Cold Model Investigations of Melting of Ice in a Gas-Stirred Vessel

The melting of steel scrap in high temperature liquid iron melt is investigated by conducting cold model experiments of the melting of ice sample of different geometries and sizes in an argon-stirred vessel containing water. The melting process of ice samples is observed using a high-speed camera. Design of experiments is based on similarity criteria. The relationships between non-dimensional groups related to heat transfer (Nu, Re, Pr, and Gr) are derived for different experimental conditions. The results are compared with those reported in the literature. The heat transfer coefficient is estimated as a function of mixing power and is found to be in good agreement with the calculated values obtained by using reported relationships in literature.     

Hydrogen Embrittlement in a Plasma Tungsten Inert Gas-Welded Austenitic CrMnNi Stainless Steel

The study evaluates the effect of electrochemical hydrogen charging on the tensile properties and fracture behavior of the plasma tungsten inert gas weld of the high-alloy austenitic steel X3CrMnNiMoN17-8-4 in comparison to the pure base metal (BM). The weld metal exhibits a higher susceptibility to hydrogen embrittlement than the BM, which is mainly expressed by a loss in ductility. Based on the performed electron backscatter diffraction and X-ray diffraction examinations, this is attributed to the higher amount of δ-ferrite and the higher dislocation density in the weld zone. Furthermore, fractographic analyses reveal a change in the manner of fracture mode from ductile to brittle fracture starting from the edge in the hydrogen charged samples. The wider area of brittle fracture in the weld seam in relation to the BM indicates that hydrogen penetrates deeper into the material. Consequently, the diffusivity of hydrogen in the weld seam is determined to be significantly higher than in the BM.     

Experimental investigation of compact silicon carbide heat exchangers for high temperatures

The results of experimental investigations of novel ceramic high-temperature heat exchangers (HTHE) and its main characteristics such as effectiveness and power load as a function of mass flow and the geometry of the channels are presented. Firstly, some information on the background and the manufacturing of the HTHE, which is based on honey comb structures made out of extruded silicon carbide, is given. The experimental tests have been carried out with air as a heat transfer medium at temperatures of up to 1000 °C. The experimental set-up is described in detail. The acquired characteristic temperature and effectiveness data for different inlet temperatures and mass flows are discussed. They have been compared with data from theoretical calculations as well as with characteristic data of typical counter flow heat exchangers. Additionally, thermal shock tests have been carried out for a qualitative testing of the mechanical strength. Finally, a conclusion and an outlook on further activities are given.     

Influence of carbon fibre on formation kinetics of crosslinked copolymer from bisphenol A dicyanate and epoxy oligomer

The influence of carbon fibre on the curing kinetics of the prepolymer based on bisphenol A cyanurate and epoxy resin has been studied using infra-red spectroscopy. It was found that the curing process of the prepolymer is very complicated. It is shown that in curing the prepolymer a number of the sequential transformations of one ring structure into others occurs. An introduction of the carbon fibre (CF) of two types, original CF and modified CF (MCF) containing phosphate groups, affects strongly the prepolymer curing. Both CF and MCF accelerate the conversion rate of epoxy groups. In the case of cyanate groups, the former has practically no effect on their conversion whereas the latter decelerates strongly this process. In the present paper the influence of CF on the mechanism of the copolymer formation is considered.     

Collagen Structural Hierarchy and Susceptibility to Degradation by Ultraviolet Radiation

Collagen type I is the most abundant extracellular matrix protein in the human body, providing the basis for tissue structure and directing cellular functions. Collagen has complex structural hierarchy, organized at different length scales, including the characteristic triple helical feature. In the present study, the relationship between collagen structure (native vs. denatured) and sensitivity to UV radiation was assessed, with a focus on changes in primary structure, changes in conformation, microstructure and material properties. A brief review of free radical reactions involved in collagen degradation is also provided as a mechanistic basis for the changes observed in the study. Structural and functional changes in the collagens were related to the initial conformation (native vs. denatured) and the energy of irradiation. These changes were tracked using SDS-PAGE to assess molecular weight, Fourier transform infrared (FTIR) spectroscopy to study changes in the secondary structure, and atomic force microscopy (AFM) to characterize changes in mechanical properties. The results correlate differences in sensitivity to irradiation with initial collagen structural state: collagen in native conformation vs. heat-treated (denatured) collagen. Changes in collagen were found at all levels of the hierarchical structural organization. In general, the native collagen triple helix is most sensitive to UV-254nm radiation. The triple helix delays single chain degradation. The loss of the triple helix in collagen is accompanied by hydrogen abstraction through free radical mechanisms. The results received suggest that the effects of electromagnetic radiation on biologically relevant extracellular matrices (collagen in the present study) are important to assess in the context of the state of collagen structure. The results have implications in tissue remodeling, wound repair and disease progression.     

