrochemical performances in comparison with the pure RGO film, pure CNT film and AC electrode. Furthermore, the AC/CNT/RGO electrode delivers a high specific capacitance of 101 F g -1 at the current density of 0.2 A g -1 offering a maximum energy density of 30.0 W h kg -1 in organic electrolyte at the cut-off voltage range of 0.001–3.0 V. The findings of this work open a new avenue for the design of self-supporting electrodes for the development of flexible and light weight energy storage supercapacitor.« less

Self-supporting activated carbon/carbon nanotube/reduced graphene oxide flexible electrode for high performance supercapacitor

DOE PAGES

Li, Xing; Tang, Yao; Song, Junhua; ...

2017-12-06

A self-supporting and flexible activated carbon/carbon nanotube/reduced graphene oxide (AC/CNT/RGO) film has been rationally designed for constructing high-performance supercapacitor. We prepared the AC/CNT/RGO film by anchoring the AC particles with a 3D and porous framework built by hierarchically weaving the 1 D CNT and 2D RGO using their intrinsic van der Waals force. The CNT network is beneficial for improving the electronic conductivity of the electrode, while the AC particles could effectively suppress the aggregation of RGO and CNT due to their blocking effect. The synergistic effects among the AC, CNT and RGO validate the AC/CNT/RGO as a promising electrodemore » for supercapacitor, exhibiting greatly enhanced electrochemical performances in comparison with the pure RGO film, pure CNT film and AC electrode. Furthermore, the AC/CNT/RGO electrode delivers a high specific capacitance of 101 F g -1 at the current density of 0.2 A g -1 offering a maximum energy density of 30.0 W h kg -1 in organic electrolyte at the cut-off voltage range of 0.001–3.0 V. The findings of this work open a new avenue for the design of self-supporting electrodes for the development of flexible and light weight energy storage supercapacitor.« less

Ethnic differences in beta-cell function, dietary intake and expression of the metabolic syndrome among UK adults of South Asian, black African-Caribbean and white-European origin at high risk of metabolic syndrome.

PubMed

Goff, Louise M; Griffin, Bruce A; Lovegrove, Julie A; Sanders, Tom A; Jebb, Susan A; Bluck, Les J; Frost, Gary S

2013-07-01

A cross-sectional analysis of ethnic differences in dietary intake, insulin sensitivity and beta-cell function, using the intravenous glucose tolerance test (IVGTT), was conducted on 497 healthy adult participants of the 'Reading, Imperial, Surrey, Cambridge, and Kings' (RISCK) study. Insulin sensitivity (Si) was significantly lower in African-Caribbean (AC) and South Asian (SA) participants [IVGTT-Si; AC: 2.13 vs SA: 2.25 vs white-European (WE): 2.84 (×10(-4) mL µU min)(2), p < 0.001]. AC participants had a higher prevalence of anti-hypertensive therapy (AC: 19.7% vs SA: 7.5%), the most cardioprotective lipid profile [total:high-density lipoprotein (HDL); AC: 3.52 vs SA: 4.08 vs WE: 3.83, p = 0.03] and more pronounced hyperinsulinaemia [IVGTT-acute insulin response (AIR)] [AC: 575 vs SA: 428 vs WE: 344 mL/µU/min)(2), p = 0.002], specifically in female participants. Intake of saturated fat and carbohydrate was lower and higher in AC (10.9% and 50.4%) and SA (11.1% and 52.3%), respectively, compared to WE (13.6% and 43.8%, p < 0.001). Insulin resistance in ACs is characterised by 'normal' lipid profiles but high rates of hypertension and pronounced hyperinsulinaemia.

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.

Involvement of Tetrahymena pyriformis and selected fungi in the elimination of anthracene, and toxicity assessment of the biotransformation products.

PubMed

Guiraud, P; Bonnet, J L; Boumendjel, A; Kadri-Dakir, M; Dusser, M; Bohatier, J; Steiman, R

2008-02-01

Anthracene (AC) is a non-mutagenic and non-carcinogenic, low-molecular-weight polycyclic aromatic hydrocarbon present in the environment. Its toxicity can be dramatically increased after solar-light exposure. Biotransformation capacities of AC by Tetrahymena pyriformis and a selection of eight micromycetes were studied, and the ability of these microorganisms to detoxify the polluted ecosystems was assessed. We showed that T. pyriformis was able to accumulate high amounts of AC without any transformation. In contrast, the fungi Cunninghamella elegans, Absidia fusca, Absidia cylindrospora, Rhodotorula glutinis, and Aspergillus terreus were able to transform AC with a high efficiency. Cytotoxicity assays conducted on HeLa cells and T. pyriformis showed that crude extract from A. fusca culture medium obtained after AC biotransformation was not toxic. For A. fusca and A. cylindrospora, 1-4 dihydroxyanthraquinone was shown to be the major product during the biotransformation process. This compound seemed to be a dead-end metabolite at least for the Absidia strains. The cytotoxicity of 1-4 dihydroxyanthraquinone was higher than that of AC to T. pyriformis but lower to HeLa cells. On the whole our results showed that the microorganisms studied were all able to decontaminate an AC-polluted ecosystem, either by accumulating or transforming the compound. A possible detoxification process resulting from AC biotransformation can be considered only using the human cell model.

Studies on the effect of dispersoid(ZrO2) in PVdF-co-HFP based gel polymer electrolytes

NASA Astrophysics Data System (ADS)

Sivakumar, M.; Subadevi, R.; Muthupradeepa, R.

2013-06-01

Gel polymer electrolytes containing poly(vinylidenefluoride-co-hexafluoropropylene) (P(VdF-co-HFP)) / Lithium bis(trifluoromethane sulfon)imide (LiTFSI) / mixture of ethylene carbonate and propylene carbonate (EC+PC) with different concendration of ZrO2 has been prepared using the solution casting technique. The conductivity of the prepared electrolyte sample has been determined by AC impedance technique in the range 303-353K. The temperature dependent ionic conductivity plot seems to obey VTF relation. The maximum ionic conductivity value of 4.46 × 10-3S/cm has been obtained for PVdF-co-HFP(32%) - LiTFSI(8%) - EC+PC (60%) + ZrO2(6wt%) based polymer electrolyte. The surface morphology of the prepared electrolyte sample has been studied using SEM.

Conductivity and Dielectric Relaxation Properties of Annealed Cr-Substituted Ni-Ferrite Nanoparticles

NASA Astrophysics Data System (ADS)

El-Ghazzawy, E. H.

2017-10-01

Nanocrystalline NiCr x Fe2- x O4 spinel samples with x = 0.1 and 0.2 have been synthesized by coprecipitation method and annealed at 620°C and 1175°C for 4 h. Their electrical properties were investigated as functions of frequency in the range of 100 Hz to 100 kHz and temperature in the range of 308 K to 358 K. The dielectric constant ( ɛ^' } ) and dielectric loss factor ( {tan} δ ) appeared to decrease with increasing frequency, while the alternating-current (AC) conductivity ( σ^' } ) increased. These dielectric parameters increased with increasing temperature. On the other hand, impedance spectroscopy gave Cole-Cole plots with only one semicircular arc for all the samples, indicating that the grain-boundary contribution was dominant in the conduction mechanism.

Noise and Ionic Conductivity in Glass Nanochannels

NASA Astrophysics Data System (ADS)

Wiener, Benjamin; Siria, Alessandro; Bocquet, Lydéric; Stein, Derek

2015-03-01

Ion transport in nanochannels is relevant to processes in biology and has technological applications like batteries, fuel cells, and water desalination. We report experimental studies of the ionic conductance and noise characteristics of pulled glass capillaries with openings on the order of 200 nanometers. We employed an AC measurement technique to probe very low frequency fluctuations in the conductivity and to test a theory attributing these to chemical fluctuations in the surface charge density of the glass. We also investigate Hooge's empirical description of the noise power spectrum and its relationship to current rectification observed in nanochannels in the surface dominated ``Dukhin'' regime. Finally, we test the effects of anion and cation mobility on the direction and magnitude of the observed rectification. Research supported by NSF Grant DMR-1409577 and Oxford Nanopore Technologies.

Spin supercurrent and effect of quantum phase transition in the two-dimensional XY model

NASA Astrophysics Data System (ADS)

Lima, L. S.

2018-04-01

We have verified the influence of quantum phase transition on spin transport in the spin-1 two-dimensional XY model on the square lattice, with easy plane, single ion and exchange anisotropy. We analyze the effect of the phase transition from the Néel phase to the paramagnetic phase on the AC spin conductivity. Our results show a bit influence of the quantum phase transition on the conductivity. We also obtain a conventional spin transport for ω > 0 and an ideal spin transport in the limit of DC conductivity and therefore, a superfluid spin transport for the DC current in this limit. We have made the diagrammatic expansion for the Green-function with objective to include the effect exciton-exciton scattering on the results.

The dynamical conductance of graphene tunnelling structures.

PubMed

Zhang, Huan; Chan, K S; Lin, Zijing

2011-12-16

The dynamical conductances of graphene tunnelling structures were numerically calculated using the scattering matrix method with the interaction effect included in a phenomenological approach. The overall single-barrier dynamical conductance is capacitative. Transmission resonances in the single-barrier structure lead to dips in the capacitative imaginary part of the response. This is different from the ac responses of typical semiconductor nanostructures, where transmission resonances usually lead to inductive peaks. The features of the dips depend on the Fermi energy. When the Fermi energy is below half of the barrier height, the dips are sharper. When the Fermi energy is higher than half of the barrier height, the dips are broader. Inductive behaviours can be observed in a double-barrier structure due to the resonances formed by reflection between the two barriers.

Mott glass from localization and confinement

NASA Astrophysics Data System (ADS)

Chou, Yang-Zhi; Nandkishore, Rahul M.; Radzihovsky, Leo

2018-05-01

We study a system of fermions in one spatial dimension with linearly confining interactions and short-range disorder. We focus on the zero-temperature properties of this system, which we characterize using bosonization and the Gaussian variational method. We compute the static compressibility and ac conductivity, and thereby demonstrate that the system is incompressible, but exhibits gapless optical conductivity. This corresponds to a "Mott glass" state, distinct from an Anderson and a fully gapped Mott insulator, arising due to the interplay of disorder and charge confinement. We argue that this Mott glass phenomenology should persist to nonzero temperatures.

Protonic Conductors for Intermediate Temperature Fuel Cell Electrolytes: Superprotonic CsH2PO4 Stabilization and in-Doped SnP2O7 Structure Study

NASA Astrophysics Data System (ADS)

Martinez Salinas, Heber Jair

Proton conductor solid electrolytes CsH2PO4 and In-doped tin pyrophosphate have been investigated as candidates to fill a gap of suitable electrolytes for fuel cells at the intermediate temperature range due their unusually high conductivities between 200 and 300 °C. Unfortunately, in the case of CsH2PO4, complicated experimental conditions, like a humidified environment, or high pressure, are needed to preserve the sought high conducting phase. In the first stage of this work, X-ray diffraction on CsH2PO 4 samples performed in air, and under normal conditions of humidity and pressure, evidence of the cubic phase of CsH2PO4 was observed during short intervals of temperature and time, starting at 215 °C and disappearing completely at 265 °C into a dehydrated phase. An AC impedance spectroscopy experimental setup has been assembled and data has been successfully collected on undoped, and doped CsH2PO 4 samples to investigate the effects of chemical and environmental modifications. Measurements performed in the temperature range 200 - 260 °C, and using the frequency range 1 - 6 MHz, showed that the high conducting phase of undoped CsH2PO4 was present for a very short interval of temperature. Additionally, these measurements showed that nano-silica-doped CsH2PO4, and CsH2PO4 under a humidified environment achieve the highest values of conductivity, above 10-2 S cm-1 among the samples tested. In the second stage of this investigation, AC impedance spectroscopy measurements were successfully performed on CsH2PO4 samples in air, at temperatures from 200 - 260 °C, and in the frequency range 1 - 6 MHz, inside a hermetically sealed stainless-steel chamber, which was designed and assembled in-house. Results showed that the highly conducting phase of CsH2PO 4 was achieved at temperatures measured above 230 °C, reaching conductivity values up to 1.7 x10-2 S cm-1, and remaining stable for over 40 hours. Consequent X-ray diffraction analysis of such samples showed that a monoclinic structure, characteristic of room temperature CsH 2PO4, was the only phase present even after the samples had been heated for over 40 hours at a temperature of 250 °C. By using this novel contraption, this has been the first time that undoped CsH2PO 4 has achieved its high conductivity phase and maintained a stable conductivity for a significant amount of time in air, without the use of a humidified environment, and without high pressure in an AC impedance spectroscopy study. Finally, in-house and synchrotron X-ray diffraction studies performed in the Sn1-xInxP2O7 series showed the cubic structure characteristic of the undoped compound at room temperature remains present up to temperatures of 250 °C. Sn0.9In 0.1P2O7, which is known to have the highest conductivity of the compound series, presented an increased unit cell as compared to the rest of the series when measured in air. However, the increased unit cell was not observed when measured under vacuum or an inert gas. Doping did not produce any major distortions on the P2O7 tetrahedra.

A novel alternating current multiple array electrothermal micropump for lab-on-a-chip applications.

PubMed

Salari, A; Navi, M; Dalton, C

2015-01-01

The AC electrothermal technique is very promising for biofluid micropumping, due to its ability to pump high conductivity fluids. However, compared to electroosmotic micropumps, a lack of high fluid flow is a disadvantage. In this paper, a novel AC multiple array electrothermal (MAET) micropump, utilizing multiple microelectrode arrays placed on the side-walls of the fluidic channel of the micropump, is introduced. Asymmetric coplanar microelectrodes are placed on all sides of the microfluidic channel, and are actuated in different phases: one, two opposing, two adjacent, three, or all sides at the same time. Micropumps with different combinations of side electrodes and cross sections are numerically investigated in this paper. The effect of the governing parameters with respect to thermal, fluidic, and electrical properties are studied and discussed. To verify the simulations, the AC MAET concept was then fabricated and experimentally tested. The resulted fluid flow achieved by the experiments showed good agreement with the corresponding simulations. The number of side electrode arrays and the actuation patterns were also found to greatly influence the micropump performance. This study shows that the new multiple array electrothermal micropump design can be used in a wide range of applications such as drug delivery and lab-on-a-chip, where high flow rate and high precision micropumping devices for high conductivity fluids are needed.

