Newtonian Viscosity of Amorphous Silicon Carbonitride at High Temperature

The creep viscosity of chemical-precursor-derived silicon carbonitride (SiCN), which is known to remain predominantly amorphous at temperatures below 1400°C, was measured in the temperature range 1090-1280°C. Experiments were done in uniaxial compression at constant loads in pure nitrogen atmosphere. The creep behavior exhibited three stages. In stage I the strain rate decreased rapidly with time and deformation was accompanied by densification. In stage II the samples exhibited a steady-state creep rate. In stage III, which commenced after long-term deformation, creep gradually declined to rates that were below the sensitivity of our apparatus. The relative density of the specimens during stage II and stage III remained constant at ≅2.3 g/cm³. The shear viscosity in stage II was nearly Newtonian and was measured to be 1.3 × 10¹³-5.0 10¹³ Pa·s at 1280°C, which is approximately 10³ times the value for fused silica. The creep-hardened as well as uncrept specimens contained silicon nitride crystallites. The volume fraction of these crystals was variable but always less than 5%. Such a small volume fraction of crystals does not explain the dramatic creep-hardening behavior in stage III, even if it is assumed that the crystals formed during creep deformation in stage II.     

Analyzing Thermal Conductivity of Polyethylene‐Based Compounds Filled with Copper

The thermal conductivity (TC) of different polymeric materials is measured via four commercially available testing devices: TPS2500S by Hot Disk (Hot Disk), Transient Hot Bridge (THB) by Linseis, the Laser Flash Analysis (LFA) by NETZSCH, and the DTC‐300 by TA Instruments. The investigated materials include high‐density polyethylene (HDPE) and linear low‐density polyethylene (LLDPE) which are analyzed as received and after being compounded with copper particles. The filler geometry and ratio are varied systematically. Major differences in the TC generated by the different measurement methods are revealed and analyzed in detail. Moreover, material‐induced impacts on the TC as well as technology‐induced impacts on the TC are outlined comprehensively.     

Effect of medium composition on biohydrogen production by the extreme thermophilic bacterium Caldicellulosiruptor saccharolyticus

Up to now, the analysis of the effects of medium composition on biohydrogen production of Caldicellulosiruptor saccharolyticus was focused mainly on salt concentrations and complex compounds. Within this work we studied the effects of the presence of organic and/or inorganic nitrogen in the medium composition aiming to induce metabolic changes in C. saccharolyticus   to improve its hydrogen evolution rate (HER) and hydrogen specific productivity (qH₂)$\left(q_{{\text{H}}_2}\right)$. Biohydrogen productivities and hydrogen to substrate yield (Y₍H_2/s₎)$\left(Y_{\left({\text{H}}_2/\text{s}\right)}\right)$ of C. saccharolyticus   on xylose in batch mode were higher working in a complex medium than in a defined one; but no significant difference could be settled according to hydrogen to carbon dioxide yields (Y₍H_2/CO₂₎)$\left(Y_{\left({\text{H}}_2/{\text{CO}}_2\right)}\right)$. The specific growth rate of C. saccharolyticus on complex medium was settled at 0.1 h⁻¹ operating in chemostat mode to achieve the highest H₂-productivities under stable conditions. In chemostat mode on xylose, a reduction of the ammonium feed concentration in a defined medium until N-limiting conditions involved higher qH₂$q_{{\text{H}}_2}$ comparing with a straight C-limiting growth.     

Folding screening assayed by proteolysis: application to various cystine deletion mutants of vascular endothelial growth factor

The production of recombinant proteins in Escherichia coli oftenleads to the formation of inclusion bodies. Although this hasa number of advantages, a major disadvantage is the need todevelop folding protocols for the renaturing of the proteins.However, the systematic screening of folding conditions is oftenhampered by the lack of convenient assays to detect correctlyfolded proteins. To address this problem we present a simpleprotocol, which combines folding screens and limited proteolysisto rapidly assess and optimize folding conditions. The efficacyof this method, termed FSAP (folding screening assayed by proteolysis),is demonstrated by the large-scale folding, purification andcrystallization of various cystine deletion mutants of the cystineknot family member: vascular endothelial growth factor (VEGF).These mutants are particularly difficult to fold as the cystineknot is believed to make major contributions to the stabilityof the protein and this family of proteins lacks extensive hydrophobiccore regions.     

Closing Water‐Related Loops in High‐tech Polymer Production – Status,Perspectives and Limitations

Chemical production is inherently associated with the use of a significant amount of water. The closure of water‐related loops to recover materials and reuse water has been established in chemical parks for a long time. Circuits can be realized process‐integrated, across legal entities, or even cross‐sectoral. Incentives can be the lack of natural water resources, to use a high water quality or the recovery of valuables. One example is the recovery of NaCl from salt‐containing process water streams to produce chlorine and caustic soda in the chlor‐alkali electrolysis. However, such reuse schemes exhibit technical, economic and ecological challenges. Taking these into account, industry is taking action to research and develop new, environmentally friendly and economically viable processes.     

Integration of product entropy and LCA to screen the potential environmental impacts of complex product systems at the end-of-life stage

Applying life cycle assessment (LCA) early in the development of technologies is essential to anticipate potential unforeseen environmental consequences. Modelling the lifecycle of a complex product is nevertheless challenging, as the data required is usually scarce. The approach presented in this paper integrates product entropy into end-of-life modelling for LCA. This enables anticipating the fate of a product after its end-of-use leading to a more realistic allocation of environmental impacts. The approach is demonstrated for the case study of recycling traction batteries with emerging traction battery cell chemistries.     

Bücherschau

Ohne Zusammenfassung VDI     

In Vivo Examination of an Injectable Hydrogel System Crosslinked by Peptide–Oligosaccharide Interaction in Immunocompetent Nude Mice

Hydrogels can serve as matrices to mimic natural tissue function and be used for wide‐ranging applications such as tissue regeneration and drug delivery. Injectable hydrogels are particularly favorable because their uses are minimally invasive. However, creating moldable substance for injection often results in compromised function and stability. This study reports an injectable hydrogel system crosslinked by peptide–oligosaccharide noncovalent interaction. The dynamic network shows fast self‐healing, a property essential for injectability. Injected hydrogels in immunocompetent mice and release of encapsulated compound are monitored up to 9 months by magnetic resonance imaging (MRI) and optical imaging. This surprisingly stable hydrogel does not cause adverse inflammatory response, as analyzed by measuring cytokine levels, immunohistochemistry, and MRI. Hydrogel degradation is associated with invasion of macrophages and vascular formation. The facile synthesis, high biocompatibility, and stability of this injectable hydrogel can lead to various experimental and clinical applications in regenerative medicine and drug delivery.