Anisotropy of cell wall polymers in branches of hardwood and softwood: a polarized FTIR study

The mechanical and physical properties of wood fibres are dependent on the organisation of their constituent polymers (cellulose, hemicellulose and lignin). Fourier Transform Infrared (FTIR) microscopy was used to examine the anisotropy of the main wood polymers in isolated cell wall fragments from branches of maple and Serbian spruce. Polarised FTIR measurements indicated an anisotropy, i.e. orientation of the cellulose microfibrils that was more or less parallel to the longitudinal axis of the cell wall. The hemicelluloses, glucomannan and xylan appeared to have a close link to the orientation of the cellulose and, thus, an orientation more parallel to the axis of the cell wall. An important result is that, in both maple and spruce samples, lignin was found to be organised in a parallel way in relation to the longitudinal cell wall axis, as well as to the cellulose. The results show that, despite the different lignin precursors and the different types of hemicelluloses in these two kinds of wood, lignin has a similar orientation, when it comes to the longitudinal axis of the cell wall.     

Phase behavior and rheological properties of DNA-cationic polysaccharide mixtures

Associative aqueous mixtures over a range of concentrations of double- (ds) or single- (ss) stranded DNA with dilute or semidilute solutions of two cationic derivatives of hydroxyethyl cellulose (cat-HEC and cat-HMHEC,(1) the latter carrying grafted hydrophobic groups), were studied. The phase behavior showed an interesting asymmetry: Phase separation occurred immediately when small (sub-stoichiometric) amounts of cationic polyelectrolyte were added to the DNA solution, but redissolution into a single cat-(HM)HEC/DNA/H(2)O phase occurred already with a modest charge excess of the cationic polyelectrolyte, at a charge ratio approximately independent of the overall polyelectrolyte concentration. Cat-HEC/dsDNA/H(2)O and cat-HEC/ssDNA/H(2)O systems presented a considerable difference in the extension of the phase separation region. The one-phase samples with excess cationic polyelectrolyte were studied by rheology. The presence of DNA strengthened the viscoelastic behavior of the solutions of the cationic polyelectrolytes, reflected in an increase in storage modulus and viscosity. Differences in phase behavior and rheology were observed, particularly between systems containing cat-HEC or cat-HMHEC, but also between dsDNA and ssDNA. Thus, these systems allow for the preparation of DNA formulations with widely variable rheology and water uptake.     

Moisture uptake in native cellulose – the roles of different hydrogen bonds: a dynamic FT-IR study using Deuterium exchange

This paper aims at a better understanding of the interaction between cellulose and moisture. In particular, the role of different hydrogen bonds in moisture uptake is investigated. Dynamic Fourier transform infrared spectroscopy (FT-IR) has been used in combination with deuterium exchange, which permits the labelling of cellulose domains with different accessibilities. The static spectra indicate a marked exchange of deuterium for the O2–H⋯O6 bonds, but only a limited exchange for the O3–H⋯O5 bonds. In the dynamic FT-IR spectra, deuteration gives rise to the growth of a broad band at wavenumbers around 2500 cm⁻¹. The rather unstructured appearance of the band suggests that deuteration is occurring only on the surface of the cellulose crystallites, i.e. in more or less non-load-carrying parts. This is corroborated by the lack of split peaks related to OD bonds in this band. In agreement with these observations, the split peak related to O3–H⋯O5 bonds and assigned to the load carrying cellulose structure increases during both H₂O and D₂O moisture conditioning, indicating a shift of the load transfer towards the backbone of the cellulose structure.     

Development of a pressurized liquid extraction and clean-up procedure for the determination of alpha-endosulfan, beta-endosulfan and endosulfan sulfate in aged contaminated Ethiopian soils

Pressurized liquid extraction (PLE) was investigated for the extraction of two endosulfan isomers and their metabolite from two real contaminated soil samples. PLE for 3x10min at 100 degrees C was proven to be more exhaustive than Soxhlet extraction (SOX) in one soil sample. On the other soil sample investigated the method was found to be equally exhaustive as SOX. The use of hazardous organic solvents such as n-hexane, toluene, and diethyl ether has been avoided in PLE and clean-up. Instead less toxic solvents have been used both at the extraction step (acetone/n-heptane) and clean-up step (ethyl acetate/n-heptane). A column Florisil clean-up procedure that consumes relatively low solvent volumes has been optimized and applied to purify soil extracts. The developed analytical procedure was validated by applying it to a certified reference soil material (CRM811-050). A recovery of 103% total endosulfan residue was obtained versus certified values.     

A Highly Active Ylide‐Functionalized Phosphine for Palladium‐Catalyzed Aminations of Aryl Chlorides

Ylide‐functionalized phosphine ligands (YPhos) were rationally designed to fit the requirements of Buchwald–Hartwig aminations at room temperature. This ligand class combines a strong electron‐donating ability comparable to NHC ligands with high steric demand similar to biaryl phosphines. The active Pd species are stabilized by agostic C?H???Pd rather than by Pd–arene interactions. The practical advantage of YPhos ligands arises from their easy and scalable synthesis from widely available, inexpensive starting materials. Benchmark studies showed that YPhos‐Pd complexes are superior to the best‐known phosphine ligands in room‐temperature aminations of aryl chlorides. The utility of the catalysts was demonstrated by the synthesis of various arylamines in high yields within short reaction times.     

Anaerobic treatment of animal byproducts from slaughterhouses at laboratory and pilot scale

Different mixtures of animal byproducts, other slaughterhouse waste (i.e., rumen, stomach and intestinal content), food waste, and liquid manure were codigested at mesophilic conditions (37°C) at laboratory and pilot scale. Animal byproducts, including blood, represent 70–80% of the total biogas potential from waste generated during slaughter of animals. The total biogas potential from waste generated during slaughter is about 1300 MJ/cattle and about 140 MI/pig. Fed-batch digestion of pasteurized (70°C, 1h) animal byproducts resulted in a fourfold increase in biogas yield (1.14L/g of volatile solids [VS]) compared with nonpasteurized animal bypproducts (0.31L/g of VS). Mixtures with animal byproducts representing 19–38% of the total dry matter were digested in continuous-flow stirred tank reactors at laboratory and pilot scale. Stable processes at organic loading rates (OLRs) exceeding 2.5g of VS/(L·d) and hydraulic retention times (HRTs) less than 40 d could be obtained with total ammonia nitrogen concentrations (NH₄−N+NH₃−N) in the range of 4.0–5.0 g/L. After operating one process for more than 1.5 yr at total ammonia nitrogen concentrations >4 g/L, an increase in OLR to 5 g of VS/(L·d) and a decrease in HRT to 22 d was possible without accumulation of volatile fatty acids.     

Moisture adsorption of glucomannan and xylan hemicelluloses

Wood and wood materials are highly sensitive to moisture in the environment. To a large extent this relates to the hygroscopicity of wood hemicelluloses. In order to increase our understanding of the effects of moisture sorption of the major wood hemicelluloses, glucomannan and xylan, model experiments using films of amorphous konjak glucomannan and rye arabinoxylan were conducted. Moisture-induced expansion and stiffness softening were characterized using dynamic mechanical testing. Both hemicelluloses showed a threshold around 5 % of moisture content above which swelling increased whereas the modulus decreased by more than 70 %. FTIR spectra, using H₂O and D₂O, indicated that even at high RH about 15 % of the hydroxyl groups were not accessible to hydrogen exchange by D₂O. For xylan both hydroxyl groups were found to exchange in the same manner while for the glucomannan the O(6)H group seemed to be the most accessible.