Berechnung des zeitabhängigen dielektrischen Faktors und der zeitabhängigen spezifischen Leitfähigkeit relaxationsbehafteter Dielektrika aus frequenzabhängigen Messungen

Zusammenfassung Es werden Näherungen mitgeteilt, mit deren Hilfe die spezifische zeitabhängige Leitfähigkeit von relaxationsbehafteten Dielektrika aus der Verlustkomponentet" () des komplexen dynamischen dielektrischen Faktors ^*() berechnet werden kann. Die Näherungen sind wesentlich genauer als die bekannte Hamon-Näherung. Gegenüber der exakten Fouriertransformation von haben sie den Vorteil, daß einen nur in einem beschränkten Frequenzbereich um den Wert =1/t bekannt sein muß und daß sie sehr viel einfacher zu handhaben sind. Es handelt sich bei dieser Näherung um Linearkombinationen von-Werten, die an den Stützstellen= 1/2l _t , 1/2^-1 t,...2⁺¹ t l = 2,3,4 zu nehmen sind. Fürl = 4 beträgt der höchstmögliche Fehler der Näherung 0,8% des Wertes von ₀ () mit =1/t. ₀ steht für die dielektrische Feldkonstante.Desgleichen werden Näherungen abgeleitet, die es ermöglichen, den zeitabhängigen dielektrischen Faktor(t) aus der Speicherkomponente() von ^* () auf einfache Weise sehr genau zu ermitteln. Auch diese Näherungen stellen Linearbeziehungen von() an den Stützstellen = 2 ^q/t , 2^q–1/t,...., 1/2 ^r t,... dar. Dabei treten die-Werte an den mit 1/2 ^r abfallenden Stützstellen als Differenzen [()=1/2 ^r+1 t)- ( = 1/2 ^r t)] in einer unendlichen Summe auf, die sehr schnell konvergiert und im allgemeinen fürr = 3 abgebrochen werden kann. Es werden Näherungen fürq = 1, 2,3 angegeben.

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Summary Approximative formulas are derived, which allow to calculate the transient currenti(t) from the loss component() of the dielectric permittivity ^*(). These formulas are of great numerical simplicity and above all they do not require the knowledge of over the whole frequency range as the exact Fourier transformation formula does. The relations given consist of linear combinations of () taken at=1/2 t, 1/2 ^l–1t ,..., 2 ^l+1t forl = 2,3 or 4. The error bounds of the equation withl = 4 are less than 0,8% relative to ₀ (), = 1/t. ₀ is the dielectric constant of the vacuum.In a similar way the time-dependent dielectric factor(t) can be calculated from the storage component () of ^* (). It has been shown that(t) can be represented by a sum of ( = 1/t) and difference terms [( = 1/2 ^j+1 t) –( = 1/2jt)],j =q,q + 1, .... In general these difference terms become negligibly small forj > 3. There are equations given forq = –1, –2 and –3.

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Mit 2 Tabellen     

Evaluation of energy distribution on a heterogeneous surface from heat of adsorption and its application to the ammonia/Na-Y zeolite system

The— function (energy level function) which represents surface heterogeneity was derived from theq— function (experimental heat function) in the case of reversible adsorption. The Langmuir equation was extended and applied to the procedure of calculations. An iterative calculation led to the most probable— function by setting theq— function and adsorption temperature. As an example for actual cases, the— function of Na-Y zeolite was calculated from theq— function obtained by the measurement of heats of adsorption of ammonia at 373 K. The— function thus derived seemed to be consistent with the positional distribution of sodium ions.     

Order and disorder in mixed metal linear chains: The homo and heterobimetallic EDTA (M(H2O)4OIOII)[M′(EDTA)] · 6H2O complexes (M = Mg,Mn, Co,Zn and Ni; M′ = Co,Ni, Cu and Zn)

Summary Polymetallic solid solutions of the ethylenediaminetetracetic acid (EDTA) and six divalent metal ions exist in the range: MgMnCoZnNiCu(EDTA) · 6H₂O where + + + + + =2, 01, 0,,2, 0, 1.This type of structure is characterized by the presence of two different octahedral carboxylate-bridged coordination sites forming infinite zig-zag chains. Visible and i.r. spectra and t.g.a. analysis show that there is occupational preference for the two coordination sites in the crystalline structure.Due to this preference, and also to the structural features, the heterobimetallic MM(EDTA) · 6H₂O compounds constitute a structurally new class of materials which can be described as ordered alternating-heterobimetallic polymeric coordination complexes.     