Effect of substitution group on dielectric properties of 4H-pyrano [3, 2-c] quinoline derivatives thin films

NASA Astrophysics Data System (ADS)

H, M. Zeyada; F, M. El-Taweel; M, M. El-Nahass; M, M. El-Shabaan

2016-07-01

The AC electrical conductivity and dielectrical properties of 2-amino-6-ethyl-5-oxo-4-(3-phenoxyphenyl)-5,6-dihydro-4H-pyrano[3, 2-c]quinoline-3-carbonitrile (Ph-HPQ) and 2-amino-4-(2-chlorophenyl)-6-ethyl-5-oxo-5,6-dihydro-4H-pyrano [3, 2-c] quinoline-3-carbonitrile (Ch-HPQ) thin films were determined in the frequency range of 0.5 kHz-5 MHz and the temperature range of 290-443 K. The AC electrical conduction of both compounds in thin film form is governed by the correlated barrier hopping (CBH) mechanism. Some parameters such as the barrier height, the maximum barrier height, the density of charges, and the hopping distance were determined as functions of temperature and frequency. The phenoxyphenyl group has a greater influence on those parameters than the chlorophenyl group. The AC activation energies were determined at different frequencies and temperatures. The dielectric behaviors of Ph-HPQ and Ch-HPQ were investigated using the impedance spectroscopy technique. The impedance data are presented in Nyquist diagrams for different temperatures. The Ch-HPQ films have higher impedance than the Ph-HPQ films. The real dielectric constant and dielectric loss show a remarkable dependence on the frequency and temperature. The Ph-HPQ has higher dielectric constants than the Ch-HPQ.

Indoor thermal environment of bedroom during sleep in Malaysia

NASA Astrophysics Data System (ADS)

Tsuzuki, Kazuyo; Mori, Ikue

2017-10-01

This study was conducted to investigate the indoor thermal environment and sleep of occupants in bedrooms where air conditioners (ACs) are preferentially installed. Field measurements and questionnaires were conducted for 22 houses, with a total of 28 occupants, located in the suburbs of Kuala Lumpur. The participants were requested to wear a wrist actigraphy on the non-dominant hand for three consecutive days, except while bathing or washing hands in order to evaluate sleep by the activity of the actigraphy. The average air temperatures in the bedrooms were 22.6-28.9 °C and 28.1-32.2 °C with and without AC, respectively. The observed lowest air temperature was below 21 °C in a bedroom with AC. Such low air temperatures are not considered appropriate in terms of energy consumption and the occupants' physiological condition during sleep. The wind velocity of fresh air coming through the open window was found as well as when the use of a fan. From the relations among the factors of thermal environment, increased wind velocity seems to compensate for increased air temperature and increased relative humidity. The sleep efficiency index (SEI) looks decreased in accordance with increased air temperature, increased air velocity, and increased relative humidity. However, no statistical significances were found in those relationships. New effective temperature (SET*) was calculated from measured thermal factors and relation was examined with SEI.

Effect of chromium substitution on the dielectric properties of mixed Ni-Zn ferrite prepared by WOWS sol–gel technique

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ashtar, M.; Munir, A.; Anis-ur-Rehman, M.

2016-07-15

Graphical abstract: Variation of AC conductivity (σ{sub AC}) as a function of natural log of angular frequency (lnω) for Ni{sub 0.5}Zn{sub 0.5}Fe{sub 2-x}Cr{sub x}O{sub 4} nanoferrites at room temperature. - Highlights: • Cr doped mixed Ni-Zn ferrites were successfully synthesized by a newly developed WOWS sol gel technique. • The specific surface area and specific surface area to volume ratio increased with decrease in particle size. • The resonance peaks appeared in dielectric loss graphs, shifting towards low frequency with the increase in Cr concentration. • The prepared samples have the lowest values of the dielectric constant. • The dielectricmore » constant were observed to be inversely proportional to square root of the AC resistivity. - Abstract: Cr{sup +3} doped Ni-Zn nanoferrite samples with composition Ni{sub 0.5}Zn{sub 0.5}Fe{sub 2-x}Cr{sub x}O{sub 4}(x = 0.1, 0.2, 0.3, 0.4) were synthesized With Out Water and Surfactant (WOWS) sol-gel technique. The structural, morphological and dielectric properties of the samples were investigated. The lattice constant, crystallite size, theoretical density and porosity of each sample were obtained from X-ray diffraction (XRD) data. The specific surface area and specific surface area to volume ratio increased with the decrease in the size of Cr{sup +3} doped Ni-Zn ferrite nanoparticles, as the concentration of Cr{sup +3} increased. The SEM analysis revealed that the particles were of nano size and of spherical shape. The dielectric parameters such as dielectric constant (ε′) and dielectric loss (tanδ) of all the samples as a function of frequency at room temperature were measured. The AC conductivity (σ{sub AC}) was determined from the dielectric parameters, which showed increasing trend with the rise in frequency.« less

Radio frequency abnormal dielectric response of manganese chromite (MnCr{sub 2}O{sub 4}) nanoparticles synthesized by coprecipitation method

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gul, Muhammad, E-mail: mgul@upesh.edu.pk

2016-04-15

Highlights: • Uniform MnCr{sub 2}O{sub 4} nanoparticles synthesized by surfactant-free coprecipitation route. • XRD analysis confirmed the single spinel phase formation in the material. • Dielectric loss was found abnormal over certain lower frequencies. • AC conductivity proved the involvement of small polarons in conduction process. - Abstract: Radio frequency dielectric behavior of nanocrystalline MnCr{sub 2}O{sub 4} synthesized via surfactant-free controlled coprecipitation route has been studied. Keeping in view the necessity of particle size uniformity and phase purity for genuine performance, experimental conditions were optimized accordingly. The scanning electron micrographs of the synthesized product revealed the formation of monodispersed particlemore » system. X-ray diffraction analysis confirmed monophasic spinel structure formation with 65 nm crystallite size. Two characteristic peaks observed between 700 cm{sup −1} and 400 cm{sup −1} in the FTIR spectrum also supported the spinel phase purity of compound. The dielectric constant was found normal, but loss tangent of the sample showed abnormal behavior with frequency. The observed dielectric behavior of the synthesized product has been explained on the basis of space-charge polarization according to Maxwell–Wagner’s model and mutual contribution of n-type &p-type charge carriers (Rezlescu model). The ac conductivity linearly increased with frequency highlighting the existence of polaron hopping.« less

Metamaterial Behavior of Polymer Nanocomposites Based on Polypropylene/Multi-Walled Carbon Nanotubes Fabricated by Means of Ultrasound-Assisted Extrusion

PubMed Central

Pérez-Medina, Juan C.; Waldo-Mendoza, Miguel A.; Cruz-Delgado, Víctor J.; Quiñones-Jurado, Zoe V.; González-Morones, Pablo; Ziolo, Ronald F.; Martínez-Colunga, Juan G.; Soriano-Corral, Florentino; Avila-Orta, Carlos A.

2016-01-01

Metamaterial behavior of polymer nanocomposites (NCs) based on isotactic polypropylene (iPP) and multi-walled carbon nanotubes (MWCNTs) was investigated based on the observation of a negative dielectric constant (ε′). It is demonstrated that as the dielectric constant switches from negative to positive, the plasma frequency (ωp) depends strongly on the ultrasound-assisted fabrication method, as well as on the melt flow index of the iPP. NCs were fabricated using ultrasound-assisted extrusion methods with 10 wt % loadings of MWCNTs in iPPs with different melt flow indices (MFI). AC electrical conductivity (σ(AC)) as a function of frequency was determined to complement the electrical classification of the NCs, which were previously designated as insulating (I), static-dissipative (SD), and conductive (C) materials. It was found that the SD and C materials can also be classified as metamaterials (M). This type of behavior emerges from the negative dielectric constant observed at low frequencies although, at certain frequencies, the dielectric constant becomes positive. Our method of fabrication allows for the preparation of metamaterials with tunable ωp. iPP pure samples show only positive dielectric constants. Electrical conductivity increases in all cases with the addition of MWCNTs with the largest increases observed for samples with the highest MFI. A relationship between MFI and the fabrication method, with respect to electrical properties, is reported. PMID:28774042

Temperature dependent dielectric relaxation and ac-conductivity of alkali niobate ceramics studied by impedance spectroscopy

NASA Astrophysics Data System (ADS)

Yadav, Abhinav; Mantry, Snigdha Paramita; Fahad, Mohd.; Sarun, P. M.

2018-05-01

Sodium niobate (NaNbO3) ceramics is prepared by conventional solid state reaction method at sintering temperature 1150 °C for 4 h. The structural information of the material has been investigated by X-ray diffraction (XRD) and Field emission scanning electron microscopy (FE-SEM). The XRD analysis of NaNbO3 ceramics shows an orthorhombic structure. The FE-SEM micrograph of NaNbO3 ceramics exhibit grains with grain sizes ranging between 1 μm to 5 μm. The surface coverage and average grain size of NaNbO3 ceramics are found to be 97.6 % and 2.5 μm, respectively. Frequency dependent electrical properties of NaNbO3 is investigated from room temperature to 500 °C in wide frequency range (100 Hz-5 MHz). Dielectric constant, ac-conductivity, impedance, modulus and Nyquist analysis are performed. The observed dielectric constant (1 kHz) at transition temperature (400 °C) are 975. From conductivity analysis, the estimated activation energy of NaNbO3 ceramics is 0.58 eV at 10 kHz. The result of Nyquist plot shows that the electrical behavior of NaNbO3 ceramics is contributed by grain and grain boundary responses. The impedance and modulus spectrum asserts that the negative temperature coefficient of resistance (NTCR) behavior and non-Debye type relaxation in NaNbO3.

Influence of stress on the structural and dielectric properties of rf magnetron sputtered zinc oxide thin film

NASA Astrophysics Data System (ADS)

Menon, Rashmi; Sreenivas, K.; Gupta, Vinay

2008-05-01

Highly c axis oriented zinc oxide (ZnO) thin films have been prepared on 1737 Corning glass substrate by planar rf magnetron sputtering under varying pressure (10-50mTorr) and different oxygen percentage (40%-100%) in reactive gas mixtures. The as-grown ZnO thin films were found to have stress over a wide range from -6×1010to-9×107dynes/cm2. The presence of stress depends strongly on processing conditions, and films become almost stress free under a unique combination of sputtering pressure and reactive gas composition. The studies show a correlation of stress with structural and electrical properties of the ZnO thin film. The stressed films possess high electrical conductivity and exhibits strong dielectric dispersion over a wide frequency (1kHz-1MHz). The dielectric constant ɛ'(ω) of stress free ZnO film was almost frequency independent and was close to the bulk value. The measured value of dc conductivity, σdc(ω) and ac conductivity σac(ω) of stress free ZnO film was 1.3×10-9 and 6.8×10-5Ω-1cm-1, respectively. The observed variation in the structural and electrical properties of ZnO thin film with stress has been analyzed in the light of growth kinetics.

Transient Hypothyroidism During Lactation Arrests Myelination in the Anterior Commissure of Rats. A Magnetic Resonance Image and Electron Microscope Study.

PubMed

Lucia, Federico S; Pacheco-Torres, Jesús; González-Granero, Susana; Canals, Santiago; Obregón, María-Jesús; García-Verdugo, José M; Berbel, Pere

2018-01-01

Thyroid hormone deficiency at early postnatal ages affects the cytoarchitecture and function of neocortical and telencephalic limbic areas, leading to impaired associative memory and in a wide spectrum of neurological and mental diseases. Neocortical areas project interhemispheric axons mostly through the corpus callosum and to a lesser extent through the anterior commissure (AC), while limbic areas mostly project through the AC and hippocampal commissures. Functional magnetic resonance data from children with late diagnosed congenital hypothyroidism and abnormal verbal memory processing, suggest altered ipsilateral and contralateral telencephalic connections. Gestational hypothyroidism affects AC development but the possible effect of transient and chronic postnatal hypothyroidism, as occurs in late diagnosed neonates with congenital hypothyroidism and in children growing up in iodine deficient areas, still remains unknown. We studied AC development using in vivo magnetic resonance imaging and electron microscopy in hypothyroid and control male rats. Four groups of methimazole (MMI) treated rats were studied. One group was MMI-treated from postnatal day (P) 0 to P21; some of these rats were also treated with L-thyroxine (T4) from P15 to P21, as a model for early transient hypothyroidism. Other rats were MMI-treated from P0 to P150 and from embryonic day (E) 10 to P170, as a chronic hypothyroidism group. The results were compared with age paired control rats. The normalized T2 signal using magnetic resonance image was higher in MMI-treated rats and correlated with the number and percentage of myelinated axons. Using electron microscopy, we observed decreased myelinated axon number and density in transient and chronic hypothyroid rats at P150, unmyelinated axon number increased slightly in chronic hypothyroid rats. In MMI-treated rats, the myelinated axon g-ratio and conduction velocity was similar to control rats, but with a decrease in conduction delays. These data show that early postnatal transient and chronic hypothyroidism alters AC maturation that may affect the transfer of information through the AC. The alterations cannot be recovered after delayed T4-treatment. Our data support the neurocognitive delay found in late T4-treated children with congenital hypothyroidism.

Epidemiological characteristics, management and early outcomes of acute coronary syndromes in Greece: The PHAETHON study.

