Investigations of spherulitic growth in industrial crystallization

The discrimination between crystal growth and aggregation is of crucial importance for the control of morphology and particle size in crystallization processes, as they are influenced in very different ways by the industrial processing environment. A collection of resembling solution-grown polycrystalline particles that differ widely in chemical nature, like elemental nickel, calcium and sodium carbonate, l-glutamic acid and an aromatic amine have been identified to grow by a spherulitic growth mechanism usually only associated with the crystallization of polymers or melts. The particles are not growing by agglomeration of small individual crystals, as often claimed in the literature. The effect of initial supersaturation, temperature and solvent composition on the spherulitic growth of calcium carbonate (vaterite) has been used to demonstrate how spherulites can grow from solution both by central multidirectional growth (in water) and by unidirectional growth followed by low angle branching (in 90 wt% ethylene glycol). The progression of non-crystallographic branching could be monitored as a function of time at intermediate initial supersaturation values, supplying direct visual evidence for spherulitic growth in this system. A reduction in initial supersaturation and temperature resulted in insufficient branching and dumbbell particles, whereas increased levels of supersaturation rapidly produced fully grown spherulites.     

Graphene Nanocomposites Prepared From Blends of Polymer Latex with Chemically Reduced Graphite Oxide Dispersions

Graphene nanocomposites are prepared by chemical reduction of graphite oxide (GO) dispersion with vitamin C in the presence of SAN latex followed by melt compounding. In this process, GO is well dispersed in an aqueous SAN emulsion before reduction. During reduction the SAN latex is adsorbed on the graphene sheets of the chemically reduced GO (CRGO). After melt compounding of such hybrid particles with SAN, the nanocomposites show uniform dispersion of CRGO in SAN resulting in improved stiffness with respect to SAN/graphite. The reduction of GO in the presence of polymer latex represents a versatile route to graphene masterbatches and does not require either drying of GO or thermal GO expansion at high temperatures.

     

Altered DNA Methylation Profiles in SF3B1 Mutated CLL Patients

Mutations in splicing factor genes have a severe impact on the survival of cancer patients. Splicing factor 3b subunit 1 (SF3B1) is one of the most frequently mutated genes in chronic lymphocytic leukemia (CLL); patients carrying these mutations have a poor prognosis. Since the splicing machinery and the epigenome are closely interconnected, we investigated whether these alterations may affect the epigenomes of CLL patients. While an overall hypomethylation during CLL carcinogenesis has been observed, the interplay between the epigenetic stage of the originating B cells and SF3B1 mutations, and the subsequent effect of the mutations on methylation alterations in CLL, have not been investigated. We profiled the genome-wide DNA methylation patterns of 27 CLL patients with and without SF3B1 mutations and identified local decreases in methylation levels in SF3B1^mut CLL patients at 67 genomic regions, mostly in proximity to telomeric regions. These differentially methylated regions (DMRs) were enriched in gene bodies of cancer-related signaling genes, e.g., NOTCH1, HTRA3, and BCL9L. In our study, SF3B1 mutations exclusively emerged in two out of three epigenetic stages of the originating B cells. However, not all the DMRs could be associated with the methylation programming of B cells during development, suggesting that mutations in SF3B1 cause additional epigenetic aberrations during carcinogenesis.     

Electronic-level interactions of tungsten oxide with unsupported Se/Ru electrocatalytic nanoparticles

Se/Ru nanoparticles - a potent non-platinum catalyst towards oxygen reduction reaction - were modified by hydrated WO₃ and investigated using the rotating disk/ring electrode methods and by synchrotron X-ray photoelectron spectroscopy. The modification resulted in an enhanced catalytic activity towards oxygen reduction reaction (ORR). Our data indicate that the oxygen reduction current starts ca. 70 mV more positive and formation of undesirable hydrogen peroxide has significantly decreased following the modification of Se/Ru with WO₃. X-ray photoelectron spectroscopy reveals that WO₃ interacts electronically with Se/Ru as the W 4f and Se 3d line-shapes change. We therefore conclude that the electronic interactions between Se/Ru and WO₃ are primarily responsible for the increase in activity and selectivity of the WO₃-modified Se/Ru towards ORR.     