Empirical equations of state for adsorption layer: Alkylthiopolyoxyethylene glycols

Surface tension isotherms ofn-alkylthiopolyoxyerhylene glycols:n-C _x H_2x+1S(CH₂CH₂O) _y H, wherex=5 to 8,y=3 or 4, were approximated with orthogonal polynomials to get good quality values of surface pressure (II) and molar area of the adsorbed layer (). The modified Volmer (*(–₀)=Z*R*T) van der Waals and virial equations of state were used to correlate and in terms of real two-dimensional gas. The combination of Volmer and van der Waals equations of state made it possible to determine the interaction energy, , which was prescribed to cohesion of hydrophobic chains in the adsorption layer. The value of for the amphiphiles in question was in the range 0.97–1.91R*T and the average contribution per methylene group was ca. 0.21R*T.The Lennard-Jones potentials calculated from second virial coefficient were of the same range as , but no clear relation was found between their values and number of structure elements of the alkylthiopolyoxyethlene glycols.Presented during 7th International Conference: Surface and Colloid Science, July 7–13, 1991, Compiegne, France     

Circulardichroismus. XXX

Zusammenfassung Es wird eine einfache Anordnung beschrieben, die es gestattet, auf einem Zweitschreiber zum Roussel-Jouan-Dichrographen wahlweise direkt oder / aufzuzeichnen. Integration der letzteren Kurve mit einem Planimeter gibt (unter Berücksichtigung der entsprechenden Faktoren) dann die Rotationsstärke der betrachteten CD-Bande, auch wenn diese starke Peinstruktur zeigt.

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Circular dichroism XXX. On the direct determination of the rotatory strength by the roussel-jouan dichrograph

A simple device is described which can be used with the Roussel-Jouan Dichrograph to give direct readings of s and /, resp. Integration of the latter curve with a planimeter yields the rotatory strength of any partial CD-band.

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Der Deutschen Forschungsgemeinschaft danken wir sehr für die großzügige Unterstützung unserer Arbeiten.

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XXIX. Mitteilung: Snatzke, G., u. K. Schaffner [10].

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Herrn Prof. Dr. E. Asmus zum 60. Geburtstag gewidmet.     

Über Lactame und cyclische Peptide, 6. Mitt.: Verwendung von Perbromiden und N-Brom-Derivaten des ε-Caprolactams und Cyclooligamids der ε-Amino-capronsäure als Bromierungs- und Dehydrierungsmittel

Zusammenfassung Perbromide und N-Brom-Derivate des -Caprolactams sowie des Cyclodiamids und Cyclooligomerengemisches der -Aminocapronsäure erweisen sich als Bromierungs- und Dehydrierungsmittel. Die Vorteile dieser neuen Methode werden an Hand von Beispielen demonstriert.

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Lactams and cyclopeptides, VI.: Perbromides and N-bromo derivatives of -caprolactam, and of -aminocaproic acid Cyclooligoamides as brominating and dehydrogenating agents

Perbromides and N-bromo derivatives of -caprolactam, -aminocaproic acid cyclodiamide and its cyclooligomers have been found to be versatile brominating and dehydrogenating agents. Some examples of their application are given.

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Mit 2 Abbildungen

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5. Mitt.:J. Krösi undP. Berencsi, Chem. Ber.101, 1979 (1968); Magyar Kémiai Folyóirat74, 214 (1968); Chem. Abstr.69, 52 114 (1968).     

Numerisch einfache Bezichungen zwischen Verlust- und Speicherkomponente des dynamischen dielektrischen Faktors

