Molar mass of poly (ethylene terephthalate) (PET) during ultimate uniaxial drawing

The changes of the average molar mass M_w, M_n, M_z, and molar mass distributions during multistep uniaxial drawing of poly(ethylene terephthalate) (PET) to achieve ultimate mechanical properties have been studied in detail by means of size exclusion chromatography (SEC) with triple detection: concentration, viscosimetry, and light scattering, using HFIP as solvent. An increase in molar mass of PET due to post‐polycondensation and/or transesterfication during drawing at a high temperature of 160 to 230°C was found. Moreover, drawing leads to crystallization and large orientation in the amorphous phase, which results in lower molecular mobility and prevents a further growth in chain length. Crazing under extreme drawing conditions occurs and affects a decrease in molar mass.     

Manufacturing of electrical discharge machinable ZTA-TiC - hot pressing vs. spark plasma sintering

Hot pressing and spark plasma sintering were applied to manufacture electrical discharge machinable ZTA-TiC ceramics containing 17?vol.% zirconia (1.5Y) and 24?vol.% titanium carbide in an alumina matrix. Sintering was carried out at 1450–1600?°C and 40?MPa pressure with 2?h dwell for HP and 10?min for SPS. The influence of sintering conditions on mechanical properties, microstructure, phase composition and electrical conductivity was investigated. Both sintering technologies lead to fully densified samples with similar strength and toughness. Hardness was generally lower for SPS. SPS samples develop a finer microstructure. HP samples the TiC grains tend to merge at high sintering so that HP materials reach significantly higher conductivities. Productivity and energy consumption per piece can be significantly decreased by shifting to SPS. Both types of material were ED-machinable. Hot pressed ceramics showed better cutting performance and improved surface quality in trimming operations.     

A GC-based method for high-throughput screening of enantioselective catalysts

By combining two gas chromatography instruments (each containing a column with a chiral stationary phase) with the proper robotics and software, it is possible to construct an instrumental configuration which makes possible high-throughput screening of the enantioselectivity of a given catalytic reaction. As an example, the acylation-based catalytic kinetic resolution of racemic 2-phenyl-1-propanol catalyzed by mutant lipases can be about assayed, 700 exact E- and ee-determinations being possible per day. The method is, therefore, of interest in the directed evolution of enantioselective enzymes and/or in the combinatorial search for asymmetric transition metal catalysts.     

Study of PVC degradation using a fast computer scanning procedure

A computer scanning procedure for the determination of total double‐bond concentration resulting from PVC degradation is described. It is fast, fully automated, and has a very high sensitivity (5 ppm of degraded monomer units). This high sensitivity makes possible the monitoring of discoloration on a very small surface and generates very large amounts of experimental data allowing corrections for inhomogeneities and surface irregularities. The measured extinctions (E_rgb) correlate with the concentrations of double bonds and allow the estimation of degradation rates. The measuring of stabilization times and the reaction rates of stabilizers with allylic chlorides and HCI offers the capability to optimize the PVC stabilization.     

Quantitative Isotopomer Rates in Real-Time Metabolism of Cells Determined by NMR Methods

Tracer-based metabolism is becoming increasingly important for studying metabolic mechanisms in cells. NMR spectroscopy offers several approaches to measure label incorporation in metabolites, including ¹³C- and ¹H-detected spectra. The latter are generally more sensitive, but quantification depends on the proton–carbon ¹J_CH coupling constant, which varies significantly between different metabolites. It is therefore not possible to have one experiment optimised for all metabolites, and quantification of ¹H-edited spectra such as HSQCs requires precise knowledge of coupling constants. Increasing interest in tracer-based and metabolic flux analysis requires robust analyses with reasonably small acquisition times. Herein, we compare ¹³C-filtered and ¹³C-edited methods for quantification and show the applicability of the methods for real-time NMR spectroscopy of cancer-cell metabolism, in which label incorporations are subject to constant flux. We find an approach using a double filter to be most suitable and sufficiently robust to reliably obtain ¹³C incorporations from difference spectra. This is demonstrated for JJN3 multiple myeloma cells processing glucose over 24 h. The proposed method is equally well suited for calculating the level of label incorporation in labelled cell extracts in the context of metabolic flux analysis.     

The thermal springs of Bockfjorden, Svalbard: II: selected aspects of trace element hydrochemistry

Waters from the Trollkjeldene (Troll springs) and Jotunkjeldene (Jotun springs) thermal springs on northern Svalbard have been analysed by ICP-AES, ICP-MS and IC techniques for a wide range of major and trace elements. Although it is plausible that the thermal waters originate from a deep reservoir in siliceous rocks, it appears that a significant component of their hydrochemical signature is derived from dissolution of higher-level Hecla Hoek marbles. Rare earth elements (REEs) show some degree of enrichment of heavy REEs in the water phase, relative to the marbles and to the travertines that precipitate from the waters. A strong positive Eu anomaly is also observed in the waters, suggesting preferential mobilisation of Eu under reducing conditions. The ratio Nb/Ta is rather well-preserved between the marbles, the waters and the travertines.     

Rapid Estimation of NO Oxidation Kinetic Data from Experiments

Parameter estimation for Langmuir‐Hinshelwood/Hougen‐Watson type of kinetics in the field of automotive exhaust gas aftertreatment can be challenging as a great variety of parameter sets can result in a similar model quality as rate and inhibition parameters can interact during numerical optimization although they can be regarded independent from theory. This contribution introduces a method that enables the model‐based rapid estimation of NO oxidation kinetic information on a Pt‐only monolith catalyst from a straightforward set of synthesis gas test‐bench experiments.     

Fracture toughness testing of biomedical ceramic-based materials using beams,plates and discs

The testing of fracture toughness becomes problematic when only limited amount of material is available that hinders the production of typical beam specimens to be tested in bending. Here we explore fracture toughness testing methodologies that allow for small discs and plates having surface cracks to be tested in biaxial flexure using the Ball-on-3-balls (B3B) set-up, or sawed notches as in the Compact Tension geometry. The B3B-K_Ic test has shown to be versatile and account for a very small overestimation of the K_Ic-value in the order of 0.8–1.25% due to in-plane crack mispositioning, and a maximum of 4% if a worst-case scenario of additional out-of-plane mispositioning is assumed. The geometrical factor in the standard SCF method, derived by Newman and Raju, resulted in an overestimation of ～8% of the K_Ic-value compared to the new calculation by Strobl et al. for materials with Poisson’s ratio <0.3.     

Spark plasma sintering and hot pressing of ZTA-NbC materials – A comparison of mechanical and electrical properties

Zirconia toughened alumina can be made electrically conductive and thus electric discharge machinable by addition of a percolating dispersion of niobium carbide. In order to boost the productivity of the sintering process spark plasma sintering was tested at identical temperature and pressure but shorter dwell than in hot pressing. SPS sintering parameters for ZTA-NbC are developed and spark plasma sintered ceramics are compared to the hot pressed benchmark.During SPS a percolating NbC backbone of niobium carbide grains is formed which enhances electrical conductivity but impedes densification. Identical strength at however higher sintering temperature is achieved by SPS but the fracture resistance and hardness were always superior in hot pressed samples. The monoclinic content of zirconia grains in as fired SPS samples is higher despite smaller average grain size and the transformation toughening effect is less pronounced. SPS promises economic benefits due to shorter dwell and cooling cycles.