Thermal analysis and X-ray studies of chiral ferroelectric liquid crystalline materials and their binary mixtures

Summary Thermal properties of a homologous series of ferroelectric liquid crystals S-(-)-[4-(2-n-alkoxy-propionyloxy)]biphenyl-4'-[n-alkoxy-(3,5-dimethyl)]benzoate have been investigated by polarizing optical microscopy and differential scanning calorimetry. The mesophases were identified and confirmed by X-ray too. Three binary mixtures were prepared from the individual homologues. In one of the mixtures (Mix1), the ferroelectric SmC* phase has broadened and became enantiotropic. This mesophase remained monotropic in the other two mixtures (Mix2, Mix3). The chiral nematic N* phase did not appear in Mix1, but remained monotropic for the other two mixtures. Two molecular parameters, the layer spacing and the average intermolecular distance have been calculated from the X-ray results for the homologues and their mixtures. An intercalated tail-to-tail packing of molecules was found both in the single compounds and their mixtures resulting in the layer spacing about half of the molecular length of the single compounds.     

The influence of tensile stress on grain and cell boundary precipitation in supersaturated Al-Zn alloys during creep

The results are presented of the optical microscopic and X-ray diffraction study of the stress-induced nucleation and growth of (Zn) precipitates at grain and cell boundaries (GB's and CB's) during uniaxial creep at 200 °C of supersaturated AlZn20 and AlZn30 alloys. The rate of precipitation is increased mainly owing to the modifying effect of tensile stress on diffusion processes in alloy samples during their anneal. The diffusion of Zn atoms toward GB's and CB's from adjacent regions of grains is accompanied during creep by diffusive flux of Zn along boundaries parallel or nearly parallel to the tensile creep axis toward boundaries with near to normal orientation to that axis. Enhanced precipitation of results then preferentially at the latter and is supressed at the former boundaries where even the dissolution of preexisting has been found during a later application of tensile stress. The stress-induced precipitation of at GB's gradually ceases with prolonged creep exposures due to the lengthening of duffusion paths of Zn atoms from grain interior to GB's.Dissolution of lamellae by their regress toward GB's and CB's is assisted with the stress-induced diffusion of Zn along epitaxial / lamellar interfaces. Copious precipitation of at the parts of GB's and/or CB's with near to normal orientation to the creep axis is then observed on account of Zn from dissolved lamellae. Creep strain also leads to the fragmentation of lamellae and thus also to breaking down of the paths for diffusion of Zn along / interfaces. Spheroidization of fragmented parts of lamellae is then observed. Spheroids of remain embedded within the former lamellar regions.Large creep strains and high strain rates observed on fine-grained alloy samples may be associated with an enhanced viscous GB sliding due to the stress-dependent flow of Zn along GB's and/or CB's.     

On kinetics of the photodissociation iodine laser

The kinetics of iodine laser amplifiers is examined by solving the time evolution equations of chemical kinetics during optical pumping. The pumping radiation intensity is modelled by a black body of the temperature varying in time (corresponding to the flash lamp pulse). A brief comparison is made of pumping effects by long and short light pulses. Pumping by the long pulse is studied in more detail and it is found that there exists an optimum pulse strength beyond which the inversion in the laser mixture no longer grows appreciably, only its lifetime is shortened. In this connection the effect of pyrolysis of the alkyliodide molecule is also discussed. The pyrolysis is found to occur under very strong illumination, but it does not interfere with the photolytic decomposition and the optimum laser action. Finally, the influence of the reaction rate constants is studied in a systematic way and only few of them are found to carry real weight.The authors are obliged to Drs. S. V. Kuznetsova and A. I. Maslov who were consulted on the values of the reaction constants and who also drew our attention to some of the references.     

Electrical properties of some crystalline salts of adenine

In the present paper we report the first experimental results on ac and dc conductivity and permittivity of adenine hemisulphate hydrate and adenine sulphate measured at atmospheric and high hydrostatic pressures. For both materials ac conductivity is of ^s type, where:s 1·1· Room temperature dc conductivity of adenine hemisulphate hydrate equals approximately 5×10^{–15 –1} cm^–1 with an activation energy of 0·86 eV; dc conductivity of adenine sulphate is less than 10^–16 cm^–1. On the basis of these measurements and those carried out at high pressure, it is concluded that conductivity of adenine hemisulphate hydrate is of electronic type.The authors wish to thank Dr. J. Zachová for the preparation of adenine salts single crystals.     

