Physico‐optical properties of a crosslinked hyaluronic acid scaffold for biomedical applications

Optical techniques are increasingly employed for monitoring cell–matrix interactions in suitably prepared 3D scaffolds. The ability of designing and realizing synthetic extracellular matrix with well‐controlled optical properties is a crucial need in this field. For this purpose, a crosslinked hyaluronic acid (HA) scaffold is prepared. Fourier transform infrared and ultraviolet–visible spectroscopies enable to monitor the scaffold preparation process and to evidence scaffold high transparency and low fluorescence in the visible range. 3D optical characteristics of the HA scaffold are tested by two‐photon microscopy (TPM) imaging of embedded fluorescent microbeads and alive keratinocytes labeled with vital PKH67 dye at different depths from the scaffold surface. Some useful indications about the potentiality of TPM measurements for the determination of attenuation coefficient of turbid media are also reported. Moreover, the use of the presented HA scaffold for preparing tissue phantoms for fluorescence imaging or diffuse imaging is proposed. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45243.     

A study on antioxidant depletion and degradation in polyolefin‐based geosynthetics: Sacrificial versus regenerative stabilization

Plastic products used in geotechnical engineering, so‐called geosynthetics, are often made of polyolefins (polyethylene or polypropylene) and stabilized against oxidative degradation by antioxidants (AO). Three types of AO “packages” are used: (P1) phenols and phosphites/sulfides, (P2) hindered amines (HAS) with a marginal stabilization P1 of the basic resin, and (P3) a combination of packages P1 and P2 with comparable amounts of phenol and HAS. We report about long‐lasting oven aging and water immersion tests at 80°C of 29 different polyolefin‐based products (geomembranes, geonets, and geotextiles). Pronounced differences in the degradation behavior were found depending solely on the type of AO package. In case of P1, the oxidative degradation is prevented by the AO. Autocatalytic oxidation only begins after depletion of AO and may lead to catastrophic failure depending on the environmental conditions. In case of P2, degradation starts right from the beginning. However, it is decelerated and proceeds gradually. In case of P3, the degradation behavior seems to be a superposition of the characteristics obtained for P1 and P2. Plotting the fractional loss of the AO in P1 and P2 as function of the square root of aging time, we identified two regimes of AO depletion. We suggest attributing this observation to the different mechanisms of AO depletion. POLYM. ENG. SCI., 56:129–142, 2016. © 2015 Society of Plastics Engineers     

Information structure in African languages: corpora and tools

In this paper, we describe tools and resources for the study of African languages developed at the Collaborative Research Centre 632 “Information Structure”. These include deeply annotated data collections of 25 sub-Saharan languages that are described together with their annotation scheme, as well as the corpus tool ANNIS, which provides unified access to a broad variety of annotations created with a range of different tools. With the application of ANNIS to several African data collections, we illustrate its suitability for the purpose of language documentation, distributed access, and the creation of data archives.     

Organochlorine residues in the edible part of eels of different origins

Fifty-four eel samples from 11 different countries were analysed by capillary gas chromatography for levels of the pesticides aldrin, endrin, hexachlorobenzene,- and-BHC, lindane, heptachlor, octachlorostyrene, pp-DDT, pp-DDD, pp-DDE, and for the levels of the PCB congeners 28, 52, 101, 138, 153, and 180. Wild eels, especially from the Baltic Sea area, had elevated contents compared to farmed eels. The mean contamination level reached only 1–5% of the allowable values given by German directives and never exceeded the official limits.

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Chlororganische Rückstände im eßbaren Anteil von Aalen verschiedener Herkunft

Zusammenfassung In 54 geräucherten und unbehandelten Aalproben aus 11 Ländern wurden die Gehalte der chlororganischen Pesticide Aldrin, Endrin, Hexachlorbenzol;-,-HCH, Lindan, Heptachlor, Octachlorstyrol, pp-DDT, pp-DDD, pp-DDE, sowie die Gehalte der PCB-Kongenere 28, 52, 101, 138, 153 und 180 gaschromatographisch ermittelt. Wildaale, insbesondere aus den Ostsee-Anrainerstaaten, zeigten im Vergleich zu Zuchtaalen leicht erhöhte Werte. Alle Gehalte lagen jedoch weit unter den gesetzlich festgelegten Grenzwerten. Im Mittel wurden die erlaubten Höchstmengen nur zu 1–5% ausgeschöpft.