PubMed

Andrikopoulos, G; Terentes-Printzios, D; Tzeis, S; Vlachopoulos, C; Varounis, C; Nikas, N; Lekakis, J; Stakos, D; Lymperi, S; Symeonidis, D; Chrissos, D; Kyrpizidis, C; Alexopoulos, D; Zombolos, S; Foussas, S; Κranidis, Α; Oikonomou, Κ; Vasilikos, V; Andronikos, P; Dermitzakis, Α; Richter, D; Fragakis, N; Styliadis, I; Mavridis, S; Stefanadis, C; Vardas, P

In view of recent therapeutic breakthroughs in acute coronary syndromes (ACS) and essential demographic and socioeconomic changes in Greece, we conducted the prospective, multi-center, nationwide PHAETHON study (An Epidemiological Cohort Study of Acute Coronary Syndromes in the Greek Population) that aimed to recruit a representative cohort of ACS patients and examine current management practices and patient prognosis. The PHAETHON study was conducted from May 2012 to February 2014. We enrolled 800 consecutive ACS patients from 37 hospitals with a proportional representation of all types of hospitals and geographical areas. Patients were followed for a median period of 189 days. Outcome was assessed with a composite endpoint of death, myocardial infarction, stroke, urgent revascularization and urgent hospitalization for cardiovascular causes. The mean age of patients was 62.7 years (78% males). The majority of patients (n=411, 51%) presented with ST-elevation myocardial infarction (STEMI), whereas 389 patients presented with NSTEMI (n=303, 38%) or UA (n=86, 11%). Overall, 58.8% of the patients had hypertension, 26.5% were diabetic, 52.5% had dyslipidemia, 71.1% had a smoking history (current or past), 25.8% had a family history of coronary artery disease (CAD) and 24.1% had a prior history of CAD. In STEMI patients, 44.5% of patients were treated with thrombolysis, 38.9% underwent a coronary angiogram (34.1% were treated with primary percutaneous coronary intervention) and 16.5% did not receive urgent treatment. The pain-to-door time was 169 minutes. During hospitalization, 301 (38%) patients presented one or more complications, and 13 died (1.6%). During follow-up, 99 (12.6%) patients experienced the composite endpoint, and 21 died (2.7%). The PHAETHON study provided valuable insights into the epidemiology, management and outcome of ACS patients in Greece. Management of ACS resembles the management observed in other European countries. However, several issues still to be addressed by public authorities for the timely and proper management of ACS. Copyright © 2016 Hellenic Cardiological Society. Published by Elsevier B.V. All rights reserved.

Electrical modulus analysis on the Ni/CCTO/PVDF system near the percolation threshold

NASA Astrophysics Data System (ADS)

Yang, Wenhu; Yu, Shuhui; Sun, Rong; Ke, Shanming; Huang, Haitao; Du, Ruxu

2011-11-01

A type of Ni/CCTO/PVDF three-phase percolative composite was prepared, in which the filler content (volume fraction) of Ni and CCTO was set at 60 vol%. The dependence of permittivity, electrical modulus and ac conductivity on the concentration of Ni and CCTO fillers near the percolation threshold was investigated in detail. The permittivity of the composites dramatically increased as the Ni content approached 24 vol%. This unique physical mechanism was realized as the formation of conductive channels near the percolation threshold. Analysis on the electrical modulus showed that the conductive channels are governed by three relaxation processes induced by the fillers (Ni, CCTO) and PVDF matrix, which are the interfacial polarization derived from the interfaces between fillers (Ni, CCTO) and PVDF matrix, and the polarization of CCTO ceramic filler and PVDF matrix. The conductivity behaviour with various Ni loadings and temperature suggested that the transition from an insulating to a conducting state should be induced by charge tunnelling between Ni-Ni particles, Ni-CCTO fillers and Ni-PVDF matrix. These findings demonstrated that the tunnelling conduction in the composite can be attributed to the unique physical mechanism near the percolation threshold.

Promising efficacy of novel BTK inhibitor AC0010 in mantle cell lymphoma.

PubMed

Yan, Xiao; Zhou, Yile; Huang, Shujuan; Li, Xia; Yu, Mengxia; Huang, Jiansong; Wang, Jinghan; Ma, Zhixin; Jin, Jingrui; Pan, Jiajia; Li, Chenying; Li, Fenglin; Jin, Jie

2018-04-01

We researched into the effect and mechanism of AC0010, a novel BTK inhibitor, in MCL, and compared its efficacy and safety with Ibrutinib to develop a preclinical study for the future therapy of MCL. MTS assay was used to detect the growth inhibition caused by AC0010 and Ibrutinib, respectively, in MCL cell lines (Jeko-1 and JVM-2), primary MCL cells, and normal peripheral lymphocytes. Apoptosis of Jeko-1 and JVM-2 after exposure into AC0010 and Ibrutinib was conducted by flow cytometry; the expression of apoptosis-related proteins was checked by Western blot. q-PCR and Western blot were applied to examine the expression of BTK and p-BTK at mRNA and protein level as well as the BTK-ralated signaling pathways. MCL xenograft was developed to testify the efficacy and safety of AC0010 in vivo. In contrast with Ibrutinib, AC0010 proved to be more toxic to MCL cells in vitro (p < 0.01) with no augment in cytotoxicity to normal peripheral lymphocytes, and it can induce obvious apoptosis in MCL cell lines (p < 0.01) through caspase family and Bcl-2 family. AC0010 at 300 mg/kg can prolong the survival rate in MCL xenograft (p < 0.01). The phosphorylation of BTK is inhibited by AC0010 following simultaneously inhibition of BCR-BTK and PI3K/AKT signaling pathway in MCL cells. AC0010 is a novel BTK inhibitor of great efficacy and safety in MCL.

Effect of pH on the electrical properties and conducting mechanism of SnO2 nanoparticles

NASA Astrophysics Data System (ADS)

Periathai, R. Sudha; Abarna, S.; Hirankumar, G.; Jeyakumaran, N.; Prithivikumaran, N.

2017-03-01

Semiconductor nanoparticles have attracted more interests because of their size-dependent optical and electrical properties.SnO2 is an oxygen-deficient n-type semiconductor with a wide band gap of 3.6 eV (300 K). It has many remarkable applications as sensors, catalysts, transparent conducting electrodes, anode material for rechargeable Li- ion batteries and optoelectronic devices. In the present work, the role of pH in determining the electrical and dielectric properties of SnO2 nanoparticles has been studied as a function of temperature ranging from Room temperature (RT) to 114 °C in the frequency range of 7 MHz to 50 mHz using impedance spectroscopic technique. The non linear behavior observed in the thermal dependence of the conductance of SnO2 nanoparticles is explained by means of the surface property of SnO2 nanoparticles where proton hopping mechanism is dealt with. Jonscher's power law has been fitted for the conductance spectra and the frequency exponent ("s" value) gives an insight about the ac conducting mechanism. The temperature dependence of electrical relaxation phenomenon in the material has been observed. The complex electric modulus analysis indicates the possibility of hopping conduction mechanism in the system with non-exponential type of conductivity relaxation.

The origin of current blocking in interfacial conduction in Sr-doped lanthanum gallates

NASA Astrophysics Data System (ADS)

Park, Hee Jung

2018-02-01

The grain boundary transport of lanthanum gallate has been studied with various doping concentrations, and the origins of blocking on the grain boundary are compared. La1-xSrxGaO3 samples (x = 0.005, 0.01, 0.05 and 0.1) have been prepared and their bulk (grain) and grain boundary resistances been experimentally measured as a function of temperature (T: 200-550 °C) and oxygen partial pressure (Po2) using ac-impedance measurements. In addition, Hebb-Wagner polarization measurements have been conducted to investigate the electrical conductivity of minor charge carriers in the lanthanum gallates. The grain boundary resistance in the low-doped materials (x = 0.005 and 0.01) increases with increasing Po2 while in the highly-doped materials (x = 0.05, 0.1) it hardly depended on Po2. At lower concentrations conduction is mixed and at higher concentrations is found to be predominantly ionic conductivity. The space charge model successfully describes the mixed conduction at the grain boundary at low-doping, but does not explain the predominant ionic conductivity at high-doping. The origin of blocking at high-doping is explained by the crystallographic asymmetry of the grain boundary with respect to the bulk and/or Sr-segregation.

Impedance Spectroscopy Analysis of Mg4Nb2O9 Ceramics with Different Additions of V2O5 for Microwave and Radio Frequency Applications

NASA Astrophysics Data System (ADS)

Filho, J. M. S.; Rodrigues Junior, C. A.; Sousa, D. G.; Oliveira, R. G. M.; Costa, M. M.; Barroso, G. C.; Sombra, A. S. B.

2017-07-01

The complex impedance spectroscopy study of magnesium niobate Mg4Nb2O9 (MN) ceramics with different additions of V2O5 (0%, 2%, 5%) was performed in this present paper. The preparation of MN samples were carried out by using the solid-state reaction method with a high-energy milling machine. Frequency and temperature dependence of the complex impedance, complex modulus analysis, and conductivity were measured and calculated at different temperatures by using a network impedance analyzer. A non-Debye type relaxation was observed showing a decentralization of the semicircles. Cole-Cole formalism was adopted here with the help of a computer program used to fit the experimental data. A typical universal dielectric response in the frequency-dependent conductivity at different temperatures was found. The frequency dependent ac conductivity at different temperatures indicates that the conduction process is thermally activated. The activation energy was obtained from the Arrhenius fitting by using conductivity and electrical modules data. The results would help to understand deeply the relaxation process in these types of materials.

Solution-Based Electro-Orientation Spectroscopy (EOS) for Contactless Measurement of Semiconductor Nanowires

NASA Astrophysics Data System (ADS)

Yuan, Wuhan; Mohabir, Amar; Tutuncuoglu, Gozde; Filler, Michael; Feldman, Leonard; Shan, Jerry

2017-11-01

Solution-based, contactless methods for determining the electrical conductivity of nanowires and nanotubes have unique advantages over conventional techniques in terms of high throughput and compatibility with further solution-based processing and assembly methods. Here, we describe the solution-based electro-orientation spectroscopy (EOS) method, in which nanowire conductivity is measured from the AC-electric-field-induced alignment rate of the nanowire in a suspending fluid. The particle conductivity is determined from the measured crossover frequency between conductivity-dominated, low-frequency alignment to the permittivity-dominated, high-frequency regime. We discuss the extension of the EOS measurement range by an order-of-magnitude, taking advantage of the high dielectric constant of deionized water. With water and other fluids, we demonstrate that EOS can quantitatively characterize the electrical conductivities of nanowires over a 7-order-of-magnitude range, 10-5 to 102 S/m. We highlight the efficiency and utility of EOS for nanomaterial characterization by statistically characterizing the variability of semiconductor nanowires of the same nominal composition, and studying the connection between synthesis parameters and properties. NSF CBET-1604931.

Systematic Experimental and Computational Investigation of Ion Transport in Novel Polyether Electrolytes

NASA Astrophysics Data System (ADS)

Pesko, Danielle; Webb, Michael; Jung, Yukyung; Zheng, Qi; Miller, Thomas, III; Coates, Geoffrey; Balsara, Nitash

Polyethers, such as poly(ethylene oxide) (PEO), are considered to be the most promising polymer electrolyte materials due to their high ionic conductivity and electrochemical stability, both essential for battery applications. To gain a fundamental understanding of the transport properties of polyether systems, we design a systematic set of linear PEO-like polymers to explore the effect of adding carbon spacers to the backbone of the chain. Ac impedance spectroscopy is employed to measure the ionic conductivity of polyether/lithium salt electrolytes; the results elucidate tradeoffs between lowering the glass transition temperature and diluting the polar groups on the polymer chain. Molecular-level insight is provided by molecular dynamics simulations of the polyether electrolytes. We define the useful and intuitive metric of ``connectivity'', a parameter calculated from simulations which describes the physical arrangements of solvation sites in a polymer melt. Direct comparison of experiment and theory allows us to determine the relationship between connectivity and conductivity. The comparison provides insight regarding the factors that control conductivity, and highlights considerations that must be taken when designing new ion-conducting polymers.

First-principles investigations of ionic conduction in Li and Na borohydrides

NASA Astrophysics Data System (ADS)

Varley, Joel; Heo, Tae-Wook; Ray, Keith; Bonev, Stanimir; Wood, Brandon

Recent experimental studies have identified a family of alkali borohydride materials that exhibit superionic transition temperatures approaching room temperature and ionic conductivities exceeding 0.1 S/cm-1, making them highly promising solid electrolytes for next-generation batteries. Despite the rapid advances in improving the superionic conductivity in these materials, an understanding of the exact mechanisms driving the transport remains unknown. Here we use ab initio molecular dynamics calculations to address this issue by characterizing the diffusivity of the Li and Na species in a representative set of closoborane ionic conductors. We investigate both the Na and Li-containing borohydrides with icosahedral (B12H12) and double-capped square antiprism (B10H10) anion species and discuss the trends in ionic conductivity as a function of stoichiometry and the incorporation of various dopants. Our results support the borohydrides as a subset of a larger family of very promising solid electrolytes and identify strategies to improving the conductivity in these materials. This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

Use of emergency medical services in the second gulf registry of acute coronary events.

PubMed

AlHabib, Khalid F; Alfaleh, Hussam; Hersi, Ahmad; Kashour, Tarek; Alsheikh-Ali, Alawi A; Suwaidi, Jassim Al; Sulaiman, Kadhim; Saif, Shukri Al; Almahmeed, Wael; Asaad, Nidal; Amin, Haitham; Al-Motarreb, Ahmed; Thalib, Lukman

2014-09-01

Data are scarce regarding emergency medical service (EMS) usage by patients with acute coronary syndrome (ACS) in the Arabian Gulf region. This 9-month in-hospital prospective ACS registry was conducted in Arabian Gulf countries, with 30-day and 1-year follow-up mortality rates. Of 5184 patients with ACS, 1293 (25%) arrived at the hospital by EMS. The EMS group (vs non-EMS) was more likely to be male, have cardiac arrest on presentation, be current or exsmokers, and have moderate or severe left ventricular dysfunction and ST-segment elevation myocardial infarction (STEMI). The EMS group had higher crude mortality rates during hospitalization and after hospital discharge but not after adjustment for clinical factors and treatments. The EMSs are underused in the Arabian Gulf region. Short- and long-term mortality rates in patients with ACS are similar between those who used and did not use EMS. Quality improvement in the EMS infrastructure and establishment of integrated STEMI networks are urgently needed. © The Author(s) 2013.

