Cholesteric and photoreactive polyesters

Several classes of cholesteric and photoreactive homo- and copolyesters were synthesized and characterized. Most of these polyesters were prepared in such a way that a chiral spacer (e.g. isosorbide) was polycondensed with a photoreactive dicarboxylic acid, such as 4-carboxycinnamic acid, benzene- 1,4-bisacrylic acid, 4-(4′-carboxyphthalimido)cinnamic acid. In several cases other dicarboxylic acids, such as naphthalene-2,6-dicarboxylic acid or 4-aminobenzoic acid trimellitimide were cocondensed to favor the formation of a Grandjean texture. When ‘sugar diols’ such as isosorbide or isomannide were used as chiral building blocks, suitable diphenols were required as comonomers to stabilize the LC phase. Most polyesters were capable of forming a selectively reflecting Grandjean texture, which can be fixed by crosslinking using UV light. An alternative synthetic strategy based on chiral, substituted terephthalic acids is discussed.     

Blends of ethylene–octene copolymers with different chain architectures – Morphology,thermal and mechanical behavior

Blends of two elastomeric ethylene–octene copolymers with similar octene contents having a random (ORC) and a blocky architecture (OBC) are prepared by melt mixing. The thermal and mechanical properties of ORC, OBC and their blends are investigated by DSC, dynamic mechanical analysis and tensile tests. The morphology of the semi-crystalline samples is studied by AFM and WAXS. Two types of crystals have been observed: (i) Orthorhombic crystals forming lamellae with an estimated thickness of about 13 nm composed mainly of long polyethylene-like sequences of OBC that melt a temperature of about 120 °C and (ii) fringed micellar crystals with a thickness of 2–4 nm formed basically by short polyethylene-like sequences of ORC that have melting temperatures between 30 and 80 °C. The amorphous phase contains a relatively homogeneous mixture of segments of both components indicated by the relatively uniform shape of the loss modulus peaks from dymamic-mechanical measurements for all investigated copolymers and blends. ORC crystallization is hindered in blends as indicated by lower melting enthalpies. This might be related to the high octene content of the amorphous phase at the relevant crystallization temperature as well as geometrical constraints since ORC crystallization occurs in an already semi-crystalline polymer. The results of tensile tests show that the mechanical behavior can be tailored via blend composition and morphology of the semi-crystalline material. The findings clearly indicate that blending is a powerful strategy to optimize the properties of polyolefin-based copolymers.     

Bulk Crystallization of Proteins by Low‐Pressure Water Evaporation

An advanced technique for bulk protein crystallization based on solvent evaporation is introduced. Hen egg white lysozyme is crystallized from its buffered aqueous solution in a stirred tank at low pressure and, thus, moderate boiling temperatures. No crystallizing agent to reduce the solubility is needed for crystallization. The biological activity of the enzyme remains unchanged during the process and a high crystal yield is achieved. Tetragonal and rod‐like lysozyme crystals, presumably of orthorhombic type, are crystallized at different boiling temperatures. This crystallization technique is proposed as a promising option to crystallize proteins economically, controllably, and gently. This method may replace standard salt‐out steps in existing production processes.     

Chemical Profiles of Scent Gland Secretions in the Cyphophthalmid Opilionid Harvestmen, <Emphasis Type="Italic">Siro duricorius</Emphasis> and <Emphasis Type="Italic">S. exilis</Emphasis>

