Reactivity and stability of Ni/Al2O3 oxygen carrier for chemical-looping combustion (CLC)

Chemical-looping combustion (CLC) is a technology that reduces the carbon dioxide emissions from fossil fuel power stations. A nickel supported on -alumina oxygen carrier is investigated in this study, for use in a CLC process. Oxygen carriers with various nickel loadings on alumina are prepared according to the incipient wetness technique. The reactivity and stability of the prepared oxygen carrier samples, during repeated reduction–oxidation cycles, is demonstrated using temperature programmed reduction and oxidation. Pulse chemisorption results show that the dispersion and active crystallite diameter of the nickel particles remain constant over multiple reduction–oxidation cycles, indicating that no agglomeration occurs up to a nickel loading of 20 wt% supported on alumina. The stability and reactivity of the oxygen carriers, under industrial relevant conditions, are also investigated using the CREC fluidized bed riser simulator. It is observed that a 20 wt% nickel supported on alumina oxygen carrier is stable under industrial relevant fluidized bed reaction conditions, converting 76% of methane to carbon dioxide and water vapor, the combustion products. The metal support interaction is assessed by H₂ temperature programmed desorption, which shows that the metal-support interaction decreases as more nickel is loaded onto the alumina support.     

Post-war public high-rise housing estates: What went wrong with housing policy,with the design and with management?

Journal of Housing and the Built Environment -     

Efficient microcoded processor design for fixed rate DFT and FFT

Many Fourier transform applications have to operate at fixed sample rates in the low to medium range, especially in signal processing systems. Hence, in order to arrive at efficient implementations, hardware-sharing is required as in microcoded architectures. In this paper, very efficient application-specific realizations spanning a wide throughput range are proposed for both DFT and FFT algorithms. Novel single-cycle address computations are presented for the FFT to obtain these results. Trade-offs between the architectural alternatives are provided too. These designs have been used as test-vehicles for the architectural strategy in an automated synthesis tool-box tuned towards signal processing applications.This research has been sponsored in part within the context of the ESPRIT97 project by the EC and the industrial partners Philips, Siemens, BTMC/Alcatel and Silvar/Lisco.     

Möglichkeiten und Problemlösungen der Stromerzeugung mit Windkraftwerken

Scope and problem solutions of power generation by wind-driven plant. The importance of wind power has changed in the course of history with the advent of competing energy converters for power production from coal, oil, and nuclear energy. The known physical laws of aerodynamics and geographical location ascribe wind power a market share of no more than a few percent of power generation. Among the many designs of wind turbines, only 2- and 3-blade propeller turbines have been produced in large quantities with power ratings up to ca. 4 MW. Market developments have so far been determined by government funding. The power generation costs of 0.25 to 0.30 DM/kWh are still too high by a factor of 2 to 3. With regard to future developments it remains to be seen whether the use of more sophisticated generator systems will permit the expected large savings on the mechanical side and thus open the path to economic large production runs also in the case of medium and large-scale units.     

Impact of Volume Fraction and Size of Reinforcement Particles on the Grain Size in Metal–Matrix Micro and Nanocomposites

In metal–matrix micro and nanocomposites (MMCs and MMNCs), the presence and interactions of various strengthening mechanisms are not well understood, but grain boundary strengthening is considered as one of the primary means of improving the yield strength of composites. Owing to the importance of grain size on mechanical properties, it is necessary to be able to describe how incorporation of nanoparticles (NPs) in both powder metallurgy (PM) and solidification processing (SP) affects this critical property. In the present work, we provide a basis for an empirical equation that relates particle fraction and particle size to MMNC grain size for both PM and SP synthesis methods. The model suggests that NPs retard grain coarsening in PM MMNCs and also seems to describe the effect of reinforcement concentration on grain size in SP MMCs and MMNCs.     