Charge carrier dynamics and relaxation in (polyethylene oxide-lithium-salt)-based polymer electrolyte containing 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide as ionic liquid

NASA Astrophysics Data System (ADS)

Karmakar, A.; Ghosh, A.

2011-11-01

In this paper we report the dynamics of charge carriers and relaxation in polymer electrolytes based on polyethylene oxide (PEO), lithium bis(trifluoromethylsulfonyl)imide (LiTFSI) and 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide (BMPTFSI) ionic liquid prepared by solution cast technique. It has been observed that the incorporation of BMPTFSI into PEO-LiTFSI electrolyte is an effective way for increasing the amorphous phase to a large extent. It has also been observed that both the glass transition and melting temperatures decrease with the increase of BMPTFSI concentration. The ionic conductivity of these polymer electrolytes increases with the increase of BMPTFSI concentration. The highest ionic conductivity obtained at 25 °C is ˜3×10-4 S cm-1 for the electrolyte containing 60 wt % BMPTFSI and ethylene oxide (EO)/Li ratio of 20. The temperature dependence of the dc conductivity and the hopping frequency show Vogel-Tamman-Fulcher type behavior indicating a strong coupling between the ionic and the polymer chain segmental motions. The frequency dependence of the ac conductivity exhibits a power law with an exponent n which decreases with the increase of temperature. The scaling of the ac conductivity indicates that relaxation dynamics of charge carriers follows a common mechanism for all temperatures and BMPTFSI concentrations. We have also presented the electric modulus data which have been analyzed in the framework of a Havriliak-Negami equation and the shape parameters obtained by the analysis show slight temperature dependence, but change sharply with BMPTFSI concentration. The stretched exponent β obtained from Kohlrausch-Williams-Watts fit to the modulus data is much lower than unity signifying that the relaxation is highly nonexponential. The decay function obtained from analysis of experimental modulus data is highly asymmetric with time.

Design and evaluation of 66 kV-class HTS power cable using REBCO wires

NASA Astrophysics Data System (ADS)

Ohya, M.; Yumura, H.; Masuda, T.; Amemiya, N.; Ishiyama, A.; Ohkuma, T.

2011-11-01

Sumitomo Electric (SEI) has been involved in the development of 66 kV-class HTS cables using REBCO wires. One of the technical targets in this project is to reduce the AC loss to less than 2 W/m/phase at 5 kA. SEI has developed a clad-type of textured metal substrate with lower magnetization loss compared with a conventional NiW substrate. In addition, 30 mm-wide REBCO tapes were slit into 4 mm-wide strips, and these strips were wound spirally on a former with small gaps. The AC loss of a manufactured 4-layer cable conductor was 1.5 W/m at 5 kA at 64 K. Given that the AC loss in a shield layer is supposed to be one-fourth of a whole cable core loss, our cables are expected to achieve the AC loss target of less than 2 W/m/phase at 5 kA. Another important target is to manage a fault current. A cable core was designed and fabricated based on the simulation findings, and over-current tests (max. 31.5 kA, 2 s) were conducted to check its performance. The critical current value of the cable cores were measured before and after the over-current tests and verified its soundness. A 5 kA-class current lead for the cable terminations was also developed. The current loading tests were conducted for the developed current leads. The temperature distribution of the current leads reached to the steady-state within less than 12 h, and it was confirmed that the developed current lead has enough capacity of 5 kA loading.

The role of prasugrel in the management of acute coronary syndromes: a systematic review.

PubMed

Spartalis, M; Tzatzaki, E; Spartalis, E; Damaskos, C; Athanasiou, A; Moris, D; Politou, M

2017-10-01

Dual antiplatelet therapy (DAPT) is the treatment of choice in the medical management of patients with acute coronary syndrome (ACS). The combination of aspirin and a P2Y12 inhibitor in patients who receive a coronary stent reduces the rate of stent thrombosis and the rates of major adverse cardiovascular events. However, patients with acute coronary syndrome remain at risk of recurrent cardiovascular events despite the advance of medical therapy. The limitations of clopidogrel with variable antiplatelet effects and delayed onset of action are well established and lead to the development of newer P2Y12 inhibitors. Prasugrel is a selective adenosine diphosphate (ADP) receptor antagonist indicated for use in patients with ACS. Prasugrel provides greater inhibition of platelet aggregation than clopidogrel and has a rapid onset of action. We have conducted a systematic review to retrieve current evidence regarding the role of prasugrel in the management of ACS. Evidence comparing prasugrel, clopidogrel, and ticagrelor remain scant. A complete literature survey was performed using PubMed database search to gather available information regarding management of acute coronary syndromes and prasugrel. An explorative comparison of the safety and efficacy of prasugrel, clopidogrel, and ticagrelor was also conducted. Prasugrel and ticagrelor are more efficacious than clopidogrel in reducing the occurrence of non-fatal myocardial infarction, stroke, or cardiovascular (CV) death but they have also an increased risk of major bleeding in comparison to clopidogrel. Prasugrel and ticagrelor are today the recommended first-line agents in patients with ACS. The estimation of which drug is superior over the other cannot be reliably established from the current trials.

AC electrothermal technique in microchannels

NASA Astrophysics Data System (ADS)

Salari, Alinaghi; Navi, Maryam; Dalton, Colin

2017-02-01

Electrokinetic techniques have a wide range of applications in droplet, particle, and fluid manipulation systems. In general, they can be categorized into different subgroups including electroosmosis, electrothermal, electrophoresis, dielectrophoresis, etc. The AC electrothermal (ACET) technique has been shown to be very effective in applications which involve high conductivity fluids, such as blood, which are typically used in biomedical applications. In the past few years, the ACET effect has received considerable attention. Unlike AC electroosmosis (ACEO), the ACET effect shows plateaus in force in a wide frequency range. In other words, with electrothermal force, velocity is more steady and predictable at different frequencies, compared to ACEO and dielectrophoresis (DEP). Although electrothermal microflows form as a result of Joule heating in the fluid, due to high conduction of heat to the ambience, the temperature rise in the fluid is not so high as to threaten the nature of the biofluids. The average temperature rise resulting from the ACET effect is below 5 °K. In order to generate high strength AC electric fields, microfabricated electrode arrays are commonly used in microchannels. For pumping applications, it is essential to create asymmetry in the electric field, typically by having asymmetrical electrode pairs. There is no defined border between many electrokinetic techniques, and as such the point where electrothermal processes interferes with other electrokinetic techniques is not clear in the literature. In addition, there have been comprehensive reviews on micropumps, electrokinetics, and their subcategories, but the literature lacks a detailed up-to-date review on electrothermal microdevices. In this paper, a brief review is made specifically on electric fields in ACET devices, in order to provide an insight for the reader about the importance of this aspect of ACET devices and the improvements made to date.

Lithium1.3Aluminum0.3Titanium1.7Phosphate as a solid state Li-ion conductor: Issues with microcracking and stability in aqueous solutions

NASA Astrophysics Data System (ADS)

Jackman, Spencer D.

Lithium aluminum titanium phosphate (LATP) with formula Li1.3Al0.3Ti1.7(PO4)3 was analyzed and tested to better understand its applicability as a solid state ion conducting ceramic material for electrochemical applications. Sintered samples were obtained from Ceramatec, Inc. in Salt Lake City and characterized in terms of density, phase-purity, fracture toughness, Young's modulus, thermal expansion behavior, mechanical strength, a.c. and d.c. ionic conductivity, and susceptibility to static and electrochemical corrosion in aqueous Li salt solutions. It was shown that LATP is prone to microcrack generation because of high thermal expansion anisotropy. A.c. impedance spectra of high-purity LATP of varying grain sizes showed that microcracking had a negative impact on the ionic conduction of Li along grain boundaries, with fine-grained (1.7±0.7 µm) LATP having twice the ionic conductivity of the same purity of coarse-grained (4.8±1.9 µm) LATP at 50°C. LATP with detectible secondary phases had lower ionic conductivity for similar grain sizes, as would be expected. The Young's modulus of fine-grained LATP was measured to be 115 GPa, and the highest biaxial strength was 191±11 MPa when tested in mineral oil, 144±13 MPa as measured in air, and 26±7 MPa after exposure to deionized water, suggesting that LATP undergoes stress-corrosion cracking. After exposure to LiOH, the strength was 76±19 MPa. This decrease in strength was observed despite there being no measureable change in a.c. impedance spectra, X-ray diffraction, or sample mass, suggesting phosphate glasses at grain boundaries. The chemical and electrochemical stability of high-purity LATP in aqueous electrochemical cells was evaluated using LiOH, LiCl, LiNO3, and LiCOOCH3 salts as the Li source. LATP was found to be most stable between pH 8-9, with the longest cell operating continuously at 25 mA cm-2 for 625 hours at 40°C in LiCOOCH3. At pH values outside of the 7-10 range, eventual membrane degradation was observed in all aqueous systems under electrochemical conditions. While LATP was surprisingly resistant to static corrosion in a hot, aqueous LiOH solution, electrochemical degradation was observed at the cathode due to subsurface pitting. Strength measurements were more instructive than impedance measurements in detecting this degradation.

Solid electrolytes for fluoride ion batteries: ionic conductivity in polycrystalline tysonite-type fluorides.

PubMed

Rongeat, Carine; Reddy, M Anji; Witter, Raiker; Fichtner, Maximilian

2014-02-12

Batteries based on a fluoride shuttle (fluoride ion battery, FIB) can theoretically provide high energy densities and can thus be considered as an interesting alternative to Li-ion batteries. Large improvements are still needed regarding their actual performance, in particular for the ionic conductivity of the solid electrolyte. At the current state of the art, two types of fluoride families can be considered for electrolyte applications: alkaline-earth fluorides having a fluorite-type structure and rare-earth fluorides having a tysonite-type structure. As regard to the latter, high ionic conductivities have been reported for doped LaF3 single crystals. However, polycrystalline materials would be easier to implement in a FIB due to practical reasons in the cell manufacturing. Hence, we have analyzed in detail the ionic conductivity of La(1-y)Ba(y)F(3-y) (0 ≤ y ≤ 0.15) solid solutions prepared by ball milling. The combination of DC and AC conductivity analyses provides a better understanding of the conduction mechanism in tysonite-type fluorides with a blocking effect of the grain boundaries. Heat treatment of the electrolyte material was performed and leads to an improvement of the ionic conductivity. This confirms the detrimental effect of grain boundaries and opens new route for the development of solid electrolytes for FIB with high ionic conductivities.

Dielectric Properties of Iron- and Sodium-Fumarate

NASA Astrophysics Data System (ADS)

Skuban, Sonja J.; Džomić, Tanja; Kapor, Agneš

2007-04-01

The behaviour of dielectric parameters such as relative dielectric constant (ɛ'), relative loss factor (V'') and ac conductivity of well known pharmaceutical materials Fe(II)-fumarate and sodium-fumarate have been studied as a function of temperature (range 303 K to 483 K) and frequency (range 0.1 Hz to 100 kHz).

A feasibility study of wearable activity monitors for pre-adolescent school-aged children

USDA-ARS?s Scientific Manuscript database

Understanding physical activity is key in the fight against childhood obesity. The objective of this study was to examine the feasibility of using certain wearable devices to measure physical activity among children. A qualitative study was conducted with 25 children aged 7 to 10 years to assess ac...

Characterization of an EPG waveform library for redbanded stink bug, Piezodorus guildinii (Westwood) (Hemiptera: Pentatomidae), on soybean plants

USDA-ARS?s Scientific Manuscript database

Studies were conducted with the redbanded stink bug, Piezodorus guildinii (Westwood), using AC-DC electropenetrography (EPG) to record feeding behaviors on vegetative (stem and leaflet) and reproductive (pod) tissues of soybean, Glycine max (L.). P. guildinii is a major pest of soybean in the Americ...

Global Survey of Anthropogenic Neighborhood Threats to Conservation of Grass-Shrub and Forest Vegetation

EPA Science Inventory

We report a survey of land cover patterns focusing on forest, grassland, and shrubland for the United States. To provide information for a national resource assessment, an integrated survey of patterns was conducted using a circa 2001 land cover map. The survey was designed to ac...

76 FR 60707 - Supplemental Standards for Ethical Conduct for Employees of the Department of the Treasury

Federal Register 2010, 2011, 2012, 2013, 2014

2011-09-30

... DEPARTMENT OF THE TREASURY Office of Financial Research 12 CFR Chapter XVI RIN 1505-AC38... Financial Research, Treasury. ACTION: Interim rule. SUMMARY: The Department of the Treasury (Department... chapter in Title 12 of the Code of Federal Regulations to incorporate certain post-employment prohibitions...

Accuracy of regeneration surveys in New England northern hardwoods

Treesearch

William B. Leak

2007-01-01

Four 5-ac demonstration harvests were initiated in 1951 on the Bartlett Experimental Forest, New Hampshire: light selection, moderate selection, diameter limit, and liquidation. In 1952 and 1959, regeneration surveys were conducted that measured several different attributes of the seedlings and saplings in the cutover stands. In 2005, the stands were remeasured to...

