Natalie Rudolph

Phosphoglycerate kinase isozyme profile in reproductive cells and tissues of cattle: Sperm specificity of PGK-B

Two genetically independent isozymes of phosphoglycerate kinase (EC 2.7.2.3; ATP:3-phospho-D-glycerate 1-phosphotransferase; PGK) exist in mammals. PGK-A is the predominant, or only, PGK isozyme in somatic tissues, depending on the species, and it is X linked in humans, mice, and kangaroos (Chen et al., 1971; Kozak et al., 1974; VandeBerg et al., 1977). PGK-B, which is autosomally inherited in mice and kangaroos, is found only in therian mammals (VandeBerg et al., 1976, 1980). In most eutherian species, it is restricted to sperm and to those testes and epididymides that contain sperm (VandeBerg et al., 1973). Weak expression of PGK-B has been found in erythrocytes of dogs, foxes, and 28 of 43 marsupial species (VandeBerg et al., 1973). No evidence of a PGK-B isozyme has been found in cats or monotreme mammals (VandeBerg, 1975). We have examined PGK isozyme patterns in male and female gametes and in male reproductive tissues of Holstein cattle, and we present evidence that bovine PGK-B is expressed only in male germline cells.

Co-Curing of CFRP-Steel Hybrid Joints Using the Vacuum Assisted Resin Infusion Process

This study focuses on the one-step co-curing process of carbon fiber reinforced plastics (CFRP) joined with a steel plate to form a hybrid structure. In this process CFRP laminate and bond to the metal are realized simultaneously by resin infusion, such that the same resin serves for both infusion and adhesion. For comparison, the commonly applied two-step process of adhesive bonding is studied. In this case, the CFRP laminate is fabricated in a first stage through resin infusion of Non Crimp Fabric (NCF) and joined to the steel plate in a further step through adhesive bonding. For this purpose, the commercially available epoxy-based Betamate 1620 is applied. CFRP laminates were fabricated using two different resin systems, namely the epoxy (EP)-based RTM6 and a newly developed fast curing polyurethane (PU) resin. Results show comparable mechanical performance of the PU and EP based CFRP laminates. The strength of the bond of the co-cured samples was in the same order as the samples adhesively bonded with the PU resin and the structural adhesive. The assembly adhesive with higher ductility showed a weaker performance compared to the other tests. It could be shown that the surface roughness had the highest impact on the joint performance under the investigated conditions.

Processing of Poly(lactic Acid)

Polymer applications range from biomedical devices and structures, packaging, or toys to automotive and industrial items. So far, biopolymers could replace commodity polymers in a variety of products, especially for biomedical applications or food packaging. One of the most used and widely studied biopolymers is poly(lactic acid) (PLA). To generate new application fields and provide a broader application of PLA, research on processing behavior is still required. This chapter covers the processing relevant behavior of PLA and processing conditions for extrusion melt spinning, injection molding, and additive manufacturing. The processing-related behavior is compared to that of commodity polymers. The aim is to provide an overview of the state of the art and some recent new developments in this research field.

Phase Change Detection in Neat and Fiber Reinforced Polyamide 6 Using Dielectric Analysis

In this study online-capable dielectric analysis techniques were investigated to show its potential on the example of detecting phase transitions of polyamide 6 (PA6) and its composites. The differential scanning calorimetry (DSC), a standard testing method commonly applied in thermophysical analysis, is used as a reference method throughout this work. Dielectric measurement techniques are introduced as a means for providing an online measuring concept that is able to monitor phasechanges in both neat, as well as glass and carbon reinforced PA6. Whereas a simple sensor setup has proven to be adequate for dielectric measurements of neat and glass reinforced PA6, the insertion of an additional insulation layer between sample and sensor was necessary to overcome short circuit problems induced through the conductive nature of carbon in carbon fiber reinforced PA6.Results show that crystallization and melting can be successfully identified using dielectric analysis and can be compared directly with results from the DSC. Analysis in the dielectric method is based on relative permittivity ϵ′, loss factor ϵ′′ and ion viscosity ρ. Here phase changes can be observed as a frequency dependent step in the measurement signal, which becomes increasingly apparent with increasing frequency. Plotting the first derivative of ϵ′, ϵ′′ and ρ relative to the temperature the phase change can be depicted in form of a peak, similar to the case of DSC. The derivative signals can be used as a direct means for monitoring in manufacturing processes.