Evaluation and simulation of the peel behavior of polyethylene/polybutene‐1 peel systems

The peel characteristics of sealed low‐density polyethylene/isotactic polybutene‐1 (PE‐LD/iPB‐1) films, with different contents of iPB‐1 up to 20 m.‐% (mass percentage), were evaluated and simulated in dependence on the iPB‐1 content, and in dependence on the peel rate. Sealing involves close contact and localized melting of two films for a few seconds. The required force, to separate the local adhered films, is the peel force, which is influenced, among others, by the content of iPB‐1. The peel force decreases exponentially with increasing iPB‐1 content. Transmission electron microscopy studies reveal a favorable dispersion of the iPB‐1 particles within the seal area, for iPB‐1 concentrations ≥6 m.‐%. Here, the iPB‐1 particles form continuous belt‐like structures, which lead to a stable and reproducible peel process. The investigation of the peel rate‐dependency on the peel characteristics is of important interest for practical applications. The peel force increases with increasing peel rate by an exponential law. A numerical simulation of the present material system proves to be useful to comprehend the peel process, and to understand the peel behavior in further detail. Peel tests of different peel samples were simulated, using a two‐dimensional finite element model, including cohesive zone elements. The established finite element model of the peel process was used to simulate the influence of the modulus of elasticity on the peel behavior. The peel force is independent of the modulus of elasticity, however, the peel initiation value increases with increasing modulus of elasticity. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Toughness optimization of glass‐fiber reinforced PA 6/PA 66‐based composites: Effect of matrix composition and colorants

Mixing of polyamide 6 (PA 6) and polyamide 66 (PA 66) is integrated in the trend of development of new and improved materials by combination of different polymers and some reinforcing materials to polymer composites. The specific polymer composite PA 6/PA 66 reinforced with short glass‐fibers combines the good coloring of PA 6, and the small moisture absorption of PA 66. Technical applications of PA 6/PA 66 composites are mainly used in the automotive industry. Specific requirements of this industry lead to the necessity to optimize the material resistance against crack propagation of the PA 6/PA 66 composites, using mechanical and fracture mechanical methods. So, the present investigations focus on fracture mechanics toughness optimization of the PA 6/PA 66 composites, including unstable and stable crack growth. The aim of this toughness optimization is to find out the optimal mixing ratio of PA 6/PA 66. Applications of PA 6/PA 66 in the automotive industry and specific client wishes are the main reasons for black‐coloring of the PA materials. The influence of several black‐colorants (carbon black, nigrosine, spinel, iron oxide) on mechanical and fracture mechanical properties of the PA composites is also investigated using fracture mechanical methods. As experimental fracture mechanical method, preferentially, the instrumented Charpy impact test (ICIT) and the new cut method to determine the stable crack growth of glass‐fiber reinforced materials was used. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Synthesis and Pharmacological In Vitro Investigations of Novel Shikonin Derivatives with a Special Focus on Cyclopropane Bearing Derivatives

Melanoma is the deadliest form of skin cancer and accounts for about three quarters of all skin cancer deaths. Especially at an advanced stage, its treatment is challenging, and survival rates are very low. In previous studies, we showed that the constituents of the roots of Onosma paniculata as well as a synthetic derivative of the most active constituent showed promising results in metastatic melanoma cell lines. In the current study, we address the question whether we can generate further derivatives with optimized activity by synthesis. Therefore, we prepared 31, mainly novel shikonin derivatives and screened them in different melanoma cell lines (WM9, WM164, and MUG-Mel2 cells) using the XTT viability assay. We identified (R)-1-(1,4-dihydro-5,8-dihydroxy-1,4-dioxonaphthalen-2-yl)-4-methylpent-3-enyl 2-cyclopropyl-2-oxoacetate as a novel derivative with even higher activity. Furthermore, pharmacological investigations including the ApoToxGlo^TM Triplex assay, LDH assay, and cell cycle measurements revealed that this compound induced apoptosis and reduced cells in the G1 phase accompanied by an increase of cells in the G2/M phase. Moreover, it showed hardly any effects on the cell membrane integrity. However, it also exhibited cytotoxicity against non-tumorigenic cells. Nevertheless, in summary, we could show that shikonin derivatives might be promising drug leads in the treatment of melanoma.     

