The Plug & Play Reactor: A Highly Flexible Device for Heterogeneous Reactions in Continuous Flow

The so‐called plug & play reactor is a novel reaction device with exchangeable reaction segments as well as modules for heating/cooling and mixing. Its performance is demonstrated for two model processes: the production of acetylsalicylic acid with a fixed bed of commercial ion‐exchange particles and a Suzuki‐Miyaura cross‐coupling with a solid Pd‐catalyst developed by us. The reaction progress was monitored by inline UV‐vis spectroscopy and compared with offline HPLC. The novel set‐up leads to quantitative yields and selectivity as well as to an improved practicability of the processes.     

Modifications in the bulk and the surface of unbleached lignocellulosic fibers induced by heat treatment without water removal: effects on tensile properties of unrefined kraft pulp

The effects of heating lab cooked never dried kraft pulp from pine and spruce at 5 % consistency to 80, 100 and 120 °C in a pressurized vessel were evaluated based on various fiber and sheet properties. The settings of pH and conductivity in the lab trial were chosen in accordance with operations such as oxygen delignification, alkaline extraction, washing or storage of pulp in an integrated paper mill. It was found that the tensile strength was reduced steadily with increasing temperature. Nuclear magnetic resonance spectroscopy showed that fiber crystallinity and pore size increased at high temperatures compared to the unheated reference. Crystallinity most likely affected the fiber flexibility and thus resulted in less and weaker fiber–fiber bonds. Atomic force microscopy indicated that the amount of precipitated lignin granules on the fiber surface was reduced with increasing temperature. The roughness of the fiber surface did not significantly change with temperature and hence did not negatively influence the tensile strength. It was remarkable that a so called reversed latency was observed. Instead of a decrease in fiber curl with temperature, the fiber became significantly more curled. A large portion of the losses in tensile strength was attributed to the increase in fiber curl and leaching of hemicelluloses from the fiber wall.     

Ultra-high field MRI for primate imaging using the travelling-wave concept

Object

Ultra-high field (UHF) neuroimaging is usually conducted with volume transmit (Tx) and phased array receive (Rx) coils, both tightly enclosing the object. The travelling-wave (TW) concept allows a remote excitation offering more flexible experimental setups. To investigate the feasibility of primate MRI in horizontal UHF MRI, we first compared the distribution of the electromagnetic fields in an oil phantom and then verified the concept with an in vivo experiment.

Materials and methods

In the phantom experiments an in-house circularly polarized hybrid birdcage coil and a self-developed patch antenna were used for Tx and an eight-element phased array antenna for Rx. B ₁ ⁺ fields were calculated and measured for both approaches. For in vivo experiments the Rx part was replaced with an optimized three-element phased array head coil. The SAR was calculated using field simulation.

Results

In the phantom the field distribution was homogenous in a central volume of interest of about 10 cm diameter. The TW concept showed a slightly better homogeneity. Examination of a female crab-eating macaque led to homogeneous high-contrast images with a good delineation of anatomical details.

Conclusion

The TW concept opens up a new approach for MRI of medium-sized animals in horizontal UHF scanners.     

A practical equation of state for non‐spherical and asymmetric systems for application at high pressures. Part 2: Extension to mixtures

In part I of this series the pure component PHCT‐DNSK equation of state (EOS) was presented. In this paper the EOS is extended to describe mixtures, particularly asymmetric mixtures containing one or more low molecular weight spherical compound together with one or more high molecular weight chain‐like compound. The EOS utilises theoretically correct mixing rules and is generally able to predict the correct trends quantitatively for binary mixtures, and in most cases outperform other EOSs. With the use of a small, temperature independent, interaction parameter the EOS is able to predict the phase behaviour of the investigated systems qualitatively. The EOS is able to predict the phase behaviour of a multi‐component system containing one or more light components and a range of heavy hydrocarbons with improved accuracy compared to other EOSs at reduced computational times. © 2011 Canadian Society for Chemical Engineering     

Application of a 2-step process for the biological treatment of sulfidic spent caustics

This research demonstrates the feasibility and advantages of a 2-step process for the biological treatment of sulfidic spent caustics under halo-alkaline conditions (i.e. pH 9.5; Na⁺ = 0.8 M). Experiments with synthetically prepared solutions were performed in a continuously fed system consisting of two gas-lift reactors in series operated at aerobic conditions at 35 °C. The detoxification of sulfide to thiosulfate in the first step allowed the successful biological treatment of total-S loading rates up to 33 mmol L⁻¹ day⁻¹. In the second, biological step, the remaining sulfide and thiosulfate was completely converted to sulfate by haloalkaliphilic sulfide oxidizing bacteria. Mathematical modeling of the 2-step process shows that under the prevailing conditions an optimal reactor configuration consists of 40% ‘abiotic’ and 60% ‘biological’ volume, whilst the total reactor volume is 22% smaller than for the 1-step process.     

Adaptive Herd- und Fahnencharakterisierung als Voraussetzung für einen effizienten Modellaufbau unter heterogenen Standortbedingungen

The Voigtl?nder camera production site in Braunschweig was operated until 1972. The facility??s use of chlorinated solvents for grease removal led to significant soil and groundwater contamination. The investigation and remediation methods that have been used at the site have not resulted in an acceptable level of remediation. Given the heterogeneous conditions, the site appears to be an excellent location for assessing the effectiveness of adaptive characterization strategies for investigations of contamination by chlorinated solvents. The Voigtl?nder source area no. V is being used as a demonstration site to assess the efficiency of different investigation and remediation methods under heterogeneous conditions. An iterative (adaptive) investigation process was conducted with sequential improvements based on increased site understanding. The lithologic and hydraulic features that could create potential migration pathways were identified, and the spatial extent of the contaminant body within the source area and, by means of control planes, within the plume was delineated. Related 2D and 3D images of the site model provide solid support for assessments of the relative effectiveness of various remediation alternatives.     

A Chiral Microporous Polymer Network as Asymmetric Heterogeneous Organocatalyst

Microporous polymer networks, composed of structure‐directing monomers (tectons), can exhibit high permanent surface area and porosity. By choice of suitable tectons various functionalities can be introduced into such networks. Here we introduce chiral BINOL derivatives as novel tectons to generate microporosity in polymer networks. The use of such monomers enables the formation of networks composed solely out of enantiomerically pure compounds. This porous network can be used as a heterogeneous organocatalyst in asymmetric reactions and gives higher enantioselectivty than the homogeneous reaction.     

Temperature dependence of the magnetic volume susceptibility of human breast fat tissue: an NMR study

Object  

Proton resonance frequency shift (PRFS)-based MR thermometry (MRT) is hampered by heat-induced susceptibility changes when applied in tissues containing fat, e.g., the human breast. In order to assess the impact of fat susceptibility changes on PRFS-based MRT during thermal therapy in the human breast, reliable knowledge of the temperature dependence of the magnetic volume susceptibility of fat, dχ_fat/dT, is a prerequisite. In this work we have measured dχ_fat/dT of human breast fat tissue, using a double-reference method to ensure invariance to temperature-induced changes in the proton electron screening constant.