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1Author    D. Siebert, R. Miller, S. Fiechter, P. Dulski, A. HartmannRequires cookie*
 Title    An EPR Investigation of Cr 3+ and Ni 2 + in Synthetic Pyrite Crystals  
 Abstract    In many synthetic pyrite single crystals of high quality and purity we could detect Cr 3 + and Ni 2 + by EPR at 78 K as unwanted impurities. The assignment was possible by means of the isotopes Cr 53 and Ni 61 , occurring in natural abundance. The paramagnetic centers exhibit unusual g-values. In case of Ni 2+ a ligand hyperfine interaction could be observed beside the normal hyperfine interaction with the Ni 61 nucleus. For some crystals the Cr 3+ signal intensity could be increased up to ten times by temperature increasement from 78 K to about 100 K. At 78 K the Cr 3+ intensity was quenched by IR irradiation. 
  Reference    Z. Naturforsch. 45a, 1267—1272 (1990); received August 4 1990 
  Published    1990 
  Keywords    Pyrite, EPR, Paramagnetic ions, Conductivity 
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 TEI-XML for    default:Reihe_A/45/ZNA-1990-45a-1267.pdf 
 Identifier    ZNA-1990-45a-1267 
 Volume    45 
2Author    Josef Metz, Georg Pawlowski, Michael HanackRequires cookie*
 Title    Lösliche Phthalocyaninatometalloxane, Dotierung und Leitfähigkeit Soluble Phthalocyaninatometaloxanes, Doping and Conductivity  
 Abstract    The polymeric //-oxo-(tetraalkylphthalocyaninato)-metal IVB derivatives la-d were synthesized by thermal condensation of the monomeric dihydroxo(tetraalkylphthalo-cyaninato)-metal IVB compounds 5 a-d. The high solubility of the metaloxanes la-d enables a homogeneous reaction with the dopant. The electrical conductivities of the undoped and doped compounds are reported. 
  Reference    Z. Naturforsch. 38b, 378—382 (1983); eingegangen am 9. November 1982 
  Published    1983 
  Keywords    Phthalocyanine, Doping, Conductivity, Polymer 
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 TEI-XML for    default:Reihe_B/38/ZNB-1983-38b-0378.pdf 
 Identifier    ZNB-1983-38b-0378 
 Volume    38 
3Author    O. Wegener3, R. K. Üchler3, A. W. AtterichbRequires cookie*
 Abstract    12STe nuclear spin relaxation (NSR) and electrical conductivity measurements were performed on ultrapure single-crystalline paratellurite (a -T e0 2) between about 50 K and the melting point (1007 K) at various oxygen partial pressures (1 b a r -10"4 bar). At elevated temperatures the NSR rate l / 7 \ and conductivity a are caused by the diffusive motion o f point defects. From the observed p02-dependence of 1/Ti and a a defect model is developed which is shown to be consistent with the experimental data. The m odel involves ionic oxygen interstitials (O"), doubly charged oxygen vacancies (Vo') and charge-com pensating electron holes (h'). The observed pressure dependence suggests that the N SR rate is induced by the m otion of \ q while the conductivity is due to the m obility o f h*. Evaluation o f the data leads to 3.3 eV for the incorporation enthalpy o f oxygen on interstitial sites and to 4.5 eV for the formation enthalpy of oxygen Frenkel pairs (O "-V q'). Further, the chemical diffusion coefficient Dc is found to be caused by the ambipolar diffusion o f OS' and h \ At 950 K we obtained from both the NSR and conductivity experiments D c = (1 ± 0.3) • 10" 5 cm 2/s. 
  Reference    Z. Naturforsch. 49a, 1151 (1994); received August 22 1994 
  Published    1994 
  Keywords    Oxides, Point defects, Diffusion, N M R, Conductivity 
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 TEI-XML for    default:Reihe_A/49/ZNA-1994-49a-1151.pdf 
 Identifier    ZNA-1994-49a-1151 
 Volume    49 
4Author    M. Schüler, J. Dahlem, D. SiebertRequires cookie*
 Title    E P R I  
 Abstract    n v e s tig a tio n o f S y n th e tic , D o p e d F e S 2 a n d R u S 2 S in g le C r y s ta ls . Synthetic FeS2 and RuS2 single crystals were prepared by the flux method using PbCl2, bismut, and tellurium as different solvents. FeS2 and some RuS2 samples were doped with elementary vanadium, other RuS2 crystals with manganese and nickel. The EPR spectra revealed Mn2+ in the low-spin state and Ni2+. The lineshape of the Mn sextet turned out to be asymmetrical. In some RuS2 samples we detected an isotropic structureless rather narrow signal with a linewidth down to 0.05 mT and attributed it to the conductivity. Its lineshape becomes symmetrical and Lorentzian by grinding the samples to a polycrystalline powder. The EPR parameters of appropriate spin-Hamiltonians were determined. The intensities of the allowed and forbidden lines depended very differently on the microwave power due to different degrees of saturation. 
