Preparation and catalytic efficiency of mixed noble metal catalysts on electrochemically activated carbon fibre supports

Mixed noble metal catalytic systems were prepared on electrochemically activated PAN-based carbon fibre supports through a procedure of repetitive cation exchange between the acidic (-OOOH and-OH) groups of the electrooxidized carbon surface and noble metal salts and subsequent cathodic reduction of the exchanged noble metal ions to the metallic state.The whole investigation was carried out for the binary system Ag-Pd. The catalytic efficiency of palladium deposited on silver is more pronounced compared to a Pd-deposition obtained after only one Pd²⁺-exchange procedure and subsequent cathodic reduction, whereas an inhibition of the catalytic activity of palladium is noticed when it is covered by silver deposition. The catalytic efficiency of the obtained mixed noble metal catalysts was studied by means of hydrogen-adsorption and absorption profiles in H₂SO₄, the electroreduction of nitrobenzene in aqueous methanolic H₂SO₄ solutions and the hydrogenation reaction of nitrobenzene to aniline in methanolic solutions. The study was completed by impedance spectroscopic measurements at the potential of hydrogen evolution in H₂SO₄ solutions.Mixed Ag-Pd systems are even more stable than double Pd-Pd depositions on activated carbon fibre supports, as shown by the fact that they retain their mechanical stability and catalytic activity even after prolonged storage in aqueous or methanolic solutions, as well as after ultrasonic treatment.     

Optimal Influence Strategies in Social Networks

This paper suggests a modeling framework to investigate the optimal strategy followed by a monopolistic firm aiming to manipulate the process of opinion formation in a social network. The monopolist and a set of consumers communicate to form their beliefs about the underlying product quality. Since the firm’s associated optimization problem can be analytically solved only under specific assumptions, we rely on the sequential quadratic programming computational approach to characterize the equilibrium. When consumers’ initial beliefs are uniform, the firm’s optimal influence strategy always involves targeting the most influential consumer. For the case of non-uniform initial beliefs, the monopolist might target the less influential consumer if the latter’s initial opinion is low enough. The probability of investing more in the consumer with the lower influence increases with the distance between consumers’ initial beliefs and with the degree of trust attributed on consumers by the firm. The firm’s profit is minimized when consumers’ influences become equal, implying that the firm benefits from the presence of consumers with divergent strategic locations in the network. In the absence of a binding constraint on total investment, the monopolist’s incentives to manipulate the network decrease with consumers’ initial beliefs and might either increase or decrease with the trust put in consumers’ opinion by the firm. Finally, the firm’s strategic motivation to communicate persistently high beliefs during the opinion formation process is positively associated with the market size, with the available budget and with the direct influence of the most influential consumer on the other but negatively associated with consumers’ initial valuation of the good.     

Electrocatalytic reactions on carbon fibre electrodes modified by hemine I. Electroreduction of oxygen

The electrocatalytic reduction of oxygen on pristine and on electro-oxidized carbon fibre electrodes modified by hemine is investigated in aqueous, methanolic and acetonitrile solutions.

The attached iron porphyrin on the modified electrodes exists in two forms, monomeric and dimeric, the latter consisting of two Fe(III)-protoporphyrin molecules held together with an oxygen atom. The catalytic activity of the electrodes is attributed to the hemine monomers, which have the ability to bond the O₂ molecule at the axial position of the metal ion of the porphyrin.

The catalytic reduction of O₂ in acidic aqueous and methanolic solutions produces H₂O, whereas in acetonitrile H₂O₂ is formed.

The electro-oxidized modified electrodes show a catalytic efficiency four-times greater than the pristine electrodes, which is consistent with the analogous increase of the effective electrode area after the electro-oxidation procedure.     

Chemical modification of electrochemically oxidized and partially rereduced carbon fibre electrodes

Carbon fibre electrodes (residual graphite oxide fibres) electrochemically oxidized and partially rereduced in concentrated H₂SO₄ have excellent cation-exchanging properties. Chemically modified carbon fibre electrodes have been prepared by Na⁺-exchange of residual graphite oxide fibres and subsequent action of chlorocompounds in methanolic solutions (the Williamson reaction).The attachment of the various reagents on to the carbon fibres is reflected through the corresponding cyclic voltammograms obtained in aqueous buffer solutions. When modified with iron phthalocyanine, carbon fibre electrodes show a significant catalytic effect on the electrochemical reduction of oxygen in aqueous and methanolic solutions.     

Electrochemical applications of graphite intercalation compounds

Real and potential applications of graphite intercalation compounds in electrochemical processes are critically surveyed. Special attention is given to the fields of “batteries” and “chemically modified carbon electrodes”.Some recent results concerning both the discharge mechanism of graphite oxide positives in organic electrolyte-lithium batteries, and the preparation of metal-doped carbon electrodes via graphite compounds with ion exchange behaviour, are presented in detail.     

Exploration of domestic water demand attitudes using qualitative and quantitative social research methods

The sustainable evolution of the urban water system requires the recognition of uncertainty embedded in both climate and human behaviour. A challenge that water managers and policy makers need to tackle, is to understand the way the society’s water demand behaviour is affected. The inaccuracy between attitudes and behaviours and the cognitive association of water use to living standards, hinders the projection of society’s response to management’s measures. Thus, it is necessary to identify leverage points, where water demand management policies should aim their efforts. This work presents two parts of a social research held in Athens: quantitative questionnaire gathering information regarding the domestic water demand attitudes and behaviours; and a series of qualitative interviews aimed at exploring in-depth, the domestic water use attitudes, and behaviours. This work presents the design and results of both methods and the combination of the quantitative results with insights from the qualitative work.     

Modeling and querying provenance by extending CIDOC CRM

This paper elaborates on the problem of modeling provenance for both physical and digital objects. In particular it discusses provenance according to OAIS (ISO 14721:2003) and how it relates with the conceptualization of CIDOC CRM ontology (ISO 21127:2006). Subsequently it introduces an extension of the CIDOC CRM ontology, able to capture the modeling and the query requirements regarding the provenance of digital objects. Over this extension the paper provides a number of indicative examples of modeling provenance in various domains. Subsequently, it introduces a number of indicative provenance query templates, and finally it describes an implementation using Semantic Web technologies.     

Integrated evaluation of radiative heating systems for residential buildings

Based on the need to reduce CO₂ emissions and minimize energy dependency, the EU Member States have set ambitious energy policies goals and have developed respective, specific regulations, in order to improve the energy performance of the building sector. Thus, specific measures regarding the buildings’ envelope, the use of efficient HVAC technologies and the integration of renewable energy systems are being constantly studied and promoted. The effective combination of these three main aspects will consequently result in maximum energy efficiency. Germany has played a key role in this development, with intensive work focusing in the improvement of the energy behaviour of the residential building stock. In this paper, the use of radiative heating systems placing special emphasis on infrared