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     

TPD of ammonia from H-ZSM-5 zeolites deactivated during coupled methanol hydrocarbon cracking (CMHC)

The deactivation of H-ZSM-5 zeolite samples during coupled methanol/hydrocarbon cracking (CMHC) with n-butane as feed has been investigated in two different reaction modes (with intermediate regeneration and without regeneration). TPDA was used to characterize strong Brönsted acidity of fresh, regenerated and steamed H-ZSM-5 zeolite. The prevention of dealumination by blocking the acid centers with carbonaceous products could be proved, but the conversion rate of n-butane and the olefin selectivity declined drastically with increasing coking rate. H-ZSM-5 - / - - ( -). , - H-ZSM-5. - , , - - .     

The synthesis of ω-thienylalkane acids from ω-chloroalkane acids

Summary We have worked out a preparative method for the synthesis of -thienylalkane acids by acylation of thiophene with -chloroalkane acid chlorides followed by conversion of the resulting -chloroalkyl(2-thienyl)ketones into the corresponding acids by reaction with sodium malonic ester or potassium cyanide, and reduction of the resulting products with their simultaneous hydrolysis.Here and later we mean -(2-thienyl)alkne acids.We take this opportunity to thank R. Kh. Freidlina, A. A. Beér, and M. A. Besprozvannii for giving us enough -chloroalkane acids.     

Some observations of HZSM-5 zeolite dehydroxylation

The dehydroxylation of 3610 cm^–1 OH groups in HZSM-5 zeolite and in two Ni and Mo modified catalysts containing the same zeolite has been studied at 673 K. The presence of water vapor is a necessary condition of dehydroxylation, the extent of which depends on the number and duration of breaks consisting in cooling to room temperature and reheating to 673 K with evacuation. OH HZSM-5, Ni Mo- , 3610 cm^–1, 673 . , 673 .     

Synthesis of modified amino acids containing nucleic acid purine bases

The reaction of hydrazides of adenylyl- or hypoxanthinyl-9-alkylcarboxylic acids with sodium nitrite in acid media gives reactive azides of purinyl-9-alkylcarboxylic acids which condense with ()-aminocarboxylic and ,-diaminocarboxylic acids to give N(N)-(adenylyl-9-alkanoyl) aminocarboxylic, N-(adenylyl-9-)- and N-(hypoxanthinyl-9-alkanoyl)-,-diaminocarboxylic acids. The deamination of N-(adenyl-yl-9-alkanoyl)aminocarboxylic acids gives N-(hypoxanthinyl-9-alkanoyl)aminocarboxylic acids.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 126–130, January, 1985.     

Diffusion Sensor of Mechanical Signals: Frequency Response at High Frequencies

The frequency response of a diffusion transducer with gauze electrodes, studied theoretically at high frequencies, is proportional to ^-3/2 starting with = D/R ² at < /R ² and to ^-1 at > /R ². Here, = 2f, f is the signal frequency, the electrolyte viscosity, D a diffusion coefficient, and R the radius of the gauze filaments. The calculation is compared with experiment.     

On the synthesis of ω-appended hypericin derivatives

Summary A method for the preparation ofbis--appended hypericin derivatives bearingn-octyl,n-hexadecyl, and 2-(2-(2-hydroxyethoxy)-ethoxy)-ethoxymethyl substituents was developed. The key step — the synthesis of appropriately -substituted emodin derivatives — was achieved by solvolyzing 3-bromomethyl-1,6,8-triacetyloxy-anthracene-9,10-dione (-bromo triacetylemodin) in an appropriate alcohol in the presence of silver perchlorate. The correspondingbis--substituted hypericins were then prepared conventionally by dimerizing the -substituted emodin anthrones. The latter were prepared by reduction of the -appended emodins.

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Zur Synthese von -substituierten Hypericinderivaten

Zusammenfassung Eine Methode zur Darstellung vonbis--substituierten Hypericinderivaten wurde entwickelt. Der Schlüsselschritt — die Synthese der entsprechenden Emodinderivate — wurde durch die Solvolyse von 3-Bromomethyl-1,6,8-triacetyloxyanthracen-9,10-dion (-Bromtriacetylemodin) im entsprechenden Alkohol in Gegenwart von Silberperchlorat ermöglicht. Die entsprechendenbis--substituierten Hypericinderivate wurden auf konventionelle Weise durch Dimerisierung der -substituierten Emodinanthrone dargestellt. Letztere erhielt man durch Reduktion der -substituierten Emodine.

     

Reaction ofα,α-dichloro-ω-bromoalkanes andα,α-dichloro-ω-bromoalkenes with benzylmagnesium and allylmagnesium halides

Conclusions The,-dichloro--bromoalkanes and,-dichloro--bromoalkenes react with the benzyl- and allylmagnesium halides in tetrahydrofuran solution to give,-dichloroalkyl(alkenyl)benzenes,,-dichloroalkadienes in high yields. For all practical purposes the reactions do not go in ether.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 4, pp. 886–890, April, 1972.     

Synthesis of ω-haloalkanoic acids by the catalytic decomposition of cycloalkane hydroperoxides by copper ions

Conclusions The action of catalytic amounts of copper ions in the presence of MX salts (M=K and Na, X=Cl, Br, I, SCN) leads to the decomposition of the hydroperoxides of C₅-C₇ cycloalkanones with the formation of -chloro-,-bromo-, -iodo-, and -thiocyanoalkanoic acids.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 11, pp. 2628–2630, November, 1984.     

Synthesis of α, α, ω-trihydropolyfluoroalkyl chlorophosphates by the reaction between α,α,ω-trihydropolyfluoroalkyl phosphites and sulfuryl chloride

Conclusions An efficient method for the synthesis of ,,-trihydropolyfluoroalkyl chlorophosphates is by reacting ,,-trihydropolyfluoroalkyl dichlorophosphites and bis-(,,-trihydropolyfluoroalkyl) phosphites with sulfuryl chloride. It has been found that in three-coordinated polyfluoroalkyl phosphites, the high electronegativity of the polyfluoroalkyl groups hinders cleavage of the latter on reaction with sulfuryl chloride, thereby facilitating the formation of oxidation products.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 1, pp. 146–149, January, 1988.