Study of thermal currents in powder β-spodumene ceramics doped with Cuo, FeO and TiO2

Ternary-phase ceramic system of Li₂O Al₂O₃ 4SiO₂ doped with CuO, FeO and TiO₂ has been prepared and subjected to dc electrical conductivity and thermally stimulated depolarization current (TSDC) measurements as a function of temperature (30-250 °C) and field strength. The electrical conductivity results are explained by assuming both ionic and electronic conduction mechanisms coexist with different contributions over the whole temperature range of experiments. TSDC spectra have been found to be characterized by a broad intense relaxation peak, which can be attributed to an ionic charge polarization. The broad relaxation transitions are apparently a result of the nonuniform nature of this process. Activation energies are calculated for both dc electrical conductivity and TSDC according to Arrhenius equation and initial rise method, respectively.     

Large Scale Linear Programs and Heuristics for the Design of Survivable Telecommunication Networks

We consider the problem of providing a minimum cost multi-service network subject to one link failure scenarios. We assume our network is fully meshed and demand is satisfied by using direct or two hop-paths. We provide a large scale linear programming formulation and propose and test two effective heuristics.     

Composting and biodegradation of thermally processed feather keratin polymer

Proteins obtained from agricultural sources represent a unique feedstock from which to prepare thermally processable polymers. In this study, thermally processed feather keratin films were composted with three-month-old compost inoculum in self-heating laboratory composters for 30 days and temperature and carbon dioxide development monitored. About 24% of the available carbon in the feather keratin polymer (FKP) was metabolized in this time and this may not be high enough for some applications. Degradation of the feather keratin polymers was observed within 10 days with concurrent molecular weight reduction measured using FT-IR. Visual inspection of the polymers also showed destruction of the films. A change in crystallinity was observed in DSC analysis and some degradation processes could be inferred from this as well.     

The mass spectra of 2-alkyl N-methyl pyrrolidines

The mass spectra of a series of 2-alkyl N-methyl pyrrolidines have been examined and fragments which may be pyrrole type structures are apparent. These ions are most prominent in the spectra of the long chain alkyl derivatives.     

Aliphatic Liquid Crystals with Positive Dielectric Anisotropy

Cyanothyl-subsituted cylohexyl cyclohexanoates, bi(cyclohexanes) and phenyl cyclohexanes were synthisized. Their mesmorphic behaviour is compared to that of the corresponding cyano derivatives. (Cyanoethyl)cyclohexyl cyclohenxanoates show mesmorphic properties in contrast to the corresponding cyano derivative. Separation of the cyano substituent from the rigid core of an anisotropic aliphatic compound by methylene groups enhances the thermodynamic stability of the mesophase. In aromatic compound, the cyanoethyl group leads to lower clearing points. These phenomena are attributed to teh influence of steric effects on the packing density and to the dependence of the clearing point on molecular association.     

Solochrome Violet R als Reagens zur spektrophotometrischen Bestimmung von Mikrogrammengen Molybd?n

Zusammenfassung In der vorliegenden Arbeit wird eine rasche und genaue spektrophotometrische Bestimmung von Mikrogrammengen MolybdÄn beschrieben. Als Reagens wird der Azofarbstoff Solochrome Violet R verwendet. Dieser bildet mit MolybdÄn in sehwach salzsaurem Medium einen rotgefÄrbten Komplex, der selbst bei Anwesenheit von ÄDTA bestÄndig ist. Dadurch ist es möglich, den störenden Einflu\ anderer Ionen, z. B. den des Zirkoniums, auszuschalten. Mit dieser Methode lassen sich noch 2,0 g MolybdÄn/10 ml Me\lösung mit relativ hoher Genauigkeit bestimmen.Wir danken Herrn Prof. Dr. F. Hecht für seine Unterstützung, die für das Zustandekommen dieser Arbeit von gro\em Nutzen war.     

Synthesis of heterocycles. Part II. New routes to acetylthiadiazolines and alkylazothiazoles

Methylglyoxalyl chloride arylhydrazones (III) react with an ethanolic solution of thiourea to give 2-amino-4-methyl-5-arylazothiazoles (XII) instead of the expected 2-acetyl-4-aryl-5-imino-Δ²-1,3,4-thiadiazolines (V) which were obtained from III and potassium thiocyanate. 3-Thiocyanato-2,4-pentanedione (IV) coupled with diazotized anilines to give V. The postulated routes to formation of V and XII from III are given. Nitrosation of V gave the corresponding N-nitroso derivatives (VI) which decomposed upon refluxing in dry xylene to give 2,4-disubstituted-Δ²-1,3,4-thiadiazolin-5-ones (VII). Boiling of either V or VI with hydrochloric acid gave the hydrochloride salt (VIII). The thiadiazolines V gave the respective N-acyl derivatives (IX) and (X) with acetic anhydride and benzoyl chloride in pyridine.     

Synthetic approaches towards bisspiro[naphthalene-2(1H),3′-(3H)pyrazol]-1-one-containing compounds

1,3-Dipolar cycloaddition reaction of bis{[4-(3,4-dihydro-(2H)-naphthalen-1-oxo-2-yl)methyl-idenephenyl]oxy}alkanes with nitrilimines (generated in situ by triethylamine dehydrohalogenation of the corresponding hydrazonoyl chlorides) in refluxing dry benzene afforded a mixture of monocycloadduct and dicycloadduct products in high regioselectivity. On the other hand, reaction of bis{[2-(3,4-dihydro-(2H)-naphthalen-1-oxo-2-yl)methylidenephenyl]oxy}alkanes with nitrilimines gave the corresponding dicycloadducts as the only isolable regioisomers.