Diagenetic transformation of dissolved organic nitrogen compounds under contrasting sedimentary redox conditions in the Black Sea

Remineralization of organic matter in reactive marine sediments releases nutrients and dissolved organic matter (DOM) into the ocean. Here we focused on the molecular-level characterization of DOM by high-resolution Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS) in sediment pore waters and bottom waters from contrasting redox regimes in the northern Black Sea with particular emphasis on nitrogen-bearing compounds to derive an improved understanding of the molecular transformations involved in nitrogen release. The number of nitrogen-bearing molecules is generally higher in pore waters than in bottom waters. This suggests intensified degradation of nitrogen-bearing precursor molecules such as proteins in anoxic sediments: No significant difference was observed between sediments deposited under oxic vs anoxic conditions (average O/C ratios of 0.55) suggesting that the different organic matter quality induced by contrasting redox conditions does not impact protein diagenesis in the subseafloor. Compounds in the pore waters were on average larger, less oxygenated, and had a higher number of unsaturations. Applying a mathematical model, we could show that the assemblages of nitrogen-bearing molecular formulas are potential products of proteinaceous material that was transformed by the following reactions: (a) hydrolysis and deamination, both reducing the molecular size and nitrogen content of the products and intermediates; (b) oxidation and hydration of the intermediates; and (c) methylation and dehydration.     

Evaluation of Antioxidative Constituents from Thyme

The non-polar fraction of thyme was examined for the occurrence of phenolic components and their antioxidative activity. In addition to carvacrol ( II ) and thymol ( III ), p -cymene-2,3-diol (I ; 2,3-dihydroxy-4-isopropyl-1-methylbenzene) was isolated for the first time from thyme. The structure of I was elucidated using ¹H nuclear magnetic resonance (NMR), ¹³C NMR, and mass spectrometry. Antioxidative activity was investigated with the Rancimat method (100°C) and the Schaal test (60°C). Compound I exhibited the strongest antioxidative activity which was greater than that of α-tocopherol and butylated hydroxyanisole. Five thyme species were analysed by means of HPLC with electrochemical detection for the concentration of compounds I – III . The highest amounts of I – III were found in Thymus vulgaris L.     

Comparative X-ray scattering,microscopical, and mechanical studies on rectangular plates injection molded from different types of isotactic polypropylene

Rectangular plates were injection molded from two grades of commercial polypropylene (PP) differing in the molar mass distribution. The mold was mechanically sealed when a desired pressure p_i,max (up to 1560 bar) was reached. Samples were taken from each plate at different distances from the gate and were investigated by applying various methods. In spatially resolved wide-angle X-ray studies, the cross section of the sample was scanned with a fine X-ray beam (collimated by a Kratky small-angle camera) and the intensity of scattering was registered by a linear detector as a function of position in the cross section. The evaluation of the scattering data delivered profiles of several parameters, describing the distribution of crystallite modification β-PP and γ-PP, the degree of orientation, the size of crystallites, and interplanar spacing, depending on the distance from surface. These results and those from measurements of birefringence and elongation at break, and from polarization microscopy and transmission electron microscopy, provided details of the layered structures in the plates, at different flow lengths, and allowed far-reaching statements about the influence of molecular properties and processing conditions on the development of texture in the plates.     

On the Origin of a Low Angle Spacing in Starch

The structure of starch granules from different botanical sources was studied by transmission electron microscopy and small-angle X-ray diffraction. Electron micrographs of negatively stained starch granule fragments show a rippled fibrous structure. The ripples are interpreted as being stacks of thin crystalline lamellae comprising the linear α-(1→4) chains of the amylopectin. Optical diffraction analysis of the electron micrographs showed that the spacing of the ripples varies from 9.2 nm in potato starch to 10.4 nm in barley starch. This correlates well with the position of a Bragg peak at appr. 10 nm measured by small-angle X-ray diffraction. These observations indicate that the Bragg peak arises from the alternating amorphous and crystalline regions seen as ripples in the electron micrographs.     

SIMULATION OF THE PROCESS STABILITY OF HPC MILLING OPERATIONS

The optimisation of high-performance cutting (HPC) processes under technological and economical aspects often proves to be extremely difficult due to the appearance of process instabilities, so-called “chatter”. The identification of ideal process parameters often involves the systematic testing with varied cutting parameters. Simulation of the process stability offers a less costly way of optimising processes prior to production. However, the predictions for the stability of high performance milling processes exhibit great deviation from experimental results. The objective is to analyse and to prevent errors within the simulation methods to make stability simulation a reliable tool in process planning. In order to improve the quality of stability simulation, the interacting Systems “Machine Tool” and “Cutting Process” are analysed individually. Methods for the coupled simulation of both systems are implemented to identify stable working conditions. As a result of this work, a time domain simulation environment for the investigation of high performance milling operations is presented. It considers the complex behaviour of the cutting process as well as the speed dependent machine tool dynamics. Cutting tests have been conducted to verify the benefit of the enhanced simulation method.     

4-Acyl-2-acylamino-4,5-dihydro-1,3,4-thiadiazole durch Acylierung von Thiosemicarbazonen

4-Acyl-2-acylamino-4,5-dihydro-1,3,4-thiadiazoles by Acylation of Thiosemicarbazones Thiosemicarbazones and acid anhydrides or halides react to 4-acyl-2-acylamino-4,5-dihydro-1,3,4-thiadiazoles ( 2a – 2v ) in high yields. 3-Acyl-2-amino-4,5-dihydro-1,3,4-thiadiazoles 5 are proved as intermediates in this conversion. In special cases they can be isolated or submitted to further acylation with an other acylating agent. ¹H-n.m.r., ¹³C-n.m.r. and mass spectroscopic data of compounds 2a – 2v and 5a – 5e are given. The preparation of the compounds 2 can also be carried out starting with a carbonyl compound and thiosemicarbazide without isolation of the thiosemicarbazone.     

ortho-Spezifische Bromierung von Phenolen

Ortho-Specific Bromination of Phenols Phenol as well as 3-substituted phenols are brominated exclusively in the orthopositions by N.N-dibromomethylamine, yielding 2.6-dibrominated phenols in excellent yields. Phenols bearing an ortho-substituent need N-bromomethylamine as the brominating agent to take up one bromine atom into the free ortho-position. para-Bromination is not observed in either case. 1-Naphthol gives 2-bromo-1-naphthol, 8-hydroxyquinoline gives 7-bromo-8-hydroxyquinoline with 80% and 98% yield respectively. ortho-Specific chlorination of phenols was carried out in some cases using N-chloro-alkylamines.