The Role of Organizational Learning Culture and Psychological Empowerment in Reducing Turnover Intention and Enhancing Citizenship Behavior

ERIC Educational Resources Information Center

Islam, Talat; Khan, Mubbsher Munawar; Bukhari, Fida Hussain

2016-01-01

Purpose: The purpose of this paper is to examine the association among organizational learning culture (OLC), psychological empowerment (PE), affective commitment (AC), organizational citizenship behavior and turnover intention. Design/Methodology/Approach: This study was undertaken via a questionnaire conducted among Malay-Chinese working in…

Characterization of Vertical Impact Device Acceleration Pulses Using Parametric Assessment: Phase II Accelerated Free-Fall

DTIC Science & Technology

2016-04-30

support contractor , Infoscitex, conducted a series of tests to identify the performance capabilities of the Vertical Impact Device (VID). The VID is a...C. Table 3. AFD Evaluation with Red IMPAC Programmer: Data Summary Showing Means and Standard Deviations Test Cell Drop Ht . (in) Mean Peak

Coarse woody debris in oak woodlands of California.

Treesearch

William D. Tietje; Karen L. Waddell; Justin K. Vreeland; Charles L. Bolsinger

2002-01-01

An extensive forest inventory was conducted to estimate the amount and distribution of coarse woody debris (CWD) on 5.6 million ac of woodlands in California that are outside of national forests and reserved areas. Woodlands consist primarily of oak (Quercus spp.) types and are defined as forestland incapable of producing commercial quantities of...

Laser-guided energetic discharges over large air gaps by electric-field enhanced plasma filaments

NASA Astrophysics Data System (ADS)

Théberge, Francis; Daigle, Jean-François; Kieffer, Jean-Claude; Vidal, François; Châteauneuf, Marc

2017-01-01

Recent works on plasma channels produced during the propagation of ultrashort and intense laser pulses in air demonstrated the guiding of electric discharges along the laser path. However, the short plasma lifetime limits the length of the laser-guided discharge. In this paper, the conductivity and lifetime of long plasma channels produced by ultrashort laser pulses is enhanced efficiently over many orders of magnitude by the electric field of a hybrid AC-DC high-voltage source. The AC electric pulse from a Tesla coil allowed to stimulate and maintain the highly conductive channel during few milliseconds in order to guide a subsequent 500 times more energetic discharge from a 30-kV DC source. This DC discharge was laser-guided over an air gap length of two metres, which is more than two orders of magnitude longer than the expected natural discharge length. Long plasma channel induced by laser pulses and stimulated by an external high-voltage source opens the way for wireless and efficient transportation of energetic current pulses over long air gaps and potentially for guiding lightning.

Signature of magnetoelectric coupling of xNiFe2O4 - (1-x)HoMnO3 (x = 0.1 and 0.3) multiferroic nanocomposites

NASA Astrophysics Data System (ADS)

Mandal, S. K.; Debnath, Rajesh; Singh, Swati; Nath, A.; Dey, P.; Nath, T. K.

2017-12-01

The magnetoelectric coupling of xNiFe2O4-(1-x)HoMnO3 (x = 0.1 and 0.3) multiferroics nanocomposites prepared through low temperature chemical pyrophoric reaction process has been investigated at room temperature. The signature of magnetoelectric coefficient of these nanocomposites is mainly due to the magnetostriction and magnetodielectric properties of the materials. These nanocomposites show the ferroelectric behaviour at room temperature. AC electrical properties of nanocomposites have been studied with applied magnetic fields and temperatures. Nyquist plots at different magnetic fields and temperatures have been fitted using parallel combinations of resistance-capacitor circuits. Moreover, we have estimated activation energy of those composites using Arrhenius relation, which indicates that same kinds of charge carrier are responsible for relaxation process in grain boundaries and grain of the sample. Furthermore, from the analysis of ac conductivity data as a function of frequency is attributed to the large polaronic hopping in the conduction process in the system.

Effect of Mn2+ doping on structural, electrical transport and dielectric properties of CoFe2O4 nanoparticles

NASA Astrophysics Data System (ADS)

Ansari, Mohd Mohsin Nizam; Khan, Shakeel; Bhargava, Richa; Ahmad, Naseem

2018-05-01

Manganese substituted cobalt ferrites, Co1-xMnxFe2O4 (0.0, 0.1, 0.2, 0.3 and 0.4) were successfully synthesized by sol-gel method. XRD analysis confirmed the formation of a single-phase cubic spinel structures having Fd-3m space group and crystallite size is found to be in the range of 12.9 - 15.5 nm. The lattice parameter increased from 8.4109 Å to 8.4531 Å with increasing Mn2+ ion doping. Dielectric constant (ɛ'), dielectric loss (tanδ) and ac conductivity (σac) were analyzed at room temperature as a function of frequency (42 Hz to 5 MHz) and the behavior is explained on the basis of Maxwell-Wagner interfacial polarization. DC electrical resistivity measurements were carried out by two-probe method. DC electrical resistivity decreases with increase in temperature confirms the semiconducting nature of the samples. Impedance spectroscopy method has been used to understand the conduction mechanism and the effect of grains and grain boundary on the electrical properties of the materials.

Ba doped Fe3O4 nanocrystals: Magnetic field and temperature tuning dielectric and electrical transport

NASA Astrophysics Data System (ADS)

Dutta, Papia; Mandal, S. K.; Nath, A.

2018-05-01

Nanocrystalline BaFe2O4 has been prepared through low temperature pyrophoric reaction method. The structural, dielectric and electrical transport properties of BaFe2O4 are investigated in detail. AC electrical properties have been studied over the wide range of frequencies with applied dc magnetic fields and temperatures. The value of impedance is found to increase with increase in magnetic field attributing the magnetostriction property of the sample. The observed value of magneto-impedance and magnetodielectric is found to ∼32% and ∼33% at room temperature. Nyquist plots have been fitted using resistance-capacitor circuits at different magnetic fields and temperatures showing the dominant role of grain and grain boundaries of the sample. Metal-semiconductor transition ∼403 K has been discussed in terms of delocalized and localized charge carrier.We have estimated activation energy using Arrhenius relation indicating temperature dependent electrical relaxation process in the system. Ac conductivity follow a Jonscher’s single power law indicating the large and small polaronic hopping conduction mechanism in the system.

Electronic measurement apparatus movable in a cased borehole and compensating for casing resistance differences

DOEpatents

Vail, W.B. III.

1991-12-24

Methods of operation are described for an apparatus having at least two pairs of voltage measurement electrodes vertically disposed in a cased well to measure the resistivity of adjacent geological formations from inside the cased well. During stationary measurements with the apparatus at a fixed vertical depth within the cased well, the invention herein discloses methods of operation which include a measurement step and subsequent first and second compensation steps respectively resulting in improved accuracy of measurement. The invention also discloses multiple frequency methods of operation resulting in improved accuracy of measurement while the apparatus is simultaneously moved vertically in the cased well. The multiple frequency methods of operation disclose a first A.C. current having a first frequency that is conducted from the casing into formation and a second A.C. current having a second frequency that is conducted along the casing. The multiple frequency methods of operation simultaneously provide the measurement step and two compensation steps necessary to acquire accurate results while the apparatus is moved vertically in the cased well. 6 figures.

Electronic measurement apparatus movable in a cased borehole and compensating for casing resistance differences

DOEpatents

Vail, III, William B.

1991-01-01

Methods of operation of an apparatus having at least two pairs of voltage measurement electrodes vertically disposed in a cased well to measure the resistivity of adjacent geological formations from inside the cased well. During stationary measurements with the apparatus at a fixed vertical depth within the cased well, the invention herein discloses methods of operation which include a measurement step and subsequent first and second compensation steps respectively resulting in improved accuracy of measurement. The invention also discloses multiple frequency methods of operation resulting in improved accuracy of measurement while the apparatus is simultaneously moved vertically in the cased well. The multiple frequency methods of operation disclose a first A.C. current having a first frequency that is conducted from the casing into formation and a second A.C. current having a second frequency that is conducted along the casing. The multiple frequency methods of operation simultaneously provide the measurement step and two compensation steps necessary to acquire accurate results while the apparatus is moved vertically in the cased well.

Laser-guided energetic discharges over large air gaps by electric-field enhanced plasma filaments

PubMed Central

Théberge, Francis; Daigle, Jean-François; Kieffer, Jean-Claude; Vidal, François; Châteauneuf , Marc

2017-01-01

Recent works on plasma channels produced during the propagation of ultrashort and intense laser pulses in air demonstrated the guiding of electric discharges along the laser path. However, the short plasma lifetime limits the length of the laser-guided discharge. In this paper, the conductivity and lifetime of long plasma channels produced by ultrashort laser pulses is enhanced efficiently over many orders of magnitude by the electric field of a hybrid AC-DC high-voltage source. The AC electric pulse from a Tesla coil allowed to stimulate and maintain the highly conductive channel during few milliseconds in order to guide a subsequent 500 times more energetic discharge from a 30-kV DC source. This DC discharge was laser-guided over an air gap length of two metres, which is more than two orders of magnitude longer than the expected natural discharge length. Long plasma channel induced by laser pulses and stimulated by an external high-voltage source opens the way for wireless and efficient transportation of energetic current pulses over long air gaps and potentially for guiding lightning. PMID:28053312

Temperature dependent charge transport studies across thermodynamic glass transition in P3HT:PCBM bulk heterojunction: insight from J-V and impedance spectroscopy

NASA Astrophysics Data System (ADS)

Sarkar, Atri; Rahaman, Abdulla Bin; Banerjee, Debamalya

2018-03-01

Temperature dependent charge transport properties of P3HT:PCBM bulk heterojunction are analysed by dc and ac measurements under dark conditions across a wide temperature range of 110-473 K, which includes the thermodynamic glass transition temperature (Tg ˜320 K) of the system. A change from Ohmic conduction to space charge limited current conduction at higher (⩾1.2 V) applied bias voltages above  ⩾200 K is observed from J-V characteristics. From capacitance-voltage (C-V) measurement at room temperature, the occurrence of a peak near the built-in voltage is observed below the dielectric relaxation frequency, originating from the competition between drift and diffusion driven motions of charges. Carrier concentration (N) is calculated from C-V measurements taken at different temperatures. Room temperature mobility values at various applied bias voltages are in accordance with that obtained from transient charge extraction by linearly increasing voltage measurement. Sample impedance is measured over five decades of frequency across temperature range by using lock-in detection. This data is used to extract temperature dependence of carrier mobility (μ), and dc conductivity (σ_dc ) which is low frequency extrapolation of ac conductivity. An activation energy of  ˜126 meV for the carrier hopping process at the metal-semiconductor interface is estimated from temperature dependence of σ_dc . Above T g, μ levels off to a constant value, whereas σ_dc starts to decrease after a transition knee at T g that can be seen as a combined effect of changes in μ and N. All these observed changes across T g can be correlated to enhanced polymer motion above the glass transition.

Comparison of stapedotomy minus prosthesis, circumferential stapes mobilization, and small fenestra stapedotomy for stapes fixation.

PubMed

Acar, Gül Ozbilen; Kivekäs, Ilkka; Hanna, Bassem M; Huang, Lin; Gopen, Quinton; Poe, Dennis S

2014-04-01

To compare the outcomes of 3 surgical techniques for primary stapes fixation: stapedotomy minus prosthesis (STAMP), circumferential stapes mobilization (CSM), and small fenestra stapedotomy (SFS). Retrospective review of 277 primary cases operated for stapes fixation from 1997 to 2007. Tertiary academic center. Consecutive adult and pediatric cases operated for conductive hearing loss because of stapes fixation. STAMP was performed for otosclerosis limited to the anterior footplate, CSM was conducted for congenital stapes fixation, SFS was performed for more extensive otosclerosis or anatomic contraindications to STAMP/CSM. Pure-tone audiometry was performed preoperatively and postoperatively (3-6 wk) and the most recent long-term results (≥ 12 mo). Ninety-nine ears in 90 patients had audiologic follow-up data over 12 months. Sixty-seven ears (68%) underwent SFS, 16 (16%) STAMP, and 16 (16%) CSM. There was significant improvement in average air conduction (AC) thresholds and air-bone gap (ABG) for all techniques. Mean ABG for SFS closed from 29 to 7.1 dB (SD, 6.0), for STAMP from 29 to 3.8 dB (SD, 5.8 dB), and for CSM from 34 to 20 dB (SD, 8.2 dB). AC results were better in the STAMP than in the SFS group, especially in high frequencies. Bone conduction improvements were seen in all groups, highest in STAMP (4.3 dB) and CSM (3.8 dB) groups, but the differences between groups were not statistically significant. Satisfactory hearing results were achieved with all the techniques, and STAMP showed better hearing outcomes, especially in high frequencies. CSM is a good option for children and patients in whom it is desirable to avoid a footplate fenestration or prosthesis. CSM and STAMP had significantly higher rates of revision for refixation than SFS.

Effect of ac electric field on the dynamics of a vesicle under shear flow in the small deformation regime

NASA Astrophysics Data System (ADS)

Sinha, Kumari Priti; Thaokar, Rochish M.

2018-03-01

Vesicles or biological cells under simultaneous shear and electric field can be encountered in dielectrophoretic devices or designs used for continuous flow electrofusion or electroporation. In this work, the dynamics of a vesicle subjected to simultaneous shear and uniform alternating current (ac) electric field is investigated in the small deformation limit. The coupled equations for vesicle orientation and shape evolution are derived theoretically, and the resulting nonlinear equations are handled numerically to generate relevant phase diagrams that demonstrate the effect of electrical parameters on the different dynamical regimes such as tank treading (TT), vacillating breathing (VB) [called trembling (TR) in this work], and tumbling (TU). It is found that while the electric Mason number (Mn), which represents the relative strength of the electrical forces to the shear forces, promotes the TT regime, the response itself is found to be sensitive to the applied frequency as well as the conductivity ratio. While higher outer conductivity promotes orientation along the flow axis, orientation along the electric field is favored when the inner conductivity is higher. Similarly a switch of orientation from the direction of the electric field to the direction of flow is possible by a mere change of frequency when the outer conductivity is higher. Interestingly, in some cases, a coupling between electric field-induced deformation and shear can result in the system admitting an intermediate TU regime while attaining the TT regime at high Mn. The results could enable designing better dielectrophoretic devices wherein the residence time as well as the dynamical states of the vesicular suspension can be controlled as per the application.