Gas chromatographic–mass spectrometric analyses of the scent gland secretions of Siro duricorius and S. exilis (Opiliones, Cyphophthalmi, Sironidae) revealed a set of 24 components, comprising a series of saturated and unsaturated methyl ketones (C11–C15) and four naphthoquinones. Whereas the scent gland secretions of S. duricorius, collected in Austria, and S. exilis from USA were qualitatively nearly indistinguishable (with the exception of acetophenone that was specific to S. duricorius), they distinctly differed in their relative quantitative compositions: major components of the secretion of S. duricorius were 7-tridecen-2-one, tridecan-2-one, undecan-2-one, 1,4-naphthoquinone, 6-methyl-1,4-naphthoquinone (tentatively identified only), and 4-chloro-1,2-naphthoquinone. In contrast, in S. exilis a compound tentatively identified as 6-methyl-4-chloro-1,2-naphthoquinone was present in large amounts (in S. duricorius a trace component), whereas undecan-2-one only occurred in minor quantities. Secretion profiles of juveniles and adults (both sexes) of each species showed high correspondence.This is the first report on the chemistry of scent gland secretions of the opilionid suborder Cyphophthalmi. 4-Chloro-1,2-naphthoquinone was identified as a new exocrine product of arthropods, whereas 1,4-naphthoquinone and the tentatively identified 6-methyl-1,4-naphthoquinone are known constituents of exocrine secretions from one species of palpatorid opilionids, Phalangium opilio. In contrast, all ketones identified were new for opilionid scent glands, although similar ketones are characteristic of scent gland secretions of palpatorid genera Leiobunum and Hadrobunus. With regard to the near-basic position of Cyphophthalmi in currently proposed phylogenetic trees of Opiliones, naphthoquinones and ketones from Siro may represent the condition ancestral to the (derived) naphthoquinone- and ketone-rich secretions in phalangid Palpatores.     

Combinatorial micro electrochemistry: Part 1. Automated micro electrosynthesis of iminoquinol ether and [1,2,4]triazolo[4,3-a]pyridinium perchlorate collections in the wells of microtiter plates

A computer-controlled instrument, based on scanning electrochemical microscope technology, is employed in the miniaturized combinatorial electrosynthesis of localized compound collections. Libraries of iminoquinol ethers and triazolo-pyridinium ions are generated in the wells of microtiter plates by potentiostatic electrolysis. Several experimental protocols are described and implemented. Progress of the electrolyses is monitored by microelectrode steady-state voltammetry and product formation is screened by HPLC/MS.     

Morphological influences on the electrical sintering process of Aerosol Jet and Ink Jet printed silver microstructures

The morphology of non-sintered printed structures depends on the applied printing process. Aerosol Jet and Ink Jet printed silver structures have been post-treated by furnace and electrical sintering. The resulting different morphologies of the structures were investigated optically by scanning electron microscopy and electrically by measuring the specific electrical resistances. Aerosol Jet printed silver required higher temperature during furnace sintering compared to Ink Jet printed structures to reach the same specific resistance. At temperatures above 200 °C an influence of the printing process on the final electrical resistance was not observed anymore. The electrical sintering with direct current of Aerosol Jet and Ink Jet printed silver microstructures showed lower specific resistances for the aerosol generated structures. Electrical sintering was extended by an electronic regulator module (ERM), which allows the sintering of the printed structures to a specified target resistance. While the average resistance of the structures is depending on accurate adjustment of the ERM, the maximum standard deviation of the resistance values is only 2 % which is much better than in conventional sintering.     

Poloxamer-based hydrogels hardening at body core temperature as carriers for cell based therapies: in vitro and in vivo analysis

Cell-based regenerative therapies for bone defects usually employ bone precursor cells seeded on solid scaffolds. Thermosensitive hydrogels that harden at body core temperature are promising alternative cell carriers as they are applicable minimally invasively. We modified Pluronic^® P123 with different chain extenders and assessed rheology and biocompatibility of the resulting hydrogels. The best candidate was tested in a rat’s femoral defect model. All gels hardened above 25 °C with butane-diisocyanate-hydrogels (BDI-gels) displaying the highest storage moduli. BDI-gels showed the most favourable biocompatibility and did not affect cellular adipogenic or osteogenic differentiation in vitro. Implantation of BDI-hydrogel into femoral defects did not impede bone healing in vivo as evidenced by μCT and histological analysis. We conclude that thermosensitive BDI-gels are promising alternative cell carriers. The gels harden upon injection in vivo without interfering with bone metabolism. Further experiments will assess the gels’ capacity to effectively transport living cells into bone defects.     

Introduction: Perspectives on Cold War Science in Small European States

With this introduction we aim to illuminate Western Europe's place on the map of Cold War science and, specifically, to draw attention to the differences in and the diversity of Western European Cold War science in comparison to the United States. By discussing narratives of Cold War science in small states and asking how they fit into the European condition, we suggest that the fact of being a small state affects the conditions for and the scope of Cold War science. As a whole, this special issue also emphasizes the importance of the spatial dimension; that is, the significant dependence of Cold War science on geographical relations and geopolitical interests.