  Reference    Z. Naturforsch. 50a, 1159—1164 (1995); received October 17 1995 
  Published    1995 
  Keywords    FeS2, RuS2, EPR, paramagnetic ions, conductivity 
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 TEI-XML for    default:Reihe_A/50/ZNA-1995-50a-1159.pdf 
 Identifier    ZNA-1995-50a-1159 
 Volume    50 
5Author    HeinzP. Fritz, Helmut Gebauer, Peter Friedrich, Peter Ecker, Reinhold Artes, Ulrich SchubertRequires cookie*
 Title    Elektrochemische Synthesen, XIV [1] Radikalkation-Salze des Naphthalins Electrochemical Syntheses, XIV [1]. Radical Cation Salts of Naphthalene  
 Abstract    By anodic oxidation of naphthalene in H2CCI2/O.O2 m Bu4NPF6 at —45 °C dark red-violet crystals of (CioHshPFö can be obtained by electrocrystallisation. They are stable at low temperatures, however, decompose on warming. In solution and in the poly-crystalline state these radical cation salts show only narrow e.p.r. signals without h.f.s. The specific conductivity of a polycrystalline pellet at room temperature was determined to be 0.12 ±0.046 Ohm -1 cm -1 . The structure determination of (CioHs^PFe yielded the tetragonal space group P42/n, Z = 2, a = b = 1156(2), c = 640(1) pm. Patterson synthesis and difference Fourier analyses showed the compound to have a columnar stacking of CioHg units the long molecular axes of which are twisted alternately by 90° around a screw axis in c-direction, and the molecular planes of which are 320 pm apart. The PFß -ions have four nearest CioHs neighbours lying in pairs in parallel planes 63 pm above and below that plane of PF6~ perpendicular to the c-axis and containing a PF4 group. This is the first established case for a columnar structure of a pure hydrocarbon radical cation. (CIOH8)2AsF6 is isomorphous. 
  Reference    Z. Naturforsch. 33b, 498—506 (1978); eingegangen am 21. Februar 1978 
  Published    1978 
  Keywords    Naphthalene Radical Cation, X-ray, Columnar Structure, Conductivity 
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 TEI-XML for    default:Reihe_B/33/ZNB-1978-33b-0498.pdf 
 Identifier    ZNB-1978-33b-0498 
 Volume    33 
6Author    HeinzP. Fritz, Michael WeisRequires cookie*
 Title    Zur Charakterisierung zweier polymerer Kohlenstoffselenide Characterization of Two Polymerie Carbon Selenides  
 Abstract    A structure is suggested for the (amorphous) polymeric carbon selenide, (C 2 Se 3)", — obtained by heating (CSe 2)" in vacuum — on the basis of spectroscopic and electrochemical data. 