Lactobacillus delbrueckii subsp lactis strain CIDCA 133 inhibits nitrate reductase activity of Escherichia coli

The aim of the present work was to investigate the effect of strain CIDCA 133 on the nitrate reductase activity of a non-pathogenic Escherichia coli strain. Suspensions containing different ratios of the strains under study were coincubated in MRS or MRS without glucose. In some experiments lactobacilli were killed by UV treatment. The nitrate reductase activity was determined by using a diazotization reaction for nitrite. Presence of live lactobacilli leads to a dose-response diminution in the specific nitrate reductase of E. coli even when no acidification occurred. Killing of lactobacilli by UV treatment completely abolished the anti-nitrate reductase effect. In addition, the effect was only partially observed with filtered spent culture supernatants of lactobacilli. Lactobacillus delbrueckii subsp lactis strain CIDCA 133 is able to antagonize the nitrate reductase activity of E. coli. This effect is neither due to a diminution of the viability of E. coli nor is depending on the acidification of the medium by the lactobacilli. Viability is needed for maximal anti-nitrate reductase activity. Modulation of undesirable enzymatic activities of intestinal microorganisms by means of selected microorganisms constitutes a further insight on the mechanisms by which probiotics lead to beneficial effects. Administration of probiotic strains able to modulate microbial intestinal activities could lead to a protection of the host against harmful effects of some members of the intestinal microflora.     

Development of an antimicrobial material based on a nanocomposite cellulose acetate film for active food packaging

Nanocomposites based on biopolymers have been recognised as potential materials for the development of new ecofriendly food packaging. In addition, if these materials incorporate active substances in their structure, the potential applications are much higher. Therefore, this work was oriented to develop nanocomposites with antimicrobial activity based on cellulose acetate (CA), a commercial organoclay Cloisite30B (C30B), thymol (T) as natural antimicrobial component and tri-ethyl citrate (TEC) as plasticiser. Nanocomposites were prepared by a solvent casting method and consisted of 5% (w/w) of C30B, 5% (w/w) of TEC and variable content of T (0%, 0.5% and 2% w/w). To evaluate the effect of C30B into the CA matrix, CA films without this organoclay but with T were also prepared. All nanocomposites showed the intercalation of CA into the organoclay structure; furthermore this intercalation was favoured when 2% (w/w) of T was added to the nanocomposite. In spite of the observed intercalation, the presence of C30B inside the CA matrices increased the opacity of the films significantly. On the other hand, T showed a plasticiser effect on the thermal properties of CA nanocomposites decreasing glass transition, melting temperature and melting enthalpy. The presence of T in CA nanocomposites also allowed the control de Listeria innocua growth when these materials were placed in contact with this Gram-positive bacterium. Interestingly, antimicrobial activity was increased with the presence of C30B. Finally, studies on T release showed that the clay structure inside the CA matrix did not affect its release rate; however, this nanofiller affected the partition coefficient K_P/FS which was higher to CA nanocomposites films than in CA films without organoclay. The results obtained in the present study are really promising to be applied in the manufacture of food packaging materials.     

Comparative sequence analysis of spa gene of Staphylococcus aureus isolated from bovine mastitis: characterization of an unusual spa gene variant

The protein A encoding gene spa of four Staphylococcus aureus strains isolated from bovine clinical mastitis was amplified by PCR and sequenced. The four strains were selected after an initial screening of spa gene of 41 strains isolated from mastitic cows and were subjected to detailed investigations. According to the sequencing results the spa gene of three strains (M1, M2, M3) appeared with gene segments encoding five (E, D, A, B and C) and four (E, A, B and C) IgG binding domains for two (M1, M3) and one (M2) strain, respectively and with gene segments encoding four, two and two repeats of the octapeptide Xr-repeats for the strains M1, M2 and M3, respectively. For the remaining Staph. aureus strain (M4) gene segments encoding IgG binding domains E, D and A and a new domain BC with a size of 219 bp could be observed. The BC domain appears, with a deletion of a 123 bp segment from the border region between both domains, as fused domain of both previously characterized domains. The Xr-region of this strain had 11 octapeptide repeats.