Zusammenfassung Es werden Formeln hergeleitet, die wie die Kramers-Kronig-Beziehungen Verlust- und Speicherkomponente des dynamischen komplexen dielektrischen Faktors*() miteinander in Verbindung bringen, die aber den Vorteil haben, daß kein Integral mehr auftritt und daß sich der Einfluß der jeweiligen Kurvenausläufer für bzw. 0 in Form einer einfach gebauten Summe aus Stützstellenwerten darstellen läßt. Die Stützstellen steigen mit dem Faktor 2 an, bzw. fallen mit dem Faktor 1/2 ab.So lassen sich die Glieder mit experimentell nicht zugänglichen Meßwerten eliminieren und lineare Näherungsgleichungen zwischen wenigen Stützstellenwerten der einen und der anderen Komponente finden. Die Genauigkeit dieser Näherungen läßt sich relativ zur Verlustkomponente. angeben. Die Beziehungen sind sehr gut geeignet, Meßungenauigkeiten aufzuzeigen und durch Nachkorrektur auszugleichen.Außerdem werden zwei Beziehungen gefunden, mit deren Hilfe die logarithmische Ableitung der Speicherkomponente aus wenigen Stützstellenwerten von. und einfach berechnet werden kann. Diese negative logarithmische Ableitung von scheint noch besser geeignet als., Dispersionsstufen durch Maxima anzuzeigen. Schließlich wird eine Formel aufgestellt, mit der aus dynamischen Messungen eine obere Grenze für die statische Leitfähigkeit ausgerechnet werden kann.

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Summary Formulas are derived, which relate the loss component. to the storage component of the dielectric permittivity* as the Kramers-Kronig equations do. The advantage of the formulas given is, that they involve simple sums of functional values instead of integrals. The influence of unaccessible parts of either. or, when is too large or too small for measurements, can be estimated easier. By combining the equations at different values of it is possible to eliminate the functional values at very large and at very small values of. Thus relations are obtained, which are very useful for checking measurements as is shown by application for an example of experimental data.Additional relations are given, which allow to calculate the logarithmic derivative of from a few values of and. The negative logarithmic derivative of seems to indicate transitions of materials more clearly than does. Finally a formula is derived, which allows to calculate an upper limit of the static conductivity from dynamic measurements.

     

ϑ-TaN,eine Hochdruckform von Tantalnitrid

Zusammenfassung Die gewöhnliche hexagonale Form von Tantalnitrid, -TaN (B35-Typ), geht bei 20 bis 100 kbar und 800 bis 960 °C in eine Hochdruckform -TaN (WC-Typ) über. Diese Form zeigt nach Abkühlen und Druckentlastung bei Normalbedingungen eine Höhere Dichte und kleinere Ta–N-Abstände als die Niederdruckform -TaN.

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-TaN,A high pressure form of tantalum nitride

The common hexagonal form of tantalum nitride, -TaN (B35-type), is converted to a high pressure form -TaN (WC-type) using pressures of 20 to 100 kbar and temperatures of 800 to 960°C. The high-pressure form, after cooling and pressure relaxation, shows at normal conditions a higher density and shorter distances Ta–N than the low-pressure -TaN.

     

Dielectric properties of moist CaCO3 filled polyethylene composites

The capacitance and the dielectric loss tangents of CaCO₃ filled polyethylene composites were studied. Composite samples, prepared by polymerizing ethylene on the surfaces of fillers, pre-treated by polymerization catalysts, were compared to normal mechanical mixtures. Dielectric dispersion,, and loss, , proved to be sensitive to heating or vacuum treatment. Investigation of samples under conditions of different relative humidities showed that the dielectric dispersion is due to adsorbed water. Both and increased with decreasing frequency and the ratio of loss and dispersion was nearly constant. Dielectric data measured at different relative humidities could be represented by a single Cole-Cole plot. Samples soaked in water for different periods yielded qualitatively similar but quantitatively different Cole-Cole plots. Composite samples showed higher losses at similar humidities.Possible interpretations in terms of a molecular relaxation model, an interfacial relaxation model, including a charged double layer mechanism, percolation theory and the universal response theory were examined, but none was able to fully explain the observed phenomena.     

Validity of energy distribution derived from heat of adsorption in an ammonia/cation-exchanged Y zeolite system

The validity of- functions (energy level functions) which were derived from experimentalq- functions (heat functions) was examined in an ammonia/cation-exchanged Y zeolite system. The- functions of Na-Y zeolite and Cs-Na-Y zeolite were respectively calculated from theirq- functions measured by ammonia adsorption at 373 K. The heat of adsorption of ammonia was also measured on a mixture of these two zeolites at a certain mixing ratio at 373 K. The- function of the mixture was likewise calculated on the basis of this measurement. The- function thus calculated was in good agreement with the synthesized- function derived by linearly combining two- functions of each zeolite mentioned above. The- function derived from experimental- function thus proved to be valid in an actual adsorption system.     