Microwave absorption performance of Ni(OH)2 decorating biomass carbon composites from Jackfruit peel

NASA Astrophysics Data System (ADS)

Guan, Hongtao; Wang, Huiya; Zhang, Yanlin; Dong, Chengjun; Chen, Gang; Wang, Yude; Xie, Jianbin

2018-07-01

The composite material of Ni(OH)2/biomass carbon have been prepared by a facile "carbonization-activation" procedure from Jackfruit peel and a subsequent water-bathing precipitation process. The biomass carbon material after activation (AC) is constituted of small particles and achieves a large specific surface area of 1602 m2/g. After decoration of Ni(OH)2 nanosheets, the Ni(OH)2/AC composites were investigated the microwave absorption performances in 2-18 GHz. The maximum reflection loss of the Ni(OH)2/AC composites reached -23.6 dB at 15.48 GHz with a thickness of 6 mm. Moreover, the fundamental mechanism based on conductivity, the polarization and defects is discussed. The present investigation offers a new possibility for the biomass based fabrication of potential microwave absorbing materials.

Indirect and direct costs of acute coronary syndromes with comorbid atrial fibrillation, heart failure, or both

PubMed Central

Ghushchyan, Vahram; Nair, Kavita V; Page, Robert L

2015-01-01

Background The objective of this study was to determine the direct and indirect costs of acute coronary syndromes (ACS) alone and with common cardiovascular comorbidities. Methods A retrospective analysis was conducted using the Medical Expenditure Panel Survey from 1998 to 2009. Four mutually exclusive cohorts were evaluated: ACS only, ACS with atrial fibrillation (AF), ACS with heart failure (HF), and ACS with both conditions. Direct costs were calculated for all-cause and cardiovascular-related health care resource utilization. Indirect costs were determined from productivity losses from missed days of work. Regression analysis was developed for each outcome controlling for age, US census region, insurance coverage, sex, race, ethnicity, education attainment, family income, and comorbidity burden. A negative binomial regression model was used for health care utilization variables. A Tobit model was utilized for health care costs and productivity loss variables. Results Total health care costs were greatest for those with ACS and both AF and HF ($38,484±5,191) followed by ACS with HF ($32,871±2,853), ACS with AF ($25,192±2,253), and ACS only ($17,954±563). Compared with the ACS only cohort, the mean all-cause adjusted health care costs associated with ACS with AF, ACS with HF, and ACS with AF and HF were $5,073 (95% confidence interval [CI] 719–9,427), $11,297 (95% CI 5,610–16,985), and $15,761 (95% CI 4,784–26,738) higher, respectively. Average wage losses associated with ACS with and without AF and/or HF amounted to $5,266 (95% CI −7,765, −2,767), when compared with patients without these conditions. Conclusion ACS imposes a significant economic burden at both the individual and society level, particularly when with comorbid AF and HF. PMID:25565859

Thermal conductivity measurement of fluids using the 3ω method

NASA Astrophysics Data System (ADS)

Lee, Seung-Min

2009-02-01

We have developed a procedure to measure the thermal conductivity of dielectric liquids and gases using a steady state ac hot wire method in which a thin metal wire is used as a heater and thermometer. The temperature response of the heater wire was measured in a four-probe geometry using an electronic circuit developed for the conventional 3ω method. The measurements have been performed in the frequency range from 1 mHz to 1 kHz. We devised a method to transform the raw data into well-known linear logarithmic frequency dependence plot. After the transformation, an optimal frequency region of the thermal conductivity data was clearly determined as has been done with the data from thin metal film heater. The method was tested with air, water, ethanol, mono-, and tetraethylene glycol. Volumetric heat capacity of the fluids was also calculated with uncertainty and the capability as a probe for metal-liquid thermal boundary conductance was discussed.

Quantum Transport near the Charge Neutrality Point in Inverted Type-II InAs/GaSb Field-Effect Transistors

NASA Astrophysics Data System (ADS)

Pan, W.; Klem, J. F.; Kim, J. K.; Thalakulam, M.; Cich, M. J.; Lyo, S. K.

2013-03-01

We present here our recent quantum transport results around the charge neutrality point (CNP) in a type-II InAs/GaSb field-effect transistor. At zero magnetic field, a conductance minimum close to 4e2 / h develops at the CNP and it follows semi-logarithmic temperature dependence. In quantized magnetic (B) fields and at low temperatures, well developed integer quantum Hall states are observed in the electron as well as hole regimes. Electron transport shows noisy behavior around the CNP at extremely high B fields. When the diagonal conductivity σxx is plotted against the Hall conductivity σxy, a conductivity circle law is discovered, suggesting a chaotic quantum transport behavior. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

Stabilizing Superionic-Conducting Structures via Mixed-Anion Solid Solutions of Monocarba- closo -borate Salts

DOE PAGES

Tang, Wan Si; Yoshida, Koji; Soloninin, Alexei V.; ...

2016-09-01

Solid lithium and sodium closo-polyborate-based salts are capable of superionic conductivities surpassing even liquid electrolytes, but often only at above-ambient temperatures where their entropically driven disordered phases become stabilized. Here we show by X-ray diffraction, quasielastic neutron scattering, differential scanning calorimetry, NMR, and AC impedance measurements that by introducing 'geometric frustration' via the mixing of two different closo-polyborate anions, namely, 1-CB 9H 10- and CB 11H 12-, to form solid-solution anion-alloy salts of lithium or sodium, we can successfully suppress the formation of possible ordered phases in favor of disordered, fast-ion-conducting alloy phases over a broad temperature range from subambientmore » to high temperatures. Finally, this result exemplifies an important advancement for further improving on the remarkable conductive properties generally displayed by this class of materials and represents a practical strategy for creating tailored, ambient-temperature, solid, superionic conductors for a variety of upcoming all-solid-state energy devices of the future.« less

Effect of blending and nanoparticles on the ionic conductivity of solid polymer electrolyte systems

NASA Astrophysics Data System (ADS)

Manjunatha, H.; Damle, R.; Kumaraswamy, G. N.

2018-05-01

In the present work, a polymer electrolyte blend containing polymers Poly ethylene oxide (PEO) and Poly (vinylidene fluoride-hexafluoropropylene) (PVDF-HFP) was prepared. The polymer blend was complexed with potassium trifluoromethanesulfonate (KCF3SO3), and titanium oxide nanoparticles (TiO2) (10nm size) were dispersed in to the complex at different weight percentages. The conductivity due to ions in the blend is determined by Ac impedance measurements in the frequency range of 10Hz-1MHz. The nano composite polymer blend containing 5wt% of TiO2 shows a conductivity of 7.95×10-5Scm-1, which is almost 1.5 orders more than polymer electrolyte with PEO as a polymer. XRD studies show a decrease in the coherence length of XRD peaks on addition of nanoparticles, which is due to increase the amorphous phase in the systems. Temperature dependence conductivity studies of the systems shows that, activation energy decreases with increase in the percentage of nanoparticles in the blend.

Effect of impurity resonant states on optical and thermoelectric properties on the surface of a topological insulator.

PubMed

Zhong, Min; Li, Shuai; Duan, Hou-Jian; Hu, Liang-Bin; Yang, Mou; Wang, Rui-Qiang

2017-06-21

We investigate the thermoelectric effect on a topological insulator surface with particular interest in impurity-induced resonant states. To clarify the role of the resonant states, we calculate the dc and ac conductivities and the thermoelectric coefficients along the longitudinal direction within the full Born approximation. It is found that at low temperatures, the impurity resonant state with strong energy de-pendence can lead to a zero-energy peak in the dc conductivity, whose height is sensitively dependent on the strength of scattering potential, and even can reverse the sign of the thermopower, implying the switching from n- to p-type carriers. Also, we exhibit the thermoelectric signatures for the filling process of a magnetic band gap by the resonant state. We further study the impurity effect on the dynamic optical conductivity, and find that the resonant state also generates an optical conductivity peak at the absorption edge for the interband transition. These results provide new perspectives for understanding the doping effect on topological insulator materials.

Proteomics of the Autographa californica Nucleopolyhedrovirus Budded Virions ▿

PubMed Central

Wang, RanRan; Deng, Fei; Hou, Dianhai; Zhao, Yong; Guo, Lin; Wang, Hualin; Hu, Zhihong

2010-01-01

Baculoviruses produce two progeny phenotypes during their replication cycles. The occlusion-derived virus (ODV) is responsible for initiating primary infection in the larval midgut, and the budded virus (BV) phenotype is responsible for the secondary infection. The proteomics of several baculovirus ODVs have been revealed, but so far, no extensive analysis of BV-associated proteins has been conducted. In this study, the protein composition of the BV of Autographa californica nucleopolyhedrovirus (AcMNPV), the type species of baculoviruses, was analyzed by various mass spectrometry (MS) techniques, including liquid chromatography-triple quadrupole linear ion trap (LC-Qtrap), liquid chromatography-quadrupole time of flight (LC-Q-TOF), and matrix-assisted laser desorption ionization-time of flight (MALDI-TOF). SDS-PAGE and MALDI-TOF analyses showed that the three most abundant proteins of the AcMNPV BV were GP64, VP39, and P6.9. A total of 34 viral proteins associated with the AcMNPV BV were identified by the indicated methods. Thirteen of these proteins, PP31, AC58/59, AC66, IAP-2, AC73, AC74, AC114, AC124, chitinase, polyhedron envelope protein (PEP), AC132, ODV-E18, and ODV-E56, were identified for the first time to be BV-associated proteins. Western blot analyses showed that ODV-E18 and ODV-E25, which were previously thought to be ODV-specific proteins, were also present in the envelop fraction of BV. In addition, 11 cellular proteins were found to be associated with the AcMNPV BV by both LC-Qtrap and LC-Q-TOF analyses. Interestingly, seven of these proteins were also identified in other enveloped viruses, suggesting that many enveloped viruses may commonly utilize certain conserved cellular pathways. PMID:20444894

Dielectric, Piezoelectric and Variable Range Hopping Conductivity Studies of Bi0.5(Na, K)0.5TiO3 Ceramics

NASA Astrophysics Data System (ADS)

Pattipaka, Srinivas; James, A. R.; Dobbidi, Pamu

2018-04-01

We report a detailed study on the structural, microstructural, piezoelectric, dielectric and AC conductivity of Bi0.5(Na1-x K x )0.5TiO3 (BNKT; x = 0, 0.1, 0.2 and 0.3) ceramics fabricated by a conventional solid-state reaction method. XRD and Raman analysis revealed that Bi0.5(Na0.8K0.2)0.5TiO3 and Bi0.5(Na0.7K0.3)0.5TiO3 ceramics exhibit a mixture of rhombohedral and tetragonal structures. The segregation of K at the grain boundary was confirmed by transmission electron microscopy and is related to typical microstructural local compositional mapping analysis. Two transitions, at ˜ 330°C and 150°C, observed from the ɛ' versus T curve in pure BNT are associated with the ferroelectric tetragonal to paraelectric cubic phase (T C) and ferroelectric rhombohedral to ferroelectric tetragonal phase (T d), respectively. Further, the T C and T d shifted towards the lower temperature with a rise in K concentration. Frequency dispersion of T d and T C suggest that BNKT ceramics exhibit a weak relaxor behavior with diffuse phase transition, which is confirmed by Uchino-Nomura criteria and the Vogel-Fulcher law. The AC resistivity ρ ac(T) follows the Mott variable range hopping conduction mechanism. A significant enhancement of dielectric and piezoelectric properties were observed for x = 0.2 system: dielectric constant (ɛ' = 1273), dielectric loss (tanδ = 0.047) at 1 kHz, electromechanical coupling coefficients (k ij : k 33, k t ˜ 60%, k 31 ˜ 62% and k p ˜ 46%), elastic coupling coefficients ( S_{33}D = 6.40 × 10-13 m2/N and S_{33}E = 10.06 × 10-13 m2/N) and piezoelectric constants (d 33 = 64.23 pC/N and g 33 = 5.69 × 10-3 Vm/N).

Effects of laser fluence non-uniformity on ambient-temperature soot measurements using the auto-compensating laser-induced incandescence technique

NASA Astrophysics Data System (ADS)

Liu, Fengshan; Rogak, Steven; Snelling, David R.; Saffaripour, Meghdad; Thomson, Kevin A.; Smallwood, Gregory J.

2016-11-01

Multimode pulsed Nd:YAG lasers are commonly used in auto-compensating laser-induced incandescence (AC-LII) measurements of soot in flames and engine exhaust as well as black carbon in the atmosphere. Such lasers possess a certain degree of fluence non-uniformity across the laser beam even with the use of beam shaping optics. Recent research showed that the measured volume fraction of ambient-temperature soot using AC-LII increases significantly, by about a factor of 5-8, with increasing the laser fluence in the low-fluence regime from a very low fluence to a relatively high fluence of near sublimation. The causes of this so-called soot volume fraction anomaly are currently not understood. The effects of laser fluence non-uniformity on the measured soot volume fraction using AC-LII were investigated. Three sets of LII experiments were conducted in the exhaust of a MiniCAST soot generator under conditions of high elemental carbon using Nd:YAG lasers operated at 1064 nm. The laser beams were shaped and relay imaged to achieve a relatively uniform fluence distribution in the measurement volume. To further homogenize the laser fluence, one set of LII experiments was conducted by using a diffractive optical element. The measured soot volume fractions in all three sets of LII experiments increase strongly with increasing the laser fluence before a peak value is reached and then start to decrease at higher fluences. Numerical calculations were conducted using the experimental laser fluence histograms. Laser fluence non-uniformity is found partially responsible for the soot volume fraction anomaly, but is insufficient to explain the degree of soot volume fraction anomaly observed experimentally. Representing the laser fluence variations by a histogram derived from high-resolution images of the laser beam energy profile gives a more accurate definition of inhomogeneity than a simple averaged linear profile across the laser beam.

