Ageing mechanisms on PdOx-based catalysts for natural gas combustion in premixed burners

The ageing effect induced by S-compounds over 2%Pd/CeO₂·2ZrO₂, 2%Pd/LaMnO₃·2ZrO₂ and 2%Pd/BaCeO₃·2ZrO₂ catalysts for CH₄ combustion was investigated; S-compounds are in fact added as odorants in the natural gas network for safety purposes. Pd-based catalysts were prepared by solution combustion synthesis (SCS), starting from metal nitrates/glycine mixtures. Basic characterization (XRD, BET, FESEM analysis), FT–IR studies and catalytic activity tests were performed on powders and after accelerated ageing carried out up to 2 weeks (hydro-thermal treatment at 900 °C under a flow rate with typical domestic boiler exhaust gas composition, 9% CO₂, 18% H₂O, 2% O₂ in N₂, containing also 200 ppmv of SO₂ to emphasize any poisoning effect). Over fresh catalysts, IR analysis of CO adsorption evidenced the formation of highly dispersed Pd metal clusters and Pd ions. With ageing, 2%Pd/CeO₂·2ZrO₂ increased its CH₄ combustion half-conversion temperature (T₅₀, regarded as an index of catalytic activity) from 382 °C—recorded for fresh sample—to 421 °C, attained with the same sample aged two weeks. An unexpected improvement was found instead in the overall performance of 2%Pd/LaMnO₃·2ZrO₂ and 2%Pd/BaCeO₃·2ZrO₂: the T₅₀ in fact lowered from 570 to 450 °C for the first one, and from 512 to 443 °C for the second one, after two weeks ageing. S-hydro-thermal treatment provoked bulk and surface sulfates formation on all aged samples, with a concentration increasing with the exposure time. Prevailing ageing mechanisms seemed to be Pd metallic clusters coalescence, detected over the Ce–Zr system, and surface-bulk sulfates formation, the latter destroying the initial crystallographic structure. In 2%Pd/LaMnO₃·ZrO₂ and 2%Pd/BaCeO₃·ZrO₂ powders the amount of the perovskite phase strongly decreased during ageing, in favor of the formation of bulk sulfate and of oxides.     

Hydrous pyrolysis of silica-supported polystyrene

Thermal degradation of polystyrene has been studied in the presence of water under subcritical conditions (hydrous pyrolysis). The experiments were performed in closed systems under inert atmosphere, in the temperature range of 300–320°C, for 1–24 h. The results showed that the presence of water increases the yields of the volatile products, mainly in the first steps of the pyrolitic process, with a higher selectivity of monomer. In order to improve the effective phase contact between water and the polymer during the degradation, hydrous pyrolysis runs have been carried out on silica-supported polystyrene. Some of these experiments were performed using a stirred reactor. Under these conditions, the above effects appeared to be greatly emphasized. Qualitative and quantitative analyses of the degradation products have been reported for the series of runs investigated. The best recovery of styrene has been achieved at 320°C and 8 h, being close to 71%. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 70: 2291–2298, 1998     

Perceived importance of fuel characteristics and its match with consumer beliefs about biofuels in Belgium

Consumer consciousness concerning the environment has increased and become a major factor in purchasing behaviour. Consumer research to understand and influence the adoption of green technologies and products is therefore important. This paper investigates the beliefs of Belgian consumers concerning the use of biofuels and identifies four consumer segments based on the perceived importance of different fuel characteristics. To convince the performance-oriented consumers to use biofuels, information about these fuels has to stress their quality and performance standards. The society-oriented cluster attaches great importance to environmental friendliness, odour, production origin, the opportunity to decrease energy dependency and job creation. To persuade the environment-oriented consumers low odour, beneficial environmental influence and quality assurance of biofuels have to be emphasized. The convenience-oriented consumers will be the most difficult to persuade to use biofuels. They need to be convinced that every vehicle can drive with biofuel blends without the need for engine modifications. Concerns relating to the price and perceived low availability of biofuels at fuel stations are major obstacles for all consumers involved in this study.     

Ein neues Verfahren zur Bestimmung von minderwertigen Mehlen in Weizenmehl

Ohne ZusammenfassungMitteilung aus dem Hygienischen Institut der Kgl. Universität Turin. (Direktor: Prof. Dr. L. Pagliani.)     

Zustandsformen von Verbundnetzen

A set of state equations, needed for stability analysis of interconnected electric power systems, is difficult to determine for large grids. These equations can be set up by calculating the state equations for every individual transmission system and joining them to the interconnected system afterwards. This algorithm avoids privacy problems, which can result from data exchange with other transmission system operators in the free electricity market. No competition-relevant data, which would allow conclusions to be drawn regarding the individual grid structure, are passed on.     

Potential impact of medium characteristics on the isomerisation of hop α-acids in wort and buffer model systems

Many brewing variables, e.g., pH, boiling time, temperature, and the presence of metal catalysts, are essential in view of the isomerisation of hop α-acids into iso-α-acids. In this work, a comparative study on the impact of several selected factors on α-acids isomerisation was performed in both buffer model solutions and wort, in order to find out enhanced boiling conditions for higher isomerisation yields.     

A dynamic load balancing algorithm for Quality of Service and mobility management in next generation home networks

Heterogeneity of connection technologies and nodes mobility open new challenges in home networks control strategies. Moreover, user’s needs are changing towards applications requiring high transmission speeds such as 3D gaming, enhanced interactivity and high definition video. Each of those applications puts several constraints on the network capabilities to guarantee requirements on the Quality of Service. In this paper we introduce an innovative concept based on fast load balancing algorithm operating on top of a convergence layer, in order to rapidly react to network changes and contemporaneously to satisfy strict application demands. We formulated the load balancing problem as a Multi-Commodity Flow and resolved it with a column generation approach using Lagrangian Relaxation and Dijkstra algorithm. The load balancing problem computational complexity is decreased with respect to state of the art load balancing solutions based on linear programming techniques. Proof of concept simulation results are reported.     

Optical Network Survivability: Protection Techniques in the WDM Layer

This paper is an introduction to survivability of WDM networks. All the main optical protection techniques proposed as far as now for the WDM layer are classified and reviewed. In particular, commonly adopted protection strategies for ring and mesh networks are explained. Moreover, off-line planning of WDM networks able to support path protection is briefly introduced. Finally, an example of heuristic network-capacity optimization is presented, discussing results obtained by considering a case-study network.     

Medical device labeling and advertising: an overview

The Food and Drug Administration (FDA) has the authority under the Federal Food, Drug, and Cosmetic Act (FDCA) to regulate the labeling of all medical devices. This statement, however, is not as simple as it appears. The regulation of medical device labels and labeling, closely linked to the advertisement of medical devices, is a dynamic area, and FDA is struggling to address the new issues that arise daily in this area. This article seeks to: 1) provide the background necessary to understand the current law and FDA's regulation of medical devices; 2) summarize the law and regulations governing medical devices; 3) define "intended use" and explain its importance; and 4) discuss several areas that are of particular interest to FDA, including promotion of uncleared or unapproved devices and uses, Internet promotion, press releases, and comparative claims.     

Effect of corticotropin-releasing factor on the pituitary-ovary axis in human luteal phase

In order to test the possible negative effect of corticotropin-releasing factor (CRF) on the pituitary-gonadal axis, two gonadotropin-releasing hormone (GnRH) tests, on two consecutive days, were performed in five normally cycling women in the midluteal phase of the menstrual cycle. The first GnRH test was performed after 2 h during which time basal blood samples were collected every 10 min. On the second day, the GnRH test was repeated after a 2-h CRF infusion which was continued throughout the GnRH test. Our results demonstrate that while CRF increases cortisol levels it affects neither the basal nor the GnRH-stimulated gonadotropin levels. Similarly, both basal and luteinizing hormone (LH)-stimulated progesterone concentrations were not modified by the CRF infusion thereby also excluding a possible direct effect of the peptide on corpus luteum steroidogenesis.