(S)-Reutericyclin: Susceptibility Testing and In Vivo Effect on Murine Fecal Microbiome and Volatile Organic Compounds

We aimed to assess the in vitro antimicrobial activity and the in vivo effect on the murine fecal microbiome and volatile organic compound (VOC) profile of (S)-reutericyclin. The antimicrobial activity of (S)-reutericyclin was tested against Clostridium difficile, Listeria monocytogenes, Escherichia coli, Enterococcus faecium, Staphylococcus aureus, Staphylococcus (S.) epidermidis, Streptococcus agalactiae, Pseudomonas aeruginosa and Propionibacterium acnes. Reutericyclin or water were gavage fed to male BALBc mice for 7 weeks. Thereafter stool samples underwent 16S based microbiome analysis and VOC analysis by gas chromatography mass spectrometry (GC-MS). (S)-reutericyclin inhibited growth of S. epidermidis only. Oral (S)-reutericyclin treatment caused a trend towards reduced alpha diversity. Beta diversity was significantly influenced by reutericyclin. Linear discriminant analysis Effect Size (LEfSe) analysis showed an increase of Streptococcus and Muribaculum as well as a decrease of butyrate producing Ruminoclostridium, Roseburia and Eubacterium in the reutericyclin group. VOC analysis revealed significant increases of pentane and heptane and decreases of 2,3-butanedione and 2-heptanone in reutericyclin animals. The antimicrobial activity of (S)-reutericyclin differs from reports of (R)-reutericyclin with inhibitory effects on a multitude of Gram-positive bacteria reported in the literature. In vivo (S)-reutericyclin treatment led to a microbiome shift towards dysbiosis and distinct alterations of the fecal VOC profile.     

Multiparameter microscopy and spectroscopy for single-molecule analytics

The ability to monitor several parameters simultaneously from distinct individual fluorescent reporter molecules facilitates the disentanglement of complex and interacting systems and opens new perspectives in areas from basic science to biopharmaceutical technology. By combining annular illumination microscopy, time-correlated single-photon counting, and multichannel detection, we were able to determine 14 independent parameters from one individual fluorophore. The whole set of parameters was deduced from the few properties of the fluorescence photons, i.e., arrival time, wavelength, and polarization. With this approach, the intensity, the polarization, and the spectral dynamics can be analyzed on a nanosecond time scale and the mean values can be monitored with submillisecond time resolution. Nanosecond spectral dynamics of single molecules has been observed, to the best of our knowledge, for the first time. From our experience, we can determine all parameters for more than 30% of the illuminated fluorophores in biological samples and for more than 80% in doped polymeric films.     

Natural versus wastewater derived dissolved organic carbon: implications for the environmental fate of organic micropollutants

The interaction of organic micropollutants with dissolved organic carbon (DOC) can influence their transport, degradation and bioavailability. While this has been well established for natural organic carbon, very little is known regarding the influence of DOC on the fate of micropollutants during wastewater treatment and water recycling. Dissolved organic carbon-water partition coefficients (K_DOC) for wastewater derived and reference DOC were measured for a range of micropollutants using a depletion method with polydimethylsiloxane disks. For micropollutants with an octanol-water partition coefficient (log K_OW) greater than 4 there was a significant difference in K_DOC between reference and wastewater derived DOC, with partitioning to wastewater derived DOC over 1000 times lower for the most hydrophobic micropollutants. The interaction of nonylphenol with wastewater derived DOC from different stages of a wastewater and advanced water treatment train was studied, but little difference in K_DOC was observed. Organic carbon characterisation revealed that reference and wastewater derived DOC had very different properties due to their different origins. Consequently, the reduced sorption capacity of wastewater derived DOC may be related to their microbial origin which led to reduced aromaticity and lower molecular weight. This study suggests that for hydrophobic micropollutants (log K_OW > 4) a higher concentration of freely dissolved and thus bioavailable micropollutants is expected in the presence of wastewater derived DOC than predicted using K_DOC values quantified using reference DOC. The implication is that naturally derived DOC may not be an appropriate surrogate for wastewater derived DOC as a matrix for assessing the fate of micropollutants in engineered systems.     

Rationalisierung des Zeichnungswesens im Chemie-Apparatebau

Rationalizing drawings for chemical apparatus . For small and medium-sized manufacturers of apparatus, producing drawings may constitute a disproportionate waste of time and personnel, particularly when no new designs are involved but only modification or improvement of drawings supplied by the customer. One possibility for rationalizing drawing is to simplify the old-fashioned approach by using symbols for frequently drawn or standard items, or by listing alphanumerically. This presumes a kind of systematization permitting determination of those symbols and their reasonable use, as well facilitating rationalization by means of data processing. There are different approaches to computer-aided drawing (from computer controlled drawing-board to interactive screens); here a CAD programme is presented which was especially developed for graphic presentation of chemical apparatus, and which can be used without learning a programming language.     

A method for determination of length distributions of multiwalled carbon nanotubes before and after melt processing

A relatively simple method to determine the length distribution of carbon nanotubes (CNTs) before and after melt processing was developed. This involves the selection of a suitable solvent for dispersing pristine CNTs as well as to dissolve the matrix of melt mixed composites and the choice of an appropriate nanotube concentration. The length of suitably individualized CNTs was visualized using transmission electron microscopy and length distributions were measured using image analysis. Examples are shown for Baytubes® C150HP and Nanocyl™ NC7000 and their melt mixed composites with polycarbonate where the same procedure was applied to both, measuring the initial length distribution and the distribution after recovering from the composites. These results indicated a significant shortening after melt processing up to 30% of the initial length.