Slip-step on polyoxymethylene crystals

Crystals of polyoxymethylene have been grown from solution in bromobenzene. In many growth features, which are similar to those for monomeric crystals, the movement of dislocation can be traced by a slip-step raised in the growth surface. Such slip-steps are associated with single spirals, two spirals of opposite senses and two spirals of the same sense. Anomalies in the growth patterns of crystals have also been observed and attributed to the movement of screw dislocation long before the cessation of growth.     

Synthesis and characterization of bromoquinazolinone substituted spiro[isobenzofuran-1,9′-xanthene]-3-ones

Some new bromoquinazolinone substituted fluoran compounds were synthesized by the reaction of the keto acid, 2-(4-diethylamino-2-hydroxybenzoyl)benzoic acid with different 3-(3/4-hydroxyphenyl)-2-methyl/phenylbromo-4(3H) quinazolinones in the presence of a dehydration condensing agent like sulfuric acid. Various quinazolinones were prepared by reacting different monobromo/dibromobenzoxazine-4-ones with 3-aminophenol or 4-aminophenol in the presence of pyridine as a solvent. All the synthesized fluoran compounds were identified by conventional methods such as melting point, IR, ¹H NMR, ¹³C NMR, elemental analysis and UV-visible spectroscopy in organic solvents and 95% acetic acid. All these colorless fluorans develop a color in contact with electron accepting compounds.     

Synthesis and thermal stability of xylene-formaldehyde resins

o-,p- andm-xylene have been condensed with formaldehyde using paratoluene sulphonic acid as a catalyst and acetic acid/acetic anhydride as a solvent. The xylene-formaldehyde resins thus obtained have been characterised by IR and NMR spectra. The average molecular weight of the resin samples was determined by vapour pressure osmometry. Kinetic parameters were determined by differential thermal analysis, thermogravimetry and differential scanning calorimetry.     

Crystallization of polyacrylonitrile: Growth mechanisms for various growth features

Summary Crystallization of polyacrylonitrile has been carried out at different temperatures from fractionated sample, and different morphological growth features obtained are compared with those observed previously from unfractionated sample. Several new growth features like rectangular single crystals, twinned crystals, ovals and spherulites have been observed. The role of different typical growth features for the development of spherulites has been studied. It seems that the proposed growth mechanism for the development of spherulite grown either from the melt or concentrated solution is the same for different polymers. From the observed growth features of dendritic nature in different conditions, a mechanism of development of dendritic spherulite is discussed.

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Zusammenfassung Die Kristallisation von Polyacrylnitril und anderen Polymeren wird nach der Methode der Filmbildung ausgeführt. Das Polyacrylnitril war hergestellt durch Polymerisation von Acrylnitril initiiert mit einem Cer-Ionen-Redoxsystem. Die Fraktionierung des Polyacrylnitrils wurde mit der Methode, dieKobayashi undFujisaki beschrieben haben, durchgeführt. Die vorliegende Studie für die Untersuchung der wachsenden Kristalle wurde an einer Probe mit dem mittleren Molekulargewicht durchgeführt. Cellulosetriacetat (CTA) mit dem Molekulargewicht , bestimmt aus Viskositätsmessungen in Chloroform bei 25 °C nach Haward und Parikh, wurde ebenso wie Polydthylen (PE), mit aus Viskositdtsmessungen in Xylol bei 90 °C nach Billmeyer, für die Beobachtung des Kristallwachstums verwendet. PE wurde von den Chemischen Werken Hüls (Deutschland) geliefert, CTA durch Acetylierung von Cellulose mit Essigsdure und Essigsäureanhydrid und Perchlorsäure als Katalysator präpariert. Amyloseacetat wurde aus Amylose extrahiert, aus Kartoffelstärke gewonnen.

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With 20 figures     

A study of protein synthesis in cells cultured from involved psoriatic skin

Using histochemical techniques an abnormal programme of epidermal differentiation has been well documented in psoriasis. In order to characterise further the biochemistry of this process we have cultured dermal fibroblasts and epidermal keratinocytes from involved psoriatic skin. This has facilitated metabolic radiolabelling of skin cells and analysis of protein synthesis by two-dimensional polyacrylamide gel electrophoresis. The expression of keratin and differentiation markers was identical to that of normal keratinocytes, suggesting that psoriatic epidermal differentiation is not truncated in vitro as has been postulated to be the case in vivo. Low molecular mass components (5-8.5 kDa), previously shown to be upregulated in suprabasal keratinocytes, were detected in epidermal fractions from psoriatic skin enriched for basal cells. Of special interest was a component of 26 kDa, pI 5.9, which was highly upregulated in psoriatic as compared to normal cultured keratinocytes and was not detected in fibroblasts. These findings are in accord with a qualitatively abnormal pattern of differentiation for keratinocytes in the involved psoriatic epidermis.     

