Hydrosilylation crosslinking of silicone rubber catalyzed by bis (1,5-cyclooctadiene) di-μ,μ′-chlorodirhodium

Hydrosilylation vulcanization of addition silicone rubber catalyzed by bis (1,5-cyclooctadiene) di-μ,μ′-chlorodirhodium at 150° was studied. The course of vulcanization, rubber network density, and mechanical properties of the vulcanizate are discussed with respect to the structure and molecular weight of the reactive groups of telechelic and internal vinylmethylpolysiloxanes and crosslinking methyl (hydrogen) dimethyl siloxane copolymers. Molecular weights of the polysiloxane components as well as the ration of unsaturated and Si—H groups were optimized. The results are in agreement with the theory of rubber elasticity of polymer networks and show wide application possibilities of the catalyst used.     

Evaluating the effect of year of seroconversion on HIV progression in cohort studies. Italian Seroconversion Study

OBJECTIVES: To show how a spurious association between the calendar year of seroconversion and HIV progression arises as a result of censoring the follow-up of individuals at their last visit, when the individuals' visits are intermittent. DESIGN: A notional cohort of 1140 seroconverters and a cohort study of 1270 HIV-infected individuals seroconverted between 1985 and 1994, and followed up to December 1995 (the Italian Seroconversion Study cohort). METHODS: Failure times and rate of the patients attending the clinic over the study period were simulated for the notional cohort. Three separate scenarios with different probabilities of making a visit were considered. Standard survival analysis techniques were used to assess the effect of the year of seroconversion on HIV progression. The progression to a CD4 cell count of 200 x 10(6)/l according to the calendar year of seroconversion in the Italian Seroconversion Study was assessed using different censoring strategies. RESULTS: A spurious effect of the year of seroconversion consistently appeared in 100 repeated simulations. When ignoring the visits occurring after the first year of follow-up in the Italian Seroconversion Study cohort, results supported the hypothesis of no effect of the year from seroconversion. CONCLUSIONS: The choice of the censoring strategy is crucial when assessing the effect of year of seroconversion using survival analysis in cohort studies with intermittent visit structure. Different censoring strategies should be considered before firmly concluding that more virulent strains or the use of treatment are modifying the natural history of HIV disease from cohort studies of this nature.     

Complex structure and catalytic hydrogen ion reduction in Ni (II)-glutathione system

Polarographic studies on the reduction of hydrogen ions in the presence of Ni(II)-glutathione complexes revealed for alkaline solutions two catalytic waves. The catalytic reduction of hydrogen occurs only in the presence of square planar complexes which seem to be responsible for the catalysis. Besides the planar structure the metal-sulphur bond is necessary for the latter process.     

Application of a polymerase chain reaction (PCR) method as a complementary tool to microscopic analysis for the detection of bones and other animal tissues in home‐made animal meals

A polymerase chain reaction (PCR) method was compared with a variation of the official microscopic technique (Directive 98/88/EC) for the detection in animal meals of cereals (wheat and corn) and animal parts (bone, feathers, meat, liver, fat and blood). Microscopy successfully detected animal bones in raw feeds with a sensitivity of 1 g kg^?1, while the sensitivity of the PCR method was in the range of 5–10 g kg^?1. Microscopy also allowed the detection of animal bones and feathers in feeds processed at 115 and 133 °C but failed to detect other animal materials. The PCR method successfully detected cereals (wheat and corn) as well as meat, bone, liver, fat and feathers after processing at 115 °C for 20 min. Heating at 133 °C under overpressure (autoclave) conditions resulted in more intense DNA fragmentation and lower DNA extractability. Nevertheless, bone and liver, as well as wheat and corn in home‐made animal meals, were successfully detected even after heating at 133 °C for 20 min. Copyright © 2004 Society of Chemical Industry     

Handover defects: comparison of construction and post-handover housing defects

Although inspections occur during construction or at handover, customers do not normally participate. This situation creates a gap between the quality perceived by both contractors and customers. An analysis of 52 552 handover defects in 2179 flats in Spain is presented which identified their nature, the building element and trade where these defects are located. These results are compared with previous studies that analysed defects detected during the construction stage and those that remain after handing over the building to the client. The research reveals that structural defects are resolved during construction due to existing quality standards. However, other aesthetic and functional defects remain and/or arise at handover. Some defects are not resolved until customers complain after they first occupy the dwelling. Many functional defects arise due to the lack of involvement of end users in the early project stages.     