Dielectric, Piezoelectric and Variable Range Hopping Conductivity Studies of Bi0.5(Na, K)0.5TiO3 Ceramics

NASA Astrophysics Data System (ADS)

Pattipaka, Srinivas; James, A. R.; Dobbidi, Pamu

2018-07-01

We report a detailed study on the structural, microstructural, piezoelectric, dielectric and AC conductivity of Bi0.5(Na1- x K x )0.5TiO3 (BNKT; x = 0, 0.1, 0.2 and 0.3) ceramics fabricated by a conventional solid-state reaction method. XRD and Raman analysis revealed that Bi0.5(Na0.8K0.2)0.5TiO3 and Bi0.5(Na0.7K0.3)0.5TiO3 ceramics exhibit a mixture of rhombohedral and tetragonal structures. The segregation of K at the grain boundary was confirmed by transmission electron microscopy and is related to typical microstructural local compositional mapping analysis. Two transitions, at ˜ 330°C and 150°C, observed from the ɛ' versus T curve in pure BNT are associated with the ferroelectric tetragonal to paraelectric cubic phase ( T C) and ferroelectric rhombohedral to ferroelectric tetragonal phase ( T d), respectively. Further, the T C and T d shifted towards the lower temperature with a rise in K concentration. Frequency dispersion of T d and T C suggest that BNKT ceramics exhibit a weak relaxor behavior with diffuse phase transition, which is confirmed by Uchino-Nomura criteria and the Vogel-Fulcher law. The AC resistivity ρ ac( T) follows the Mott variable range hopping conduction mechanism. A significant enhancement of dielectric and piezoelectric properties were observed for x = 0.2 system: dielectric constant ( ɛ' = 1273), dielectric loss (tan δ = 0.047) at 1 kHz, electromechanical coupling coefficients ( k ij : k 33, k t ˜ 60%, k 31 ˜ 62% and k p ˜ 46%), elastic coupling coefficients ( S_{33}D = 6.40 × 10-13 m2/N and S_{33}E = 10.06 × 10-13 m2/N) and piezoelectric constants ( d 33 = 64.23 pC/N and g 33 = 5.69 × 10-3 Vm/N).

2008 Spawning Cisco Investigations in the Canadian Waters of Lake Superior

USGS Publications Warehouse

Yule, Daniel; Addison, Peter A.; Evrard, Lori M.; Cullis, Ken I.; Cholwek, Gary A.

2009-01-01

The Great Lakes Science Center of the United States Geological Survey (USGS) is working cooperatively with the Ontario Ministry of Natural Resources (OMNR) on a threeyear study to develop standard procedures for acoustic and midwater trawl (AC-MT) assessments of spawning cisco Coregonus artedi that the OMNR can carry forward as a management activity. In year two (2008), we conducted an AC-MT survey of the northern shore from Nipigon Bay to Thunder Bay. Spawning-cisco (> 250 mm total length) densities were lowest near Nipigon Bay (<10/ha), moderate in and around Black Bay (15- 30/ha), and highest in Thunder Bay (118/ha). Rainbow smelt Osmerus mordax densities were highest in Nipigon (2,179/ha) and Black (3,219/ha) bays, and lowest in Thunder Bay (961/ha). We combined our AC-MT survey results with commercial catch records to estimate exploitation fractions of female cisco in Thunder Bay during the 2008 fishery at 4% for ages 1-5, 8.7% for ages 6-12, and 4.4% for ages ≥ 13. Lake Superior fishery managers recently recommended that annual exploitation of adult female lake cisco be kept below 10-15%. Recruitment of cisco since 2003 has been low and there is a strong probability the Thunder Bay stock will decline into the future. Using a simple population dynamics approach we estimated that if the current total allowable catch (TAC) quota is held constant, exploitation fractions could exceed 10% by 2010 and 15% by 2011. Our 2008 collections suggested the survey of Black Bay was likely conducted before all spawners had returned there to spawn. Our data also suggested that cisco collected in Black Bay and east of this site in mid-November may be from the same stock. During November 2009 we will attempt to get better definition of the area occupied by cisco around Black Bay and also determine when surveys should be conducted at this location.

Growth and characterization of diammonium copper disulphate hexahydrate single crystal

DOE Office of Scientific and Technical Information (OSTI.GOV)

Siva Sankari, R.; Perumal, Rajesh Narayana, E-mail: r.shankarisai@gmail.com

2014-03-01

Graphical abstract: Diammonium copper disulphate hexahydrate (DACS) is one of the most promising inorganic dielectric crystals with exceptional mechanical properties. Good quality crystals of DACS were grown by using solution method in a period of 30 days. The grown crystals were subjected to single crystal X-ray diffraction analysis in order to establish their crystalline nature. Thermo gravimetric, differential thermal analysis, FTIR, and UV–vis–NIR analysis were performed for the crystal. Several solid state physical parameters have been determined for the grown crystals. The dielectric constant and the dielectric loss and AC conductivity of the grown crystal were studied as a functionmore » of frequency and temperature has been calculated and plotted. - Highlights: • Diammonium copper disulphate is grown for the first time and CCDC number obtained. • Thermal analysis is done to see the stability range of the crystals. • Band gap and UV cut off wavelength of the crystal are determined to be 2.4 eV and 472.86 nm, respectively. • Dielectric constant, dielectric loss and AC conductivity are plotted as a function of applied field. - Abstract: Diammonium copper disulphate hexahydrate is one of the most promising inorganic crystals with exceptional dielectric properties. A good quality crystal was harvested in a 30-day period using solution growth method. The grown crystal was subjected to various characterization techniques like single crystal X-ray diffraction analysis, thermo gravimetric, differential thermal analysis, FTIR, and UV–vis–NIR analysis. Unit cell dimensions of the grown crystal have been identified from XRD studies. Functional groups of the title compounds have been identified from FTIR studies. Thermal stability of the samples was checked by TG/DTA studies. Band gap of the crystal was calculated. The dielectric constant and dielectric loss were studied as a function of frequency of the applied field. AC conductivity was plotted as a function of temperature.« less

A Technique for Estimating the Surface Conductivity of Single Molecules

NASA Astrophysics Data System (ADS)

Bau, Haim; Arsenault, Mark; Zhao, Hui; Purohit, Prashant; Goldman, Yale

2007-11-01

When an AC electric field at 2MHz was applied across a small gap between two metal electrodes elevated above a surface, rhodamine-phalloidin-labeled actin filaments were attracted to the gap and became suspended between the two electrodes. The variance of each filament's horizontal, lateral displacement was measured as a function of electric field intensity and position along the filament. The variance significantly decreased as the electric field intensity increased. Hypothesizing that the electric field induces electroosmotic flow around the filament that, in turn, induces drag on the filament, which appears as effective tension, we estimated the tension using a linear, Brownian dynamic model. Based on the tension, we estimated the filament's surface conductivity. Our experimental method provides a novel means for trapping and manipulating biological filaments and for probing the surface conductance and mechanical properties of single polymers.

Reduced conductivity and enhancement of Debye orientational polarization in lanthanum doped cobalt ferrite nanoparticles

NASA Astrophysics Data System (ADS)

Rahman, Atta ur; Rafiq, M. A.; Karim, S.; Maaz, K.; Siddique, M.; Hasan, M. M.

2011-12-01

In this work we have investigated the conductivity and dielectric properties of CoLaxFe2-xO4 (x=0.0, 0.03, 0.05, and 0.07) nanoparticles synthesized by chemical co-precipitation route. X-ray diffraction analysis confirms the inverse spinal structure of nanoparticles with slight increase in the lattice constant as La concentration increases. Transmission electron microscopy shows spherical nanoparticles with sizes of ∼20 nm. Impedance spectroscopy of the samples was performed in the frequency range 20 Hz-2 MHz at room temperature. The resistance of the grains and grain boundaries was found to increase with lanthanum concentration while the AC conductivity of the samples was observed to decrease with increasing La concentration. Dipolar orientational polarization was found to play an important role in determining dielectric properties of the samples.

Can Airports be a Green Source of Energy?

NASA Astrophysics Data System (ADS)

Solus, Daniel; Archer, Charysse; Malone, Brandi; Chesterfield, Norrisha; Jackson, Lateria; Erenso, Daniel

2008-04-01

When Boeing 747 lands its energy (896MJ) is dissipated by friction. Our statistical analysis for commercial aircrafts landing at the Nashville International Airport (BNA) have discovered that nearly 30 average single family households can be powered by the dissipated energy on a monthly basis. It may be possible to land an airplane on a frictionless surface and transform its energy into electrical energy. To demonstrate this we have conducted theoretical and experimental studies using a conducting rod attached to a toy car sliding on a U-shaped conducting wire placed in a uniform magnetic field track. The results concluded that this technique requires a very strong magnetic field. We then used a cylindrical magnet mounted on toy trucks and set to roll on a track inside a solenoid and been able to generate an ac voltage (4-10 volts).

Thermal conduction study of warm dense aluminum by proton differential heating

NASA Astrophysics Data System (ADS)

Ping, Y.; Kemp, G.; McKelvey, A.; Fernandez-Panella, A.; Shepherd, R.; Collins, G.; Sio, H.; King, J.; Freeman, R.; Hua, R.; McGuffey, C.; Kim, J.; Beg, F.

2016-10-01

A differential heating platform has been developed for thermal conduction study (Ping et al. PoP 2015), where a temperature gradient is induced and subsequent heat flow is probed by time-resolved diagnostics. An experiment using proton differential heating has been carried out at Titan laser for Au/Al targets. Two single-shot time-resolved diagnostics are employed, SOP (streaked optical pyrometry) for surface temperature and FDI (Fourier Domain Interferometry) for surface expansion. Hydrodynamic simulations show that after 15ps, absorption in underdense plasma needs to be taken into account to correctly interpret SOP data. Comparison between simulations with different thermal conductivity models and a set of data with varying target thickness will be presented. This work was performed under DOE contract DE-AC52-07NA27344 with support from OFES Early Career program and LLNL LDRD program.

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.

Malignant transformation of actinic cheilitis: A systematic review of observational studies.

PubMed

Dancyger, Alex; Heard, Victoria; Huang, Baikai; Suley, Cameron; Tang, Dorothy; Ariyawardana, Anura

2018-06-04

The aim of the present systematic review was to determine the malignant transformation rate of actinic cheilitis (AC). A comprehensive literature search was conducted using Medline/PubMed, Cumulative Index of Nursing and Allied Health Literature, Scopus, OvidSP, and Google Scholar. The inclusion criteria comprised of observational human studies involving the malignant transformation of AC and publications in English. Studies included in this review were clinical follow-up, cohort, retrospective, or prospective investigations. The search yielded 1126 articles, and after exclusion, 34 full-text articles were eligible for full-text analysis. Only one article met the inclusion criteria. Based on the included article, it was determined that the malignant transformation rate of AC to squamous cell carcinoma (SCC) was 3.07%. Excluded articles focused on the clinicopathological characteristics and treatment efficacies of AC, and no malignant transformation rate was assessed. There is a need for more clinical studies on the malignant transformation of AC, as lip cancer is a public health concern. High-risk populations, including those living in tropical regions, have excessive exposure to UV radiation, and have older aged males, fair-skinned people, and smokers should be identified to prevent AC and its malignant change. Health practitioners should facilitate early intervention to prevent the progression of AC to SCC of the lip. © 2018 John Wiley & Sons Australia, Ltd.

Electronic Circuit Analysis Language (ECAL)

NASA Astrophysics Data System (ADS)

Chenghang, C.

1983-03-01

The computer aided design technique is an important development in computer applications and it is an important component of computer science. The special language for electronic circuit analysis is the foundation of computer aided design or computer aided circuit analysis (abbreviated as CACD and CACA) of simulated circuits. Electronic circuit analysis language (ECAL) is a comparatively simple and easy to use circuit analysis special language which uses the FORTRAN language to carry out the explanatory executions. It is capable of conducting dc analysis, ac analysis, and transient analysis of a circuit. Futhermore, the results of the dc analysis can be used directly as the initial conditions for the ac and transient analyses.

Response of marine benthic fauna to thin-layer capping with activated carbon in a large-scale field experiment in the Grenland fjords, Norway.

PubMed

Samuelsson, Göran S; Raymond, Caroline; Agrenius, Stefan; Schaanning, Morten; Cornelissen, Gerard; Gunnarsson, Jonas S

2017-06-01

A field experiment with thin-layer capping was conducted in the Grenland fjords, Norway, for remediation in situ of mercury and dioxin-contaminated sediments. Experimental fields at 30 and 95 m depth were capped with (i) powdered activated carbon (AC) mixed with clay (AC+cla`y), (ii) clay, and (iii) crushed limestone. Ecological effects on the benthic community and species-feeding guilds were studied 1 and 14 months after capping, and a total of 158 species were included in the analyses. The results show that clay and limestone had only minor effects on the benthic community, while AC+clay caused severe perturbations. AC+clay reduced the abundance, biomass, and number of species by up to 90% at both 30 and 95 m depth, and few indications of recovery were found during the period of this investigation. The negative effects of AC+clay were observed on a wide range of species with different feeding strategies, although the suspension feeding brittle star Amphiura filiformis was particularly affected. Even though activated carbon is effective in reducing sediment-to-water fluxes of dioxins and other organic pollutants, this study shows that capping with powdered AC can lead to substantial disturbances to the benthic community.

Effect of fee-for-service air-conditioning management in balancing thermal comfort and energy usage.