Time‐ and Temperature‐Dependent Fracture Mechanics of Polymers: General Aspects at Monotonic Quasi‐Static and Impact Loading Conditions

Well‐defined correlations exist between the maxima in mechanical loss factor and the local maxima in temperature‐ or loading‐speed‐dependent fracture toughness. The non‐linear viscoelastic fracture processes and small‐strain deformations are characterised by the same Arrhenius‐type activation enthalpies. The local increase in toughness is linearly correlated with the relaxation strength of molecular relaxation processes. Stable crack propagation can be understood as a three‐phase process resulting in steady‐state stable crack growth. The normalised steady‐state crack‐tip‐opening displacement is independent of matrix material, temperature and loading speed.

     

Synthesis and processability into textile structures of radiopaque,biodegradable polyesters and poly(ester‐urethanes)

Radiopaque biodegradable polymers have been synthesized by ring‐opening polymerization of l /dl ‐lactide and caprolactone with the iodine‐containing starter molecule 2,2‐bis(hydroxymethyl)propane‐1,3‐diyl bis(2,3,5‐triiodobenzoate) followed by chain elongation with a diacid chloride or diisocyanates. The resulting polyesters and poly(ester‐urethanes) exhibited a radiopacity of 60?124% relative to an aluminium sample of the same thickness. The polymers were processed into monofilament fibres by melt‐spinning and into fibre meshes by electrospinning. All polymers were biodegradable in simulated body fluid medium under in vitro conditions and showed an excellent in vitro cytocompatibility even after several months of hydrolytic degradation. A current drawback is the relatively low tensile strength of the polymer monofilaments, which needs to be improved for applications as textile structures. Nevertheless, the new radiopaque and biodegradable polymers are promising candidates in fields of application where radiopacity of implants is an important parameter.     

Analysis of oxylipins by high-performance liquid chromatography with evaporative light-scattering detection and particle beam-mass spectrometry

The metabolism of 13 S-hydroperoxy-9Z,11E,15Z-octadecatrienoic acid was investigated in a crude enzyme extract from mung bean seedlings (Phaseolus radiatus L.). Hydroperoxide-metabolizing activity was mainly due to a hydroperoxide lyase and, to a lesser extent, to an allene oxide synthase and a peroxygenase. Oxylipins originating from hydrolysis and cyclization of the allene oxide synthase product 12,13-epoxy-9Z,11,15Z-octadecatrienoic acid and from peroxygenase catalysis were identified by high-performance liquid chromatography (HPLC) particle beam-mass spectrometry (PB-MS) and quantified by normal-phase HPLC with an evaporative light-scattering detector (ELSD). An advantage of this methodology was the possibility to avoid extensive derivatization procedures commonly used for the gas chromatographic analysis of oxylipins. Owing to a comparable sample inlet system, the ELSD served an important analytical pilot function for the PB-MS: Qualitatively identical chromatographic patterns were obtained with both detection systems. The HPLC system enabled the separation of methyl 12-oxo-phytodienoate, methyl 11-hydroxy-12-oxo-9Z,15Z-octadecadienoate, methyl 12-oxo-13-hydroxy-9Z,15Z-octadecadienoate, methyl 9-hydroxy-12-oxo-10E,15Z-octadecadienoate, methyl 13-hydroxy-9Z,11E,15Z-octadecatrienoate, methyl 15,16-epoxy-13-hydroxy-9Z,11E,15Z-octadecatrienoate, and methyl 13-hydroperoxy-9Z,11E,15Z-octadecatrienoate on a Lichrospher DIOL column within 33 min. Compared with a diode array detector, the ELSD proved to be more sensitive, in the case of methyl 12-oxo-13-hydroxy-9Z, 15Z-octadecadienoate by a factor of about 15. In addition, volatile metabolites were analyzed by capillary gas chromatography. The yield of the hydroperoxide lyase product 2E-hexenal was 49%, whereas the sum of oxylipins reached about 15%.