Frequency-domain method based on the singular value decomposition for frequency-selective NMR spectroscopy

In several applications of NMR spectroscopy the user is interested only in the components lying in a small frequency band of the spectrum. A frequency selective analysis deals precisely with this kind of NMR spectroscopy: parameter estimation of only those spectroscopic components that lie in a preselected frequency band of the NMR data spectrum, with as little interference as possible from the out-of-band components and in a computationally efficient way. In this paper we introduce a frequency-domain singular value decomposition (SVD)-based method for frequency selective spectroscopy that is computationally simple, statistically accurate, and which has a firm theoretical basis. To illustrate the good performance of the proposed method we present a number of numerical examples for both simulated and in vitro NMR data.     

Fe2O3–Al2O3 oxygen carrier materials for chemical looping combustion,a redox thermodynamic and thermogravimetric evaluation in the presence of H2S

Journal of Thermal Analysis and Calorimetry - Alumina-supported Fe2O3 oxygen carrier material (OCM) system is among the most promising OCM systems for solid and gaseous fuel CLC. This work utilizes...     

A practical synthesis of (all-Z)-eicosa-3,6,9,12-tetraene, a pheromone component isolated from emerald moths

A short and practical synthesis of (all-Z)-eicosa-3,6,9,12-tetraene, a component of the emerald moth pheromone is reported. Two different methodologies are used both starting with the natural polyunsaturated fatty acid (all-Z)-eicosa-5,8,11,14,17-pentaenoic acid (EPA). The methodology can be used for the syntheses of a homologous series of analogues of the pheromone that may be practical for analytical purposes of similar natural products.     

Lex M versus MCS-M

We study the problem of minimal triangulation of graphs. One of the first algorithms to solve this problem was Lex M, which was presented in 1976. A new algorithm, and a simplification of Lex M called MCS-M, was presented in 2002. In this paper we compare these two algorithms and show that they produce the same set of triangulations, answering an open question mentioned by the authors of MCS-M.     

Efficient separation of oxidized cello-oligosaccharides generated by cellulose degrading lytic polysaccharide monooxygenases

We present an evaluation of HPLC-based analytical tools for the simultaneous analysis of native and oxidized cello-oligosaccharides, which are products of enzymatic cellulose degradation. Whereas cello-oligosaccharides arise from cellulose depolymerization by glycoside hydrolases, oxidized cello-oligosaccharides are produced by cellobiose dehydrogenase and the recently identified copper dependent lytic polysaccharide monooxygenases (LPMOs) currently classified as CBM33 and GH61. The latter enzymes are wide-spread and expected to play crucial roles in further development of efficient enzyme technology for biomass conversion. Three HPLC approaches with well documented performance in the field of oligosaccharide analysis have been investigated: high-performance anion-exchange chromatography (HPAEC), hydrophilic interaction chromatography (HILIC) and porous graphitized carbon liquid chromatography (PGC-LC). HPAEC with pulsed amperometric detection (PAD) was superior for analysis of oxidized oligosaccharides, combining the best separation with superior sensitivity for oligosaccharide species with a degree of polymerization (DP) ranging from 1 to 10. Furthermore, the HPAEC method can be optimized for operation in a high-throughput manner (run time 10 min). Both PGC-LC and HILIC allow reasonable run times (41 and 25 min, respectively), with acceptable separation, but suffer from poor sensitivity compared to HPAEC-PAD. On the other hand, PGC-LC and HILIC benefit from being fully compatible with online mass spectrometry. Using an LC–MS setup, these methods will deliver much better sensitivity than what can be obtained with conventional detectors such as ultraviolet-, charged aerosol-, or evaporative light scattering and may reach sensitivities similar to or even better than what is obtained in HPAEC-PAD. Pure oxidized cello-oligosaccharide standards, ranging from DP2 to DP5, were obtained by semi-preparative PGC and characterized by MS and NMR analysis.