FcγRs and Their Relevance for the Activity of Anti-CD40 Antibodies

Simple SummaryTargeting of CD40 with antibodies attracts significant translational interest. While inhibitory CD40 targeting appears particularly attractive in the field of organ transplantation and for the treatment of autoimmune diseases, stimulatory CD40 targeting is the aim in tumor immunotherapy and vaccination against infectious pathogens. It turned out that lack of FcγR-binding is the crucial factor for the development of safe and well-tolerated inhibitory anti-CD40 antibodies. In striking contrast, FcγR-binding is of great importance for the CD40 stimulatory capacity of the majority of anti-CD40 antibodies. Typically, anti-CD40 antibodies only robustly stimulate CD40 when presented by FcγRs. However, FcγR-binding of anti-CD40 antibodies also triggers unwanted activities such as destruction of CD40 expressing cells by ADCC or ADCP. Based on a brief discussion of the mechanisms of CD40 activation, we give an overview of the ongoing activities in the development of anti-CD40 antibodies under special consideration of attempts aimed at the development of anti-CD40 antibodies with FcγR-independent agonism or FcγR subtype selectivity.AbstractInhibitory targeting of the CD40L-CD40 system is a promising therapeutic option in the field of organ transplantation and is also attractive in the treatment of autoimmune diseases. After early complex results with neutralizing CD40L antibodies, it turned out that lack of Fcγ receptor (FcγR)-binding is the crucial factor for the development of safe inhibitory antibodies targeting CD40L or CD40. Indeed, in recent years, blocking CD40 antibodies not interacting with FcγRs, has proven to be well tolerated in clinical studies and has shown initial clinical efficacy. Stimulation of CD40 is also of considerable therapeutic interest, especially in cancer immunotherapy. CD40 can be robustly activated by genetically engineered variants of soluble CD40L but also by anti-CD40 antibodies. However, the development of CD40L-based agonists is biotechnologically and pharmacokinetically challenging, and anti-CD40 antibodies typically display only strong agonism in complex with FcγRs or upon secondary crosslinking. The latter, however, typically results in poorly developable mixtures of molecule species of varying stoichiometry and FcγR-binding by anti-CD40 antibodies can elicit unwanted side effects such as antibody-dependent cellular cytotoxicity (ADCC) or antibody-dependent cellular phagocytosis (ADCP) of CD40 expressing immune cells. Here, we summarize and compare strategies to overcome the unwanted target cell-destroying activity of anti-CD40-FcγR complexes, especially the use of FcγR type-specific mutants and the FcγR-independent cell surface anchoring of bispecific anti-CD40 fusion proteins. Especially, we discuss the therapeutic potential of these strategies in view of the emerging evidence for the dose-limiting activities of systemic CD40 engagement.     

Template synthesis,structure, sorption properties and acidity of micro-mesoporous materials obtained from sol-precursor of zeolite BEA

Partially zeolitized micro-mesoporous materials (the total specific surface area S _BET  = 460–645 m²/g, mesopore volume V _meso  = 0.30–0.57 cm³/g, mesopore diameter D _meso  ≈ 5.6 nm, micropore volume V _micro  = 0.11–0.16 cm³/g, micropore diameter D _micro  ≈ 0.72 nm) and X-ray amorphous micro-mesoporous materials with uniform mesoporous structure (mesopore specific surface area S _meso  = 820–890 m²/g, total pore volume V _t  = 0.71–0.86 cm³/g, V _meso  = 0.53–0.67 cm³/g, D _meso  = 1.8–2.4 nm) were obtained by micellar templating of sol-precursor containing primary products of crystallization of zeolite BEA under conditions typical for forming of mesoporous molecular sieve MCM-41 (hydrothermal treatment at 100–130 °C for 3–5 days). It was found that the obtained X-ray amorphous micro-mesoporous materials contain secondary building units of zeolite BEA (five-membered rings of Si–O tetrahedra of BEA) and show acidic properties comparable to zeolite BEA.