X-ray diffraction and morphology of crystalline,hard, elastic materials

Summary X-ray diffraction and electron microscopic results on several crystalline polymers which demonstrate elastic properties (polypropylene, Celcon^®, poly-4-methyl-pentene) are reported. Photographic small angle X-ray diffraction techniques provided considerable qualitative information, concerning the morphological features of these elastic materials both as extruded, annealed and during extension. Lamellar thickness, thickness distribution and perfection of lamellae could be estimated. Lateral order features and orientation of the lamellar structures were obtainable from the sharpness and length of the equatorial wide angle diffraction arcs. Electron microscopic results essentially confirm the morphological features postulated on the basis of the X-ray results. These morphological features are discussed in terms of a general structural model which appears consistent with the mechanical properties of these materials.

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Zusammenfassung Röntgenbeugung und elektronenmikroskopische Daten von einigen kristallinen Polymerprodukten mit elastischen Eigenschaften (Polypropylen, Celcon, Poly-4-methylpenten) werden berichtet. Die photographische Röntgen-Kleinwinkelmethode liefert wichtige qualitative Messungen der morphologischen Struktur dieser elastischen Materialien in den Zuständen sowohl wie hergestellt als auch nach Tempern und während des Dehnungsprozesses. Die Dicke der Lamellen, ihre Dikkenverteilung und die Güte der Lamellen konnten abgeschätzt werden. Die laterale Ordnung und die Orientierung der Lamellen kann aus Weitwinkelbeugungsdaten abgeleitet werden. Die Elektronenmikroskopie bestätigt die Morphologie, die aus Röntgendaten folgt. Ein allgemeines Strukturmodel dieser Morphologie, das im Einklang mit den mechanischen Eigenschaften dieser Produkte steht, wird diskutiert.

     

Facile Total Synthesis of (±)‐Nimbiol

A facile total synthesis of (±)‐nimbiol 1 has been achieved. In order to decrease the dioxo byproduct 2a , an improved oxidation system of CrO₃/H₂O/HOAc/NaOAc was used.     

Sensitivity in Supramolecular Architectures of Polyaromatic Salts Containing Two Singly‐Pimerized Bipyridines

Three novel supramolecular arrays of zigzag polyaromatic salts are reported. Both the conformation and disposition of the dications are subjected to various noncovalent interactions. Thus, the presence or absence of the π‐π interacting enclathrated molecules, the efficient packing and the involved hydrogen bonding interactions of anions, as well as the increased hydrophobic property of the dications themselves exert influence.     

Isolierung und Struktur von Pteridinen (Lumazinen) aus Russula sp. (Täublinge; Basidiomycetes)

Isolation and Structure Elucidation of Pteridines (Lumazines) from Russula sp. (Basidiomycetes) Extensive chromatogaphic separations and spectroscopic investigations have led to the isolation and identification of several water-soluble pteridines from Russula sp., the so-called russupteridines, namely: 1-(5-amino-2-6-dioxo-1,2,3,6-tetrahydeopyrimidin-4-yl)amino-1-deoxy-D -ribitol ( 1 ; a pro-lumazine; first identification in a basidiomycete(; l-deoxy-l-(6-methyl-2-4,7-trioxo-1,2,3,4,7,8-hexahydro-pteridin-8-yl)-D -ribitol ( 3 ) and l-deoxy-1-(2,4,7-trioxo-1,2,3,4,7,8-hexahydeopteridin-8-yl)-D -ribitol ( 4 ); both compounds found for the first time in higher fungi; they belong to the components with the strongest violet-blue fluorescence in Russula sp.; riboflavine ( 6 ; now recognized as an important yellow colorant in a great many of Russula sp.); russupteridine-yellow I (= l-(6-amino-7-(N-fromylimino)-2,4-dioxo-1,2,3,4,7,8-hexahydropteridin-8-yl)-1-deoxy-D -ribitol; 5 ; a component with very strong fluorescence; the first derivative of the novel 6,7-diamino-lamazine); russupteridine-yellow IV (= l-deoxy-1-)(2,6,8-trioxo-2,4,5,6,7,8-hexahydro-1H-imidazolo[4,5-g]pteridin-4-yl)-D -ribitol (7)). Two further yellow russupteridines (yellow II and Yellow V) with very strong fluorescence have been isolated and characterized.     

Cyclisierungsreaktionen zu Pyrano[3,2-c]pyridinen und pyrano[3,2-c]chinolinen unter Verwendung von Ethoxymethylen-malodinitril bzw.-cyanessigester Synthesen mit Nitrilen, 50. Mitt. pyrano[3,2-c]quinolines with ethoxymethylene-malonitrile and-ethyl cyanoacetate,resp.

Reaction of ethoxymethylene-malonitrile and ethoxymethyleneethyl cyanoacetate, resp., with 4-hydroxy-2-pyridones (1a–b) and 4-hydroxy-2-quinolones (3a–b) leads to 2,5-dioxo-5,6-dihydro-2 H-pyrano[3,2-c]pyridine-(2a–d) and 2,5-dioxo-5,6-dihydro-pyrano[3.2-c]quinoline-derivatives (4a–d), resp.2a–d and4a–d exhibit remarkable visible fluorescence. Absorption- and emmission-data in different solvents are reported.     

The Nitrosation of Primary Aliphatic Diazocarbonyl Compounds: Formation of α-carbonyl nitrile oxides. Preliminary communication

Aqueous nitrosation of primary α-carbonyl diazo compounds (ethyl diazoacetate, diazoacetone, diazoacetophenones) yields α-carbonyl nitrile oxides, R? CO? CNO; their formation is demonstrated by 1,3-dipolar addition reactions.     

Studies on Chemical Constituents of Polygonum Ciliinerve Ohwi

Three new apianen lactones Maomailiaoine I ( 1 ), Maomailiaoine II ( 2 ) and Maoimaliaoine III ( 3 ), together with one known apianen lactone, five known flavonoids and three other known compounds were isolated from Polgonum ciliinerve Ohwi. Their structures were deduced from spectroscopic methods and 2D NMR techniques.     

Theoretical Study on the Structures and Stability of Isomers and Complex of[Si,C,O,O] Sytem

A detailed singlet potential energy surface(PES) of [Si,C,O,O] system including a van der Waals (vdW) comples SiO……CO2,eight isomers,and twelve transiton states is investigated by MP2 and QCISD(T) (single-point)methods.At the final QCISD(T)/6-311 G(2df)//MP2/6-311G(d) level with zero-point energy included,the complex SiO……CO is found to be thermodynamically and kinetically the most stable species.Although eight ismoers are located as local energy minima,they are rather unstable toward isomerization to the dissociation fragments or comples.For the reaction of silocon atoms with carbon dioxide,two competitive reaction channels are found,and the primary pathway,which leads to the products of SiO and CO fragments,is the direct oxygen-abstraction process from carbon dioxide by silicon atom with a41.16 kJ/mol reaction barrier height.Our predications are in good agreement with previous experimental and theoretical studies.     

Über eine zum Kreisproblem verwandte Summe

An equivalent form of the classical circle problem is the unproved conjecture (3) . In this note the corresponding conjecture with _k (.) (the 1-periodic Bernoulli polynomials of orderk2) instead of ₁(.) is settled in an affirmative way (even with =0). Moreover, a generalized sum (6) is estimated by means of an analogue to a classical result due tovan der Corput.