PubMed

Chen, Chen-Peng; Hwang, Ruey-Lung; Shih, Wen-Mei

2014-11-01

Balancing thermal comfort with the requirement of energy conservation presents a challenge in hot and humid areas where air-conditioning (AC) is frequently used in cooling indoor air. A field survey was conducted in Taiwan to demonstrate the adaptive behaviors of occupants in relation to the use of fans and AC in a school building employing mixed-mode ventilation where AC use was managed under a fee-for-service mechanism. The patterns of using windows, fans, and AC as well as the perceptions of students toward the thermal environment were examined. The results of thermal perception evaluation in relation to the indoor thermal conditions were compared to the levels of thermal comfort predicted by the adaptive models described in the American Society of Heating, Refrigerating, and Air-Conditioning Engineers Standard 55 and EN 15251 and to that of a local model for evaluating thermal adaption in naturally ventilated buildings. A thermal comfort-driven adaptive behavior model was established to illustrate the probability of fans/AC use at specific temperature and compared to the temperature threshold approach to illustrate the potential energy saving the fee-for-service mechanism provided. The findings of this study may be applied as a reference for regulating the operation of AC in school buildings of subtropical regions.

A Comparison of Alternating Current and Direct Current Electrospray Ionization for Mass Spectrometry

PubMed Central

Sarver, Scott A.; Gartner, Carlos A.; Chetwani, Nishant; Go, David B.; Dovichi, Norman J.

2014-01-01

A series of studies comparing the performance of alternating current electrospray ionization (AC ESI) mass spectrometry (MS) and direct current electrospray ionization (DC ESI) MS has been conducted, exploring the absolute signal intensity and signal-to-background ratios produced by both methods using caffeine and a model peptide as targets. Because the high-voltage AC signal was more susceptible to generating gas discharges, the operating voltage range of AC ESI was significantly smaller than that for DC ESI, such that the absolute signal intensities produced by DC ESI at peak voltages were 1 - 2 orders of magnitude greater than those for AC ESI. Using an electronegative nebulizing gas, sulfur hexafluoride (SF6), instead of nitrogen (N2) increased the operating range of AC ESI by ~50%, but did not appreciably improve signal intensities. While DC ESI generated far greater signal intensities, both ionization methods produced comparable signal-to-background noise, with AC ESI spectra appearing qualitatively cleaner. A quantitative calibration analysis was performed for two analytes, caffeine and the peptide MRFA. AC ESI utilizing SF6 outperforms all other techniques for the detection of MRFA, producing chromatographic limits of detection nearly one order of magnitude lower than that of DC ESI utilizing N2, and one half that of DC ESI utilizing SF6. However, DC ESI outperforms AC ESI for the analysis of caffeine, indicating improvements in spectral quality may benefit certain compounds, or classes of compounds, on an individual basis. PMID:24464359

Diffusion tensor imaging of anterior commissural fibers in patients with schizophrenia.

PubMed

Choi, Hongyoon; Kubicki, Marek; Whitford, Thomas J; Alvarado, Jorge L; Terry, Douglas P; Niznikiewicz, Margaret; McCarley, Robert W; Kwon, Jun Soo; Shenton, Martha E

2011-08-01

Alterations in white matter connections in schizophrenia have been investigated using diffusion tensor imaging (DTI). There is also evidence from post-mortem studies as well as from magnetic resonance imaging morphometry studies that the anterior commissure (AC) might be implicated in schizophrenia, but no studies, to date, have investigated the AC using DTI or tractography. DTI scans were analyzed from 25 patients and 23 controls. Mean fractional anisotropy (FA) and trace were measured from the AC tracts. SANS and SAPS were used to evaluate clinical symptoms, and the Iowa Gambling Task, related to decision making, was also examined. Results revealed a significant decrease in mean FA and a significant increase in mean trace of AC tracts in patients compared with controls. In addition, patients, but not controls, showed a negative correlation between age and AC integrity. Statistically significant positive correlations were also found between AC FA and total positive symptom score. Decision making was negatively correlated with FA in patients on the Iowa Gambling Task, but not in controls. This study provides quantitative evidence for a reduction of interhemispheric connectivity in schizophrenia within the AC. Negative correlation between age and AC FA in the patients is consistent with the idea that schizophrenia may be a disorder of white matter maturation. Positive correlation between FA and positive symptom is discussed in the context of white matter's established role in modulating neural conduction velocity. Published by Elsevier B.V.

Dielectric and electrical study of PPy doped PVA-PVP films

NASA Astrophysics Data System (ADS)

Jha, Sushma; Tripathi, Deepti

2018-05-01

Dielectric parameters of free standing films of pure PVA (PolyvinylAlcohol) and PVA with varying concentrations of PVP(Polyvinylpyrrolidone) and Polypyrrole were prepared and studied in low frequency range (100Hz - 2MHz). The results show that dielectric constant, loss tangent and conductivity increase sharply on increasing the concentration of PVP above 50wt% in polymer matrix. PVA-PVP film with low concentration of PPy showed improvement in the values of complex permittivity, loss tangent and ac conductivity within the experimental frequency range. This eco - friendly polymeric material will be studied for its probable application for RFI/EMI shielding, biosensors, capacitors & insulation purposes.

Method to detect the end-point for PCR DNA amplification using an ionically labeled probe and measuring impedance change

DOEpatents

Miles, Robin R [Danville, CA; Belgrader, Phillip [Severna Park, MD; Fuller, Christopher D [Oakland, CA

2007-01-02

Impedance measurements are used to detect the end-point for PCR DNA amplification. A pair of spaced electrodes are located on a surface of a microfluidic channel and an AC or DC voltage is applied across the electrodes to produce an electric field. An ionically labeled probe will attach to a complementary DNA segment, and a polymerase enzyme will release the ionic label. This causes the conductivity of the solution in the area of the electrode to change. This change in conductivity is measured as a change in the impedance been the two electrodes.

Ambient temperature and emergency room admissions for acute coronary syndrome in Taiwan

NASA Astrophysics Data System (ADS)

Liang, Wen-Miin; Liu, Wen-Pin; Chou, Sze-Yuan; Kuo, Hsien-Wen

2008-01-01

Acute coronary syndrome (ACS) is an important public health problem around the world. Since there is a considerable seasonal fluctuation in the incidence of ACS, climatic temperature may have an impact on the onset of this disease. The objective of this study was to assess the relationship between the average daily temperature, diurnal temperature range and emergency room (ER) admissions for ACS in an ER in Taichung City, Taiwan. A longitudinal study was conducted which assessed the correlation of the average daily temperature and the diurnal temperature range to ACS admissions to the ER of the city’s largest hospital. Daily ER admissions for ACS and ambient temperature were collected from 1 January 2000 to 31 March 2003. The Poisson regression model was used in the analysis after adjusting for the effects of holiday, season, and air pollutant concentrations. The results showed that there was a negative significant association between the average daily temperature and ER admissions for ACS. ACS admissions to the ER increased 30% to 70% when the average daily temperature was lower than 26.2°C. A positive association between the diurnal temperature range and ACS admissions was also noted. ACS admissions increased 15% when the diurnal temperature range was over 8.3°C. The data indicate that patients suffering from cardiovascular disease must be made aware of the increased risk posed by lower temperatures and larger changes in temperature. Hospitals and ERs should take into account the increased demand of specific facilities during colder weather and wider temperature variations.

Enhanced biochars can match activated carbon performance in sediments with high native bioavailability and low final porewater PCB concentrations.

PubMed

Gomez-Eyles, Jose L; Ghosh, Upal

2018-07-01

A bench scale study was conducted to evaluate the effectiveness of in situ amendments to reduce the bioavailability of pollutants in sediments from a site impacted with polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs) and cadmium. The amendments tested included fine and coarse coal-based activated carbons (AC), an enhanced pinewood derived biochar (EPB), organoclay, and coke dosed at 5% of sediment dry weight. Strong reductions in total PCB porewater concentrations were observed in sediments amended with the fine AC (94.9-99.5%) and EPB (99.6-99.8%). More modest reductions were observed for the coarse AC, organoclay, and coke. Strong reductions in porewater PCB concentrations were reflected in reductions in total PCB bioaccumulation in fresh water oligochaetes for both the fine AC (91.9-96.0%) and EPB (96.1-96.3%). Total PAH porewater concentrations were also greatly reduced by the fine AC (>96.1%) and EPB (>97.8%) treatments. EPB matched or slightly outperformed the fine AC throughout the study, despite sorption data indicating a much stronger affinity of PCBs for the fine AC. Modeling EPB and fine AC effectiveness on other sediments confirmed the high effectiveness of the EPB was due to the very low final porewater concentrations and differences in the native bioavailability between sediments. However, low bulk density and poor settling characteristics make biochars difficult to apply in an aquatic setting. Neither the EPB nor the fine AC amendments were able to significantly reduce Cd bioavailability. Copyright © 2018 Elsevier Ltd. All rights reserved.

Measurement of volume resistivity/conductivity of metallic alloy in inhibited seawater by optical interferometry techniques

DOE Office of Scientific and Technical Information (OSTI.GOV)

Habib, K.

2011-03-15

Optical interferometry techniques were used for the first time to measure the volume resistivity/conductivity of carbon steel samples in seawater with different concentrations of a corrosion inhibitor. In this investigation, the real-time holographic interferometry was carried out to measure the thickness of anodic dissolved layer or the total thickness, U{sub total}, of formed oxide layer of carbon steel samples during the alternating current (ac) impedance of the samples in blank seawater and in 5-20 ppm TROS C-70 inhibited seawater, respectively. In addition, a mathematical model was derived in order to correlate between the ac impedance (resistance) and the surface (orthogonal)more » displacement of the surface of the samples in solutions. In other words, a proportionality constant [resistivity ({rho}) or conductivity ({sigma})= 1/{rho}] between the determined ac impedance [by electrochemical impedance spectroscopy (EIS) technique] and the orthogonal displacement (by the optical interferometry techniques) was obtained. The value of the resistivity of the carbon steel sample in the blank seawater was found similar to the value of the resistivity of the carbon steel sample air, around 1 x 10{sup -5}{Omega} cm. On the contrary, the measured values of the resistivity of the carbon steel samples were 1.85 x 10{sup 7}, 3.35 x 10{sup 7}, and 1.7 x 10{sup 7}{Omega} cm in 5, 10, and 20 ppm TROS C-70 inhibited seawater solutions, respectively. Furthermore, the determined value range of {rho} of the formed oxide layers, from 1.7 x 10{sup 7} to 3.35 x 10{sup 7}{Omega} cm, is found in a reasonable agreement with the one found in literature for the Fe oxide-hydroxides, i.e., goethite ({alpha}-FeOOH) and for the lepidocrocite ({gamma}-FeOOH), 1 x 10{sup 9}{Omega} cm. The {rho} value of the Fe oxide-hydroxides, 1 x 10{sup 9}{Omega} cm, was found slightly higher than the {rho} value range of the formed oxide layer of the present study. This is because the former value was determined by a dc method rather than by an electromagnetic method, i.e., holographic interferometry with applications of EIS, i.e., ac method. As a result, erroneous measurements were recorded due to the introduction of heat to Fe oxide-hydroxides.« less

AC and DC electrical behavior of MWCNT/epoxy nanocomposite near percolation threshold: Equivalent circuits and percolation limits

NASA Astrophysics Data System (ADS)

Alizadeh Sahraei, Abolfazl; Ayati, Moosa; Baniassadi, Majid; Rodrigue, Denis; Baghani, Mostafa; Abdi, Yaser

2018-03-01

This study attempts to comprehensively investigate the effects of multi-walled carbon nanotubes (MWCNTs) on the AC and DC electrical conductivity of epoxy nanocomposites. The samples (0.2, 0.3, and 0.5 wt. % MWCNT) were produced using a combination of ultrason and shear mixing methods. DC measurements were performed by continuous measurement of the current-voltage response and the results were analyzed via a numerical percolation approach, while for the AC behavior, the frequency response was studied by analyzing phase difference and impedance in the 10 Hz to 0.2 MHz frequency range. The results showed that the dielectric parameters, including relative permittivity, impedance phase, and magnitude, present completely different behaviors for the frequency range and MWCNT weight fractions studied. To better understand the nanocomposites electrical behavior, equivalent electric circuits were also built for both DC and AC modes. The DC equivalent networks were developed based on the current-voltage curves, while the AC equivalent circuits were proposed by using an optimization problem according to the impedance magnitude and phase at different frequencies. The obtained equivalent electrical circuits were found to be highly useful tools to understand the physical mechanisms involved in MWCNT filled polymer nanocomposites.

Vinpocetine inhibits Streptococcus pneumoniae-induced upregulation of mucin MUC5AC expression via induction of MKP-1 phosphatase in the pathogenesis of otitis media.

PubMed

Lee, Ji-Yun; Komatsu, Kensei; Lee, Byung-Cheol; Miyata, Masanori; O'Neill Bohn, Ashley; Xu, Haidong; Yan, Chen; Li, Jian-Dong

2015-06-15

Mucin overproduction is a hallmark of otitis media (OM). Streptococcus pneumoniae is one of the most common bacterial pathogens causing OM. Mucin MUC5AC plays an important role in mucociliary clearance of bacterial pathogens. However, if uncontrolled, excessive mucus contributes significantly to conductive hearing loss. Currently, there is a lack of effective therapeutic agents that suppress mucus overproduction. In this study, we show that a currently existing antistroke drug, vinpocetine, a derivative of the alkaloid vincamine, inhibited S. pneumoniae-induced mucin MUC5AC upregulation in cultured middle ear epithelial cells and in the middle ear of mice. Moreover, vinpocetine inhibited MUC5AC upregulation by inhibiting the MAPK ERK pathway in an MKP-1-dependent manner. Importantly, ototopical administration of vinpocetine postinfection inhibited MUC5AC expression and middle ear inflammation induced by S. pneumoniae and reduced hearing loss and pneumococcal loads in a well-established mouse model of OM. Thus, these studies identified vinpocetine as a potential therapeutic agent for inhibiting mucus production in the pathogenesis of OM. Copyright © 2015 by The American Association of Immunologists, Inc.