Fracture analysis of annealed PVDF films

The effect of annealing 50 μm thick, extruded poly(vinylidene fluoride) films in form (-PVDF) was investigated by differential scanning calorimetry and mechanical testing on unnotched and double-edge notched tensile specimens. As to the fracture behavior, micromechanisms of cavitation, spherulite breakdown, fiber bundle structure formation and - to β-phase transformation were detected. The progressive structural evolution taking place during annealing affected the deformation and fracture behavior significantly. While the annealing-induced subtle distinctions in microstructure are slightly reflected by the determined mechanical and essential work of fracture (EWF) properties, a distinct differentiation was possible by analysis of the process zone. A correlation between characteristic values of the process zone at necking and the endothermic transitions due to secondary crystallization determined by differential scanning calorimetry (DSC) was established. Annealing of PVDF films facilitates the micromechanism of cavitation, which is presumably related to perfection of morphological superstructures (spherulites) and, thus, interspherulitic stress concentration and failure.     

Über den Einfluß der Kristallitlänge auf die Röntgen-Interferenzen der Polyamide

Ohne ZusammenfassungMit 7 Abbildungen.Derzeitige Anschrift des Verfassers: Bundeslehr- und Versuchsanstalt für chem. Industrie. Wien XVII, Rosensteingasse 79. Die Arbeit wurde 1944 durchgeführt. Herrn Prof. Dr.K. Heß spreche ich für die Aufnahme in sein Institut meinen verbindlichen Dank aus.     

Determination of naturally occurring radionuclides in selected rocks from Hetaunda area,central Nepal

The specific activities of the naturally occurring radionuclides ²³⁸U, ²³²Th, and ⁴⁰K were measured in rock samples from the Hetaunda area, central Nepal, using gamma spectrometry. The specific activities were found to be in the range of 17–95 Bq kg⁻¹ for ²³⁸U, 24–260 Bq kg⁻¹ for ²³²Th and 32–541 Bq kg⁻¹ for ⁴⁰K. From these data absorbed dose rates in air and annual effective doses were calculated and compared with respective data from the UNSCEAR compilation. The results from our study open the door to the safe applicability of most of the investigated materials as a cheep building material.     

Modeling anesthetic binding sites within the glycine alpha one receptor based on prokaryotic ion channel templates: the problem with TM4

Ligand-gated ion channels (LGICs) significantly modulate anesthetic effects. Their exact molecular structure remains unknown. This has led to ambiguity regarding the proper amino acid alignment within their 3D structure and, in turn, the location of any anesthetic binding sites. Current controversies suggest that such a site could be located in either an intra- or intersubunit locale within the transmembrane domain of the protein. Here, we built a model of the glycine alpha one receptor (GlyRa1) based on the open-state structures of two new high-resolution ion channel templates from the prokaryote, Gloebacter violaceus (GLIC). Sequence scoring suggests reasonable homology between GlyRa1 and GLIC. Three of the residues notable for modulating anesthetic action are on transmembrane segments 1-3 (TM1-3): (ILE229, SER 267, and ALA 288). They line an intersubunit interface, in contrast to previous models. However, residues from the fourth transmembrane domain (TM4) that are known to modulate a variety of anesthetic effects are quite distant from this putative anesthetic binding site. While this model can account for a large proportion of the physicochemical data regarding such proteins, it cannot readily account for the alterations on anesthetic effects that are due to mutations within TM4.     

Palladium-catalyzed coupling of allylboronic acids with iodobenzenes. Selective formation of the branched allylic product in the absence of directing groups

Palladium-catalyzed coupling reactions of functionalized allylboronic acids with iodobenzenes were achieved under standard Suzuki-Miyaura coupling conditions. The coupling reactions afforded selectively the branched allylic products in high to excellent yields. In contrast to palladium-catalyzed nucleophilic substitution reactions proceeding via (eta3-allyl)palladium intermediates, this process does not require directing groups in the allyl moiety to achieve substitution at the congested allylic terminus. The regioselectivity of the process was largely unaffected by the substituent effects of the iodobenzenes and the allylic substrates.     

Structure-Infrared Optical Property-Correlations of C,O,H-Polymers for Transparent Insulation and Greenhouse Applications

Summary. In this paper an understanding of the physical relationships between the material structure and the temperature dependent infrared optical properties of different transparent polymer films for solar applications is described. The infrared optical properties are relevant for the heat transport of e.g. greenhouse and transparent insulation structures. The properties were determined based on infrared transmittance measurements and the assumption of a constant index of refraction from the visible range. To establish structure-property-correlations molecular structure parameters such as the concentration of carbon-oxygen single bonds and carbon-hydroxyl groups were determined. For 50 μm thick films a good correlation between the concentration of the functional carbon-hydroxyl and the carbon-oxygen group and the infrared optical thickness as well as the hemispherical emittance was found. This correlation fits well for high and low infrared radiation absorbing polymeric materials consisting of carbon, hydrogen, and oxygen atoms. The carbon-hydroxyl group appears to be slightly more effective than the carbon-oxygen single bond. Interestingly, the correlation works for polymers with aromatic (PC, PET) and aliphatic (PMMA, CTA, ethylene copolymers) groups.     

Effect of Material Structure and Additives on the Optical Properties of PP Cast Films

Polypropylene homopolymer and ethylene/propylene-random-copolymer cast films formulated with slip, anti-blocking, and acid scavenger aids were analyzed as to material structure and optical properties. The structural and topographical characterization was done by atomic force microscopy and by spectroscopic methods. Optical properties were determined using a hazemeter and an UV/VIS/NIR spectrophotometer. As to the effect of additives it was established that slip and anti-blocking aids migrate to and accumulate on the surface, resulting in increased surface roughness and larger scattering identities close to the surface. Acid scavenger additives were shown to contribute to less significant slip aid domains and hence to lower haze. In general, films without additives showed much better optical properties. The separation of haze into its bulk and surface components revealed that the total haze is dominated by surface haze.     

Semi-Discrete Isothermic Surfaces

We study mappings of the form ${x : \mathbb{Z}\times\mathbb{R}\to\mathbb{R}^3}$ which can be seen as a limit case of purely discrete surfaces, or as a semi-discretization of smooth surfaces. In particular we discuss circular surfaces, isothermic surfaces, conformal mappings, and dualizability in the sense of Christoffel. We arrive at a semi-discrete version of Koenigs nets and show that in the setting of circular surfaces, isothermicity is the same as dualizability. We show that minimal surfaces constructed as a dual of a sphere have vanishing mean curvature in a certain well-defined sense, and we also give an incidence-geometric characterization of isothermic surfaces.     

Evaluation of a sensitive,reasonable, and fast detection method for 55Fe in steel

Journal of Radioanalytical and Nuclear Chemistry - A pilot study to quantify 55Fe in steel from a reactor vessel of a nuclear power plant by accelerator mass spectrometry (AMS) without any chemical...