  Reference    Z. Naturforsch. 42b, 669—673 (1987); eingegangen am 24. Februar 1987 
  Published    1987 
  Keywords    Polymerie Carbon Selenides, Conductivity, Spectroscopic Data 
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 TEI-XML for    default:Reihe_B/42/ZNB-1987-42b-0669.pdf 
 Identifier    ZNB-1987-42b-0669 
 Volume    42 
7Author    Eberhard Bothe, D. Ietrich Schulte-FrohlindeRequires cookie*
 Title    Release of K+ and H+ from Poly U in Aqueous Solution upon y and Electron Irradiation. Rate of Strand Break Formation in Poly U  
 Abstract    Conductivity changes were found which followed the reaction of radiolytically generated OH radicals with the potassium salt of polyuridylic acid (poly U) in aqueous solution. After 60Co-y-irradiation the observed increase of conductivity at pH = 6.8 was shown to consist of the liberation of K+ ions from the stock of K+ ions electrostatically bound to the polyanion. The initial G(K+) is 36 and hence 6 times higher than the G value of OH radicals in N20 saturated solutions. At a poly U concentration of 60 mg I-1 half of the ion release occurred at 12 J kg-1 and nearly all ions are released at 40 J kg-1. The liberation of K+ is explained to be a consequence of the formation of chain breaks leading to an increase of the degree of dissociation. The rate of the ion release was studied under pulse radiolysis conditions. Because of the high G-vlaue of counterion liberation and the use of conductivity as analytical quantity the method is very sensitive. With 6 mg I-1 poly U the rate could be measured even at a dose per pulse of 0.25 J kg-1. The kinetics of the ion release can be described in terms of two parallel first order reactions of comparable contribution with an average rate constant of 0.8 s-i at 20 °C, 60 mg l-1 poly U and pH = 6.8 with a small contribution of slower components. In more acidic solutions, besides K+ ions H+ are also liberated since at low pH values bound K+ is replaced by H+. The rate of the ion release was found to increase with increasing replacement of K+ by H+ (^?bs = 100 s-1 at pH = 3.4, 60 mg I-1 poly U and T = 18 °C). With potassium ion free poly­ uridylic acid the corresponding rate constant amounted to 220 s_1, nearly independent of pH. From the temperature dependence activation parameters for the ion release were derived (£ a = 57 kJ mol-1, A = 1.0 x 1010 s— 1 at pH = 6.8). Addition of p-benzoquinone at pH = 3.7 and dithiothreitol (DTT) at pH 6.8 were found to decrease the size of the conductivity changes and to increase the rate. The results show that p-benzoquinone and DTT react with poly U radicals and that these reactions prevent chain breaks and ion liberation. It is concluded that the rate determining step of the conductivity increase is the formation of strand breaks by a cleavage of poly U radicals and that this reaction is pH dependent. The pH dependence and the observed value for the activation energy was found to be in agreement with the behaviour of a model system for the earlier postulated C-4' mechanism for strand break formation of polynucleotides and DNA. 
  Reference    Z. Naturforsch. 37c, 1191—1204 (1982); received July 5 1982 
  Published    1982 
  Keywords    Polyuridylic Acid, Irradiation, Conductivity, Strand Break, Rate 
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 TEI-XML for    default:Reihe_C/37/ZNC-1982-37c-1191.pdf 
 Identifier    ZNC-1982-37c-1191 
 Volume    37 
8Author    Eberhard Bothe, Dietrich Schulte-FrohlindeRequires cookie*
 Title    Aqueous Solution  
 Abstract    The bimolecular decay of the hydroxymethylperoxyl radical in aqueous solution (k = 2.1 x 10 9 M _1 s _1) leads mainly (80%) to one molecule of hydrogen peroxid and to two molecules of formic acid. 2 HOCHsOO--> H202 + 2 HCOOH Deuterium kinetic isotope effects show that the decay occurs at room temperature via a short lived (t < 10 -4 s) tetroxid. 
  Reference    Z. Naturforsch. 33b, 786—788 (1978); received February 20 1978 
  Published    1978 
  Keywords    a-Hydroxymethylperoxyl Radical, Pulse Radiolysis, Conductivity, Oxydation of Methanol 
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 TEI-XML for    default:Reihe_B/33/ZNB-1978-33b-0786.pdf 
 Identifier    ZNB-1978-33b-0786 
 Volume    33 
9Author    Eberhard Bothe, Dietrich Schulte-FrohlindeRequires cookie*
 Title    Reaction of Dihydroxymethyl Radical with Molecular Oxygen in Aqueous Solution  
 Abstract    Dihydroxymethyl radical (1) was found to react with oxygen diffusion controlled (k = 4.5 x 10 9 M _1 s -1). The final products of the reaction are formic acid and 1/2 hydrogen peroxide. The precursor of H2O2 was shown to be O2' -which is formed with G(02" -) = 6.3 (a value which includes the 02"~ formed by H atoms and oxygen (G(H) = 0.55)). If it is assumed that dihydroxymethylperoxyl radicals are formed as intermediates the rate constant of 02'~ formation must be > 10 6 s -1 . A bimolecular reaction of two dihydroxy-methylperoxyl radicals forming tetroxides does not occur at the dose rates used. The rate constants for the establishment of the equilibrium CH2(0H)2 + H2O2 CHaOH(OOH) + HaO k-3 have been determined at pH 5.7 and 19 °C to be k3=1.9x 10~ 2 M^s -1 and k_3 = 1.5 X 10~ 6 M _1 s _1 in aqueous solution. 
