Molecular dynamics in precision deuteriomethyl branched polyethylene from solid-state deuterium NMR

Deuterium quadrupolar echo NMR was applied to precision CD₃ branched polyethylene at temperatures ranging from below the glass transition up to the melting point. The CD₃ branches were placed on every 15th or 21st carbon with zero variation in the branch spacing by acyclic diene metathesis polymerization chemistry. The deuterium lineshapes were simulated and fit to the experimental spectrum assuming appropriate models that approximate the motions in the amorphous and crystalline phases. Spectral contributions of each phase were isolated by T₁ fitting. The fitting results comprise the isotropic reorientation correlation time distribution and axial jump angle distribution in these two phases, respectively. The mean jump angle was found to increase monotonically with temperature, approaching 35° near the melting point, consistent with previous carbon-13 NMR results on this same polymer.     

“Empowering” Cardiac Cells via Stem Cell Derived Mitochondrial Transplantation- Does Age Matter?

With cardiovascular diseases affecting millions of patients, new treatment strategies are urgently needed. The use of stem cell based approaches has been investigated during the last decades and promising effects have been achieved. However, the beneficial effect of stem cells has been found to being partly due to paracrine functions by alterations of their microenvironment and so an interesting field of research, the “stem- less” approaches has emerged over the last years using or altering the microenvironment, for example, via deletion of senescent cells, application of micro RNAs or by modifying the cellular energy metabolism via targeting mitochondria. Using autologous muscle-derived mitochondria for transplantations into the affected tissues has resulted in promising reports of improvements of cardiac functions in vitro and in vivo. However, since the targeted treatment group represents mainly elderly or otherwise sick patients, it is unclear whether and to what extent autologous mitochondria would exert their beneficial effects in these cases. Stem cells might represent better sources for mitochondria and could enhance the effect of mitochondrial transplantations. Therefore in this review we aim to provide an overview on aging effects of stem cells and mitochondria which might be important for mitochondrial transplantation and to give an overview on the current state in this field together with considerations worthwhile for further investigations.     

Self-stimulation of preoptic and lateral hypothalamus during behavioral thermoregulation in the albino rat.

Explored self-stimulating behavior in 5 male albino rats under ambient temperatures of 2, 12, 25, and 35.C while radiant-heat reinforcement was concurrently available. Preoptic self-stimulation was accompanied by hypothermia even at neutral temperatures, and in the cold, preoptic self-stimulation behavior was maintained alternating with the use of the heat-lamp lever. Conversely, self-stimulation of the lateral hypothalamus produced hyperthermia at neutral temperatures. In the cold, lateral hypothalamic self-stimulation was suppressed, although maintained sufficiently to preserve normal body temperatures without use of the heat lamp. High-temperature stress suppressed both preoptic and lateral hypothalamic self-stimulation. The interpretation suggests that electrical stimulation of the preoptic area signals a pseudowarmth state which results in activation of heat-loss mechanisms. (15 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Advanced Processing and Properties of Thixotropic Formed Components Based on Partially Melted Magnesium

Contrary to the manufacture of aluminium components in the semi‐solid, thixotropic state the production of magnesium based components by semi‐solid techniques is still uncommon. For this reason, the advantage of this production method is analysed with regard to the commercial magnesium alloy AZ80. The objective of this research is semi‐solid‐casting (SSC) of AZ80 for the production of a light weight component in near‐net‐shape quality and with advanced properties. Using extruded primary feedstock material, the behaviour and the advantages are investigated. Billets with a weight of up to 2 kg are heated up into a semi‐solid state. To avoid any risk of self‐ignition of the material an automatic, temperature controlled induction heating system is used. To achieve an optimum homogeneous grain structure the induction heating power is varied making use of a process control system based on power‐time‐curves. The heated billets are transported in the soft semi‐solid condition from the induction heating system to a die casting machine to produce components with wall thickness’ between 2 and 10 mm. After forming of the components, the influence of heat treatment on the grain structure and especially on the mechanical properties is determined to provide parts with optimised characteristics. To compare the properties of the special globular grain and microstructure, the results of various static and dynamic tests are analysed. It is found that components can be manufactured with a magnesium alloy in a thixotropic state in near‐net‐shape quality, with low porosity and with excellent mechanical properties like elongation of up to 15%.     

The impact of zinc neutralization on the structure and dynamics of precise polyethylene acrylic acid ionomers: A solid-state 13C NMR study

Solid-state ¹³C NMR experiments were performed on a series of linear poly(ethylene-co-acrylic acid) (E-AA) copolymers with the carboxylic acid group spaced precisely or randomly along the polyethylene backbone in order to determine the impact that molar percent acid content and acid group spacing have on the structure and dynamics of these materials. The impact of Zn-neutralization is investigated in precise E-AA ionomers. ¹³C cross-polarization (CP) NMR experiments with ¹H dipolar or ¹H spin-lock filters were utilized to identify the amorphous or crystalline components in the materials. Constraints extracted from the filtering experiments were used to fit quantitative NMR data for samples that contained both crystalline and amorphous regions. All random copolymers contained crystalline phases, while only the precise sample with the longest polyethylene run between acid groups (twenty CH₂ groups) contained a crystalline component. The crystalline phase in this precise copolymer decreased with increasing zinc content.     

Investigating the degradation resistance of silicone-acrylate containing automotive clearcoats exposed to bird droppings

This work reports preparation of acrylic/melamine based clearcoats containing various loads of a reactive polysiloxane additive. The additive was incorporated into the clearcoat formulations up to 8 wt% to enhance its resistance against bird droppings. Contact angle measurements, ATR spectroscopy, energy dispersive X-ray analysis, appearance measurements together with different microscopic techniques were utilized to reveal the effects of additive on the properties of the coating prior and after exposure to pancreatin, the synthetic equivalent of natural bird droppings. Appearance measurements, as well as optical microscope images obviously indicated that the additive improved the clearcoats resistance against pancreatin. Results revealed that surface free energy of the films was reduced in the presence of additive. It was also found that at high concentrations of additive, a significant part of it remained in the bulk, forming a second phase. This resulted in a lack of sufficient reactive groups and lead to an under-cure state at the clearcoat surface.