Textile fiber-reinforced anionic polyamide-6 composites. Part I: The vacuum infusion process

In order to manufacture thicker, larger and more integrated thermoplastic composite parts than currently can be achieved by melt processing, a vacuum infusion process is currently being developed at the Delft University of Technology using a reactive thermoplastic polymer called anionic polyamide-6 (APA-6). In previous studies it was demonstrated that the anionic polyamide-6 (APA-6) resin that is used has excellent mechanical properties. The present study assesses infused thermoplastic composites and focuses on fiber-matrix interactions. Part I of this study focuses on the thermal effects, causes for deactivation of the initiator and the restriction caused by the low in-plane permeability of the fiber textiles on various transport phenomena. It will be shown that addition of pre-heated fibers not only shortens the infusion window, but also influences the matrix properties by reducing the exothermic heat production. In addition, the low in-plane permeability of the fiber textiles influences the infusion time and causes the entrapment of voids. Finally, reactions between the matrix and the fiber surface can lead to deactivation of the initiator and bond formation with the activator. Interfacial bonding, however, is discussed in more detail in Part II of this study, whereas the effect of adding a nucleating agent is discussed in Part III.     

Heterologous expression of rat epitope-tagged histamine H2 receptors in insect Sf9 cells

1. Rat histamine H2 receptors were epitope-tagged with six histidine residues at the C-terminus to allow immunological detection of the receptor. Recombinant baculoviruses containing the epitope-tagged H2 receptor were prepared and were used to infect insect Sf9 cells. 2. The His-tagged H2 receptors expressed in insect Sf9 cells showed typical H2 receptor characteristics as determined with [125I]-aminopotentidine (APT) binding studies. 3. In Sf9 cells expressing the His-tagged H2 receptor histamine was able to stimulate cyclic AMP production 9 fold (EC50=2.1+/-0.1 microM) by use of the endogenous signalling pathway. The classical antagonists cimetidine, ranitidine and tiotidine inhibited histamine induced cyclic AMP production with Ki values of 0.60+/-0.43 microM, 0.25+/-0.15 microM and 28+/-7 nM, respectively (mean+/-s.e.mean, n=3). 4. The expression of the His-tagged H2 receptors in infected Sf9 cells reached functional levels of 6.6+/-0.6 pmol mg(-1) protein (mean+/-s.e.mean, n=3) after 3 days of infection. This represents about 2 x 10(6) copies of receptor/cell. Preincubation of the cells with 0.03 mM cholesterol-beta-cyclodextrin complex resulted in an increase of [125I]-APT binding up to 169+/-5% (mean+/-s.e.mean, n=3). 5. The addition of 0.03 mM cholesterol-beta-cyclodextrin complex did not affect histamine-induced cyclic AMP production. The EC50 value of histamine was 3.1+/-1.7 microM in the absence of cholesterol-beta-cyclodextrin complex and 11.1+/-5.5 microM in the presence of cholesterol-beta-cyclodextrin complex (mean+/-s.e.mean, n=3). Also, the amount of cyclic AMP produced in the presence of 100 microM histamine was identical, 85+/-18 pmol/10(6) cells in the absence and 81+/-11 pmol/10(6) cells in the presence of 0.03 mM cholesterol-beta-cyclodextrin complex (mean+/-s.e.mean, n=3). 6. Immunofluorescence studies with an antibody against the His-tag revealed that the majority of the His-tagged H2 receptors was localized inside the insect Sf9 cells, although plasma membrane labelling could be identified as well. 7. These experiments demonstrate the successful expression of His-tagged histamine H2 receptors in insect Sf9 cells. The H2 receptors couple functionally to the insect cell adenylate cyclase. However, our studies with cholesterol complementation and with immunofluorescent detection of the His-tag reveal that only a limited amount of H2 receptor protein is functional. These functional receptors are targeted to the plasma membrane.     

Optimal data gathering paths and energy-balance mechanisms in wireless networks

This paper studies the data gathering problem in wireless networks, where data generated at the nodes has to be collected at a single sink. We investigate the relationship between routing optimality and fair resource management. In particular, we prove that for energy-balanced data propagation, Pareto optimal routing and flow maximization are equivalent, and also prove that flow maximization is equivalent to maximizing the network lifetime. We algebraically characterize the network structures in which energy-balanced data flows are maximal. Moreover, we algebraically characterize communication links which are not used by an optimal flow. This leads to the characterization of minimal network structures supporting the maximal flows.We note that energy-balance, although implying global optimality, is a local property that can be computed efficiently and in a distributed manner. We suggest online distributed algorithms for energy-balance in different optimal network structures and numerically show their stability in particular setting. We remark that although the results obtained in this paper have a direct consequence in energy saving for wireless networks they do not limit themselves to this type of networks neither to energy as a resource. As a matter of fact, the results are much more general and can be used for any type of network and different types of resources.     

Dynamics of Hollow and Solid Alumina Particle Formation in Spray Flames

Thermophoretic sampling (TS) of the aerosol was conducted to manifest the formation of hollow and solid alumina particles in spray flames. The collected particles were investigated by transmission electron microscopy. Hollow particles with a thin shell (e.g., 10 nm) were formed from the aluminum nitrate precursor emulsion at less than 4-cm flame height. Hollow particles maintained their shapes in the flame using air as dispersion/oxidant gas, whereas hollow-to-solid restructuring of the particles took place in the flame using oxygen. With oxygen, nanoparticles were formed in the gas phase from the aluminum butoxide/2-propanol precursor solution only, whereas gas-phase reaction was hindered, forming large particles from the aluminum nitrate/2-propanol precursor solution.     

Integration of Mechanics and Acoustics in a Sandwich Fuselage. Part IV

Until now only the stiffened skin structural concept has been discussed. A different structural concept is the sandwich concept. Sandwiches consist out of layers. The outer layers are called facings and are generally thin and of high density. These facings are supposed to resist most of the edgewise loads and flat-wise bending moments. The inner layer is called the core and is generally rather thick and of low density. The task of the core is to separate and stabilize the two facings, transmit shear between the facings and provide most of the shear rigidity. For sandwich panels no stiffeners are needed. Therefore no mass will be lost in stiffeners resulting in a relative high value of mass per unit area of the skin which results in a better TL according to the mass law. Also the core can be made of a material with high insulation properties (acoustic and thermal). The number of discrete stiffeners can then be minimized, since they are only required at places where high concentrated forces have to be introduced (wing, landing gear, etc.) or diverted (from cut-outs). This can reduce the production and maintenance cost. So it can be concluded that the sandwich concept offers great potential for multidisciplinary fuselage design. In this part the integration of structural and acoustical aspects will be discussed. First the structural aspect will be discussed followed by the acoustical aspect. Finally the possibilities to integrate these aspects are explained.     

Flame-Made Pt/K/Al2O3 for NO x Storage–Reduction (NSR) Catalysts

High surface area Pt/K/Al₂O₃ catalysts were prepared with a 2-nozzle flame spray method resulting in Pt clusters on γ-Al₂O₃ and amorphous K storage material as evidenced by Raman spectroscopy. The powders had a high NO _x storage capacity and were regenerated fast in a model exhaust gas environment. From 300 to 400 °C no excess NO _x was detected in the off gas during transition from fuel lean to fuel rich conditions, resulting in a highly effective NO _x removal performance. Above 500 °C, the NSR activity was lost and not recovered at lower temperatures as K-compounds were partially crystallized on the catalyst.