  Reference    Z. Naturforsch. 35b, 1035—1039 (1980); eingegangen am 7. März 1980 
  Published    1980 
  Keywords    Dihydroxymethyl Radical, Oxydation with Oxygen, Conductivity, Aqueous Solution 
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 TEI-XML for    default:Reihe_B/35/ZNB-1980-35b-1035.pdf 
 Identifier    ZNB-1980-35b-1035 
 Volume    35 
10Author    HeinzP. Fritz, Peter DavidRequires cookie*
 Title    Alkali-Polyketenenolat, ein Polyacetylen-Derivat Alkali-Polyketene-Enolate, a Polyacetylene Derivative  
 Abstract    An alkali-polyketene-enolate was made from polyketene by using aqueous bases MOH (M = Li, Na, K, Rb, Cs). The structure is proposed on the basis of IR and 13 C NMR spectra, the paramagnetic properties were investigated by EPR spectroscopy. AC conductivity measurements show a maximum conductivity of 1CT 2 Sern -1 (at 115 °C), where marked ionic participation is expected. Doping of the polyacetylene backbone with iodine gives no increase of conductivity; CV measurements indicate the presence of triiodide anions. 
  Reference    Z. Naturforsch. 43b, 671—676 (1988); eingegangen am 8. November 1987 
  Published    1988 
  Keywords    Alkali-Polyketene-Enolate, Polyketene, 13 C NMR Spectra, EPR Spectra, Conductivity 
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 TEI-XML for    default:Reihe_B/43/ZNB-1988-43b-0671.pdf 
 Identifier    ZNB-1988-43b-0671 
 Volume    43 
11Author    C. Ballario, A. Bonincontro, C. Cametti, A. Rosi, L. SportelliRequires cookie*
 Title    Effect of Extracellular Alkali Metal Salts on the Electric Parameters of Human Erythrocytes in Normal and Pathological Conditions (Homozygous ^-Thalassemia)  
 Abstract    The conductivity of human erythrocyte cells dispersed in various uni-univalent electrolyte solutions (NaCl, KC1, LiCl, CsCl; 0.15 m) have been measured in the frequency range from 10 KHz to 100 MHz at five temperatures between 5 and 45 °C. The results were analyzed in the light of the theory of conductivity polarization of a suspension of ellipsoidal particles covered with two confocal shells. Differences in the electrical parameters of the membrane between normal and homozygous /?-thalassemic cells have been evidentiated. 
  Reference    Z. Naturforsch. 39c, 1163—1169 (1984); received April 24/September 10 1984 
  Published    1984 
  Keywords    Conductivity, Radiowave Frequencies, Electrolyte Solutions, Erythrocytes, Homozygous /?-Thalassemic Erythrocytes 
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 TEI-XML for    default:Reihe_C/39/ZNC-1984-39c-1163.pdf 
 Identifier    ZNC-1984-39c-1163 
 Volume    39 
12Author    Hsin-Yi Hsu, Chao-Cheng YangRequires cookie*
 Title    Conductivities of Room Temperature Molten Salts Containing AICI3, Measured by a Computerized Direct Current Method  
 Abstract    The conductivities of the binary room-temperature molten salt systems AlCl3-yV-«-butylpyridinium chloride (BPC), AlCl3-l-ethyl-3-methylimidazolium chloride (EMIC) and AlCl3-benzyltriethylammo-nium chloride (BTEAC) have been measured at different temperatures and compositions by a d.c. four-probes method. There is a maximum of the conductivity at 50 mol% A1C13 in the A1C13-BPC and A1C13-EMIC systems at 40 to 80 °C, their activation energies being relatively low (20.79 and 14.76 kJ/mol, respec­ tively). As to the A1C13-BTEAC system, there is an irregular change in the conductivity at 40-70 mol% A1C13 in the temperature range 50 to 80 °C. The conductivities of the three RTMS are in the order A1C13-EMIC > A1C13-BPC > A1C13-BTEAC, the reason being discussed. 
  Reference    Z. Naturforsch. 56a, 670—676 (2001); received July 23 2001 
  Published    2001 
  Keywords    Conductivity, Room-temperature Molten Salts, Activation Energy, Direct Current Method, Computerized Measurement System 
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 TEI-XML for    default:Reihe_A/56/ZNA-2001-56a-0670.pdf 
 Identifier    ZNA-2001-56a-0670 
 Volume    56