Synthesen in der Pyridazin-Reihe, 26. Mitt.:

Zusammenfassung Es wird über die Synthese von verschiedenen methylsubstituiertens-Triazolo[4,3—b]pyridazinen berichtet. Außerdem wurdens-Triazolo[4,3—b]pyridazin und seine 7-Methyl- und 6-Chlor-Derivate der homolytischen Methylierung unterworfen, die Reaktionsgemische gaschromatographisch auf einzelne Methyl-s-triazolo[4,3—b]pyridazine aufgetrennt und die Verbindungen identifiziert.

---

Syntheses of pyridazines, XXVI: Synthesis and homolytic methylation of s-triazolo[4.3—b]pyridazines

The syntheses of some methyl substituteds-triazolo[4,3—b]-pyridazines are reported.s-Triazolo[4.3—b]pyridazine and its 7-methyl and 6-chloro analogs were submitted to homolytic methylations and the obtained reaction mixtures were separated by gas chromatography into particular components which were then identified.

     

Spektroskopische Untersuchungen der Metallkomplexe des 2,5-Dibenzoyl-3,4-dihydroxyselenophens

Zusammenfassung Eine Reihe von Metallkomplexen des 2,5-Dibenzoyl-3,4-dihydroxy-selenophens wurden spektroskopisch untersucht. Das Verhalten des Wismutkomplexes und die Möglichkeiten einer spektrophotometrischen Wismutbestimmung auf diesem Wege wurden eingehend studiert.

---

Summary A spectroscopic examination was made of a series of metal complexes of 2,5-dibenzoyl-3,4-dihydroxyselenophen. The behavior of the bismuth complex and the possibilities of a spectrophotometric method of determining bismuth in this manner were studied thoroughly.

---

---

Herrn Univ.-Prof. Dr.Hans Lieb zum 80. Geburtstag gewidmet.     

In Situ Amperometric Detection of Vesicles and Microgel Phases in an Aggregating System: Calcium Alginate

In situ amperometric characterization of an aggregating system in terms of molecular adsorption and single microparticle interactions at the electrode interface is demonstrated using a model system: alginate/Ca(II) in an aqueous electrolyte solution. Recording of chronoamperometric curves of oxygen reduction at the dropping mercury electrode is designed for detection of dip‐shaped signals of individual gel microparticles. By addition of Ca(II) decrease of alginate adsorption is accompanied by appearance of signals indicating vesicle type association of alginate molecules and microparticles of gel phase. AFM imaging provided evidence of initial stage in calcium alginate gel formation.     

Photochemistry of condensed isoxazolines

Summary The condensed bridged isoxazolines4 are rearranged on irradiation with a low-pressure mercury lamp exclusively into condensed derivatives of tetrahydropyridine5. The selectivity of the rearrangement is due to a stabilization of the biradical8 by the overlap of the radical-electrons with -electrons of the C=C double bond and the heterocyclic ring. Quantum yields of the photorearrangement, established from the consumption of the starting materials4, were determined.

---

Photochemie kondensierter Isoxazoline

Zusammenfassung Die kondensierten überbrückten Isoxazoline4 werden durch Bestrahlen mit einer Niederdruckquecksilberlampe ausschließlich zu kondensierten Tetrahydropyridinderivaten (5) umgelagert. Die Selektivität der Umlagerung beruht auf der Stabilisierung des Diradikals8 durch Überlappung der ungepaarten Elektronen mit -Elektronen der C=C-Doppelbindung und des Heterocyclus. Aus dem Verbrauch an Ausgangsmaterial (4) wurden Quantenausbeuten der Photoumlagerung bestimmt.

     

Statistical investigations of some element distributions in healthy and pathologically altered human colon mucosa

In this paper data are presented concerning the distribution of Cr, Sb, Sc, Fe, Co, and Zn in HCM, of patients with histopathologically and clinically verified findings: Healthy—N; Colitis Chronica-CCh; Colitis Ulcerosa-CU; Adenoma Tubulare-AT; Adenocarcinoma-ACa. The data are presented on the basis of the contents of elements (C_E parameter expressed in nkg/g of lyophilized HCM) obtained by INAA and calculated by computer programs, with statistical parameters (n, XBAR, XMIN-XMAX, R, V, SE and SDEV). The values of C_E parameters of elements found in all diagnostic groups (decreasing order) are also presented. The minimal \(\bar C_E \) parameters for all elements except Zn are found in diagnostic groups AT and ACa. The maximal differences of \(\bar C_E \) parameters in DS-decreasing orders are found for Sb (78.89%) and the minimal for Zn (18.89%).