Graphite furnace-atomic absorption spectrophotometric determination of palladium in soil

A new and sensitive procedure for the graphite furnace-atomic absorption spectrophotometric (GF-AAS) determination of Pd in soil at nanogram level is described. The method is based on prior separation and enrichment of the metal as Pd(II)-SnCl3- -N-butylacetamide (BAA) complex into 1-pentanol (PN) by solvent extraction method. The value of the molar absorptivity of the complex in three solvents, i.e. ethyl acetate, 1-pentanol, chloroform, lie in the range of (0.70-2.75) x 10(4) L mol(-1) cm(-1) at lambda(max) 360-440 nm. The metal could be enriched into organic solvent, i.e. PN, up to 10-folds. The sensitivity (A = 0.0044) of the method in the term of the peak height was 0.5 ng Pd/mL of the aqueous solution at an enrichment factor (EF) of 5. Optimization of analytical variables during enrichment and GF-AAS determination of the metal are discussed. The method has been applied for the analysis of Pd to soil samples derived from roads and highways in Germany.     

Transition metal polymeric chelates: Spectral, magnetic, thermal behaviour of polymeric chelates of poly(resacetophenone diyl ethylene)s with Ni(II), Cu(II), Mn(II), Zn(II) and Co(II)

Polymeric chelates of the type [ML₂]_n where M = Ni(II), Cu(II), Zn(II) or Co(II), L = poly(resacetophenone diyl ethylene)s, andn= degree of polymerization, have been synthesized. Their structures have been elucidated on the basis of analytical, magnetic, electronic and IR spectral studies. Electronic spectra in conjunction with magnetic moments are in accord with an octahedral environment around the central metal ion in all polymeric chelates except Cu(II) and Zn(II) polymeric chelates which have been shown to possess square planar and tetrahedral geometries, respectively. IR spectral studies further suggest that the metal ions are coordinated through the oxygens of the carbonyl and the phenolic hydroxyl groups. All the chelates are paramagnetic except Zn(II), which is found to be diamagnetic.     

Postcolumn formation of fluorophores from nitrogenous pesticides by UV photolysis

The ultraviolet (UV) photolysis of several classes of nitrogenous pesticides was examined with a view to photo-induced fluorescence detection in flow-injection analysis (FIA) and liquid chromatography. The solvents evaluated as typical reversed-phase mobile phases included water, methanol, and 1:1 mixtures of methanol/water and acetonitrile/water, and methanol/acetonitrilelwater mixtures. Acetone, acetophenone, the surfactant triton X-100, and the photocatalyst titanium dioxide were assessed as photosensitizers to enhance the UV photolysis and fluorescence responses. FIA and liquid chromatographic separations of several pesticides were followed by post-column UV photolysis for the fluorescence detection. Ultraviolet photolysis produces some fluorescent products. The type of photolytic solvent seems to play a significant role. The presence of photosensitizers also affects the fluorescence response of some pesticides. The photochemical transformation products of some of the pesticides are suggested. Analytical figures of merit were evaluated for determination of several pesticides in ground water. The post-column UV photolysis approach for fluorescence detection in liquid chromatography was assessed for several nitrogenous pesticides in ground water samples at ng/g concentrations.     

Synthesis and characterization of thermally stable poly-N, N′-arylenebismaleimide

Three N,N′-arylenebismaleimides, viz. N,N′-m-phenylenebismaleimide, N,N′-p-phenylenebismaleimide and N,N′-benzidinebismaleimide, were prepared and polymerized in toluene using benzoyl peroxide (BPO) as initiator. The polymers obtained were characterized on the basis of elemental analysis and IR spectra. The polymers are insoluble in common organic solvents. The thermal behaviour of these polymers was studied by DTA and TG methods and the kinetic parameters order of reaction and activation energy were estimated.