     

Solubility of nitrogen in austenitic FeCrMn alloys

The equilibrium solubility of nitrogen in austenitic iron-chromium, iron-manganese, and iron-chromium-manganese alloys with mass up to 20 % Cr and 18 % Mn was measured in the temperature range 1273 to 1473 K. The following interaction parameters were obtained: (1) Describing the effect of chromium and/or manganese on the nitrogen solubility by the excess term , the present measurements correspond satisfactorily to those of Hertzmann and Jarl and of Zheng in the system Fe-Cr-N, but they differ somewhat from values calculated by means of parameters published by Frisk. For the system Fe-Mn-N the present measurements correspond to measurements by Grabke et al. and to values calculated with parameters published by Qiu. Using parameters deduced from the present measurements in the austenitic Fe-Cr-Mn-N system similar nitrogen solubilities were calculated as Zheng had measured, but small deviations were found between the analysis by Qiu and this investigation.     

Design and synthesis of cyclopeptide analogues of the potent histone deacetylase inhibitor FR235222

Various structurally modified analogues of FR235222 (1), a natural tetrapeptide inhibitor of mammalian histone deacetylases, were prepared in a convergent approach. The design of the compounds was aimed to investigate the effect of structural modifications of the tetrapeptide core involved in enzyme binding in order to overcome some synthetic difficulties connected with the natural product 1. The modifications introduced could also help identify key structural features involved in the mechanism of action of these compounds. The prepared molecules were subjected to in vitro pharmacological tests, and their potency was tested on cultured cells. Two of the components of the array were found to be more potent than the parent compound 1 and almost as efficient as trichostatin A (TSA). These results demonstrate that it is possible to synthesize highly active cyclic tetrapeptides using commercially available amino acids (with the exception of 2-amino-8-oxodecanoic acid, Ahoda). The nature of the residue in the second position of the cyclic peptide and the stereochemistry of the Ahoda tail are important for the inhibitory activity of this class of cyclic tetrapeptide analogues.     

Single-pulse fiber Bragg gratings and specific coatings for use at elevated temperatures

The technique of recording fiber Bragg gratings (FBGs) with single exposure pulses during the fiber drawing process allows production of such gratings in complex array structures, with high mechanical strength of the fiber and in a simple and cost-efficient way. This is of special interest for the growing field of fiber sensor applications with FBGs. A general advantage of fiber sensor systems is their ability to be used also at elevated temperatures compared with conventional electric or electronic sensors. For this purpose, the fiber itself as well as the grating structure and the fiber coating should be stable under such elevated temperature conditions. We have investigated different coating materials and possibilities of making temperature-stable FBGs of types I and II in the range of 100 degrees C-1000 degrees C with good reflection efficiency by single-pulse exposure during the fiber drawing process.     

Triphenyltin (IV) derivatives of N-acetyl amino acids,N-acetyl dipeptides and tripeptides: Preparation,NMR investigations and NMR spectroscopic resolution of the enantiomeric composition

Triphenyltin(IV) derivatives of N-acetyl amino acids ( 1a–g ) and N-acetyl di- ( 2a–f ) or tripeptides ( 3 ) mostly in the (L )- and the racemic (DL )-form have been prepared from bis(triphenyltin)oxide and the appropriate N-acetyl amino acid or N-acetyl peptide using various dehydrating agents. The compounds were characterized by NMR spectroscopy and elemental analysis. These compounds were studied at different concentrations and temperatures, revealing a strong self-association tendency. NMR investigations were undertaken in order to highlight preferred conformations of the peptide derivatives due to possible strong intramolecular associations between tin and nucleophilic donor atoms of the peptide moiety in weakly polar solvents. No preferred conformation was found which was in accordance with the underivatized peptides. The enantiomeric composition was determined by means of ¹H NMR spectroscopy using (−)-quinine hydrochloride and S-(−)-1-phenylethylamine as chiral solvating agents.