The relation between the nonlinear dielectric effect and solvent polarity

The relation between solvent polarity expressed through the Dimroth-Reichardt spectroscopic parameter E _T (30) and the nonlinear dielectric effect (NDE) expressed through the parameter /E² is demonstrated where is a change in the electric permittivity of a solvent in an external strong electric field E. Both E _T (20) and /E², determined in quite different ways, are extremely sensitive to the dielectric properties of a solvent which depend on molecular interactions. Linear correlations between /E² and E _T (30) have been found for n-alkanols representing hydrogenbond donor solvents, and for halogenobenzenes which are dipolar, aprotic, weakly-associated solvents.Part of this work was presented at The 22^nd International Conference on Solution Chemistry in Linz, Austria, July 1991.     

Detection of <Emphasis Type="Italic">N</Emphasis>-monomethyl-lysine generated by metabolic transmethylation

Administration of radiolabelled deprenyl to rats resulted in the urinary elimination of a ¹⁴C-labelled N-monomethyl-lysine. An increased level of N-monomethyl-lysine was found following an oral dose of another drug, also containing an N-methyl group. The urine sample was treated with 9-fluorenylmethoxycarbonyl chloride and then subjected to high-performance liquid chromatography (HPLC); the radioactive fraction was identified as N-monomethyl-lysine by using HPLC-MS in electrospray mode. Identification of N-monomethyl-lysine in the radioactive fraction gives experimental proof of transmethylation from a well-known drug to an endogenous compound.     

Complex polarizability as used to analyze dielectric relaxation measurements

The effect of representing dielectric properties in terms of the complex polarizability ^c = – i is examined. Loss curves ( and tan ) are shifted towards higher frequencies, revealing the existence of new relaxations and allowing the clarifications of ones already known. We have calculated the shift ratios (at maximum or tan )/ (at maximum or tan ) from the more conventional empirical equations representing the dielectric behavior. Some examples are given.     

Effect of the Allyl Group in Reactions of Allyl Alcohol and Its Derivatives with ε-Caprolactam

Unlike saturated alcohols, allyl alcohol reacts with -caprolactam under considerably milder conditions. Allyl esters react with -caprolactam to give the corresponding allyl -acylaminocaproates. The yield of the latter decreases in going from formyl to acetyl and propionyl derivatives. The observed effect of the allyl group is explained in terms of possible allylic rearrangement in the transition state.     

Interaction of a Single State with a Known Infinite System Containing One-Parameter Eigenvalue Band

Interaction of a quantum system S ₁ ^a containing a single state |> with a known infinite-dimensional quantum system S ^b containing an eigenvalue band [ _a , _b ] is considered. A new approach for the treatment of the combined system S =S ₁ ^a S ^b is developed. This system contains embedded eigenstates |()> with continuous eigenvalues [ _a , _b ], and, in addition, it may contain isolated eigenstates | _I > with discrete eigenvalues _I [ _a , _b ]. Exact expressions for the solution of the combined system are derived. In particular, due to the interaction with the system S ^b , eigenvalue E of the state |> shifts and, in addition, if E[ _a , _b ] this shifted eigenvalue broadens. Exact expressions for the eigenvalue shift and for the eigenvalue distribution of the state |> are derived. In the case of the weak coupling this eigenvalue distribution reduces to the standard resonance curve. Also, exact expressions for the time evolution of the state |(t)> that is initially prepared in the state |(0)>|> are obtained. Here again in the case of the weak coupling this time evolution reduces to the familiar exponential decay. The suggested method is exact and it applies to each coupling of the system S ₁ ^a with the system S ^b , however strong. It also presents a relatively good approximation for the interaction of a nondegenerate eigenstate | _s > of an arbitrary system S ^a with an infinite system S ^b containing a single eigenvalue band, provided this eigenstate is relatively well separated from other eigenstates of S ^a and provided the interaction between the systems S ^a and S ^b is not excessively strong.     

Activity in CO oxidation of manganese dioxide for batteries

The low temperature oxidation of CO over MnO₂ containing samples for batteries has been investigated. It is found that the samples contain compositional and hydrate water and Mn⁴⁺, Mn³⁺, Mn²⁺ ions. The high efficiency is due to Mn⁴⁺ content.

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CO MnO₂, . , Mn⁴⁺, Mn³⁺, Mn²⁺. Mn⁴⁺.

     

On the Role of Surface Forces in Contact Interaction between Elastic Sphere and Hard Surface

The works preformed earlier were reviewed briefly, and the new problem of the contact interaction between the elastic sphere and hard surface was formulated. The solution of a problem to the generalized surface force and its contact and noncontact components was obtained. The specific case of the obtained solution, when the separation = 0, was considered. The existence of two states of contact interaction between the elastic sphere and hard plane was revealed at = 0: (i) the stable state, at contact with the neck of radius a ₁= , where Ris the sphere radius, = (1 – )/(E), Eis the modulus of elasticity of the sphere, is its Poisson's coefficient, and () is the specific energy of adhesion of the surfaces at the lowest possible separation between these surfaces; and (ii) the unstable (metastable) state, at contact with radius a ₂= 0, i.e., at the point contact between the sphere and the plane. In this case, however, the stable contact with the neck at 0 when the modulus of elasticity E , i.e., at the interaction between the hard sphere and hard plane, is also degenerated into the point contact. It was shown that at the point contact, the contact component F _s ^"of the generalized surface force F _svanishes, whereas the noncontact component F _s ^"acquires the value F _s ^"= F _s= 2R() equal to the force of adhesion.     

Simple statistical mechanics of electrolytes with a concentration dependent dielectric constant. Part 1. The pressure equation

We have used an approximation of the Adelman's theory of solutions to take into account the non-pairwise additive effects on the interaction potentials for a real electrolyte solution. As a result, a solute concentration dependent dielectric constant appears. The comparison with experimental data is done by means of the pressure equation. The influence of on solution properties is analyzed in two molality ranges using as a reference simplified models but with the dielectric constant of the pure solvent instead of .     

On theC v toC p conversion for solid linear macromolecules

TheC _v toC _p conversion for solid linear macromolecules via the Nernst-Lindemann equationC _p -C _v =A ₀,C _p ² T/T_m is discussed on hand of data for 10 crystals and seven glasses. An average value ofA ₀=(5.11±2.41) · 10^–3 mol K J^–1 was calculated if the mole is assumed to refer to heavy atoms only. ThisA ₀ is numerically equal to the original Nernst—Lindemann constant.

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Zusammenfassung An Hand von sich auf 10 Kristalle und 7 Gläser beziehenden Daten wird die Umrechnung vonC _v -inC _p -Werte für feste lineare Makromoleküle mittels der Nernst-Lindemann-GleichungC _p -C _v =A ₀ C _p ² T/T _m diskutiert. Ein Durchschnittswert vonA ₀=(5.11±2.41) · 10^–3 mol K J^–1 wurde unter der Annahme berechnet, daß sich das Mol nur auf schwere Atome bezieht. DieserA ₀-Wert ist numerisch gleich der ursprünglichen Nerns-Lindemann-Konstanten.

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10 , - C _v C _p , —C _p –C _v = _{0 p} ² / . , , ₀ (5.11±2.41) · 10^–3 · ^–1. ₀ — .

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Support by the National Science Foundation, Polymers Program (Grant No. DMR 83-17097) is gratefully acknowledged.     

Hydrogen bonding in ε-caprolactam dimer: a quantum-chemical study

The equilibrium geometries, vibrational frequencies, and IR band intensities were calculated for the monomer and hydrogen-bonded cyclic dimer of -caprolactam (1) by the density functional B3LYP/6-311++G(d,p) method and compared with the experimental data. The gas phase IR spectrum of monomer of 1 was first measured. The calculated hydrogen bonding enthalpy H/2 in the hydrogen-bonded dimer in the gas phase (–5.93 kcal/mol) is consistent with the published data. The computed scaled (scaling factor 0.97) vibrational frequencies of the monomer and dimer are in good agreement with the experimental data. The geometry of the -caprolactam monomer remains nearly unchanged in its dimer except for the N-H, C-O, and C-N bond lengths that respectively change from 1.012, 1.230, and 1.369 in the former to 1.029, 1.246, and 1.350 in the latter. The frequencies, eigenvectors, and IR intensities of the amide modes of the monomer and dimer differ dramatically. The calculated NH and CO frequency shifts due to hydrogen bonding are in good agreement with the experimental data, but theoretical intensification of the NH IR band is much greater than that observed experimentally (by nearly 69 times vs. 11 times, respectively). The calculated N...O intermolecular distance in the structure of -caprolactam dimer equals the experimental value (2.89 ). The influence of the basis set employed on the results of calculations is discussed.Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1818–1825, September, 2004.