Microstructure, dielectric and electromechanical properties of PLSZFT nanoceramics for piezoelectric applications

This investigation highlights the influence of isovalent Sr²⁺ on acceptor Fe³⁺ modified PLZT for microstructure and its effect on dielectric and piezoelectric properties [Pb_0.985−yLa_0.015Sr_y][(Zr_0.538Ti_0.462)_0.985Fe_0.015]O₃ where y = 0, 0.5, 1.0, and 1.5 mol% nanocrystalline solid solutions near morphotrophic phase boundary were synthesized by solid state reaction method. X-ray diffraction patterns indicated that Sr increment resulted in strong tetragonality. Grain size and apparent density enhanced up to y = 1.5 mol%. TEM studies indicated that average particle size ranged from 23 to 68 nm. PLSZFT compositions attained optimum ε_RT, d₃₃, and k_p at y = 1.5 mol%, respectively which could be suitable for possible piezoelectric applications. The influence of grain size on dielectric and piezoelectric properties are reported.     

New Spectrophotometric System to Segregate Tissues in Mandarin Fruit

The knowledge of the electrical properties of the fruit tissues and their relation with the structural and compositional properties opens an endless number of opportunities in the development and design of industrial equipment for quality and process control. Nowadays, one of the main industrial issues is the detection of seeds inside the fruit, which could be possible with an electrical study of each tissue as a first step of the development of non-destructive sensors. In this context, a deep study of the dielectric properties of mandarin fruit tissues, coupled with a _w, X _w, pH, maturity index, cryo-SEM, and optical measurements, was performed. Dielectric properties were studied in radiofrequency and microwave ranges. α-, β-, and γ-dispersions and their relaxation parameters were obtained, described, and related to the chemical parameters. Finally, a tool, based on the relaxation dielectric constant in γ-dispersion able to determine the moisture content of the mandarin fruit tissues, has been developed.     

Incorporating a Systemic and Foresight Approach into Smart City Initiatives: The Case of Spanish Cities

At the dawn of the twenty-first century, cities face serious societal, economic, environmental, and governance challenges. Under the term “Smart City,” numerous technology-based initiatives are emerging to help cities face contemporary challenges while the concept itself is evolving towards a more holistic approach. Nevertheless, the capability of smart initiatives to provide an integrated vision of our cities is still very limited. Eventually, many of these initiatives do not fulfill satisfactorily their initial objectives because they fail to understand the complexity, diversity, and uncertainty that characterize contemporary cities. The purpose of this paper is twofold: to display an urban functional system, capable of interpreting the city in a more holistic way, and to incorporate foresight tools so as to formulate Smart City visions in a more participatory way with the involvement of local stakeholders.     

Adsorption of natural gas and biogas components on activated carbon

Experimental results are presented for the adsorption equilibria of methane, ethane, propane, butane, carbon dioxide, and nitrogen, as well as natural gas odorants tert-butyl mercaptan and tetrahydrothiophene, on an activated carbon with the desirable characteristics for use in a guard bed for adsorbed natural gas storage, but that can also be applied for separation of biogas components, such as carbon dioxide and nitrogen. The adsorption experiments were performed using both open- and closed-loop gravimetry over the pressure and temperature ranges of 0–9 MPa and 273–325 K, respectively. The two odorants were analyzed at the very low concentrations usually found in natural gas (0–25 mg/(N m³)). The experimental data were successfully correlated by the adsorption potential theory and collapsed into a single temperature-independent characteristic curve. This analysis allows for extrapolation of the adsorption data to higher alkanes, for which no experimental data are available, in order to span the global composition of a typical natural gas stream. The adsorption equilibrium data for methane, carbon dioxide and nitrogen were fitted to the Toth and Sips isotherm models and their isosteric heats of adsorption were determined. The preferential adsorption capacity for carbon dioxide indicates that the carbon can be used for methane purification from natural gas, carbon dioxide sequestration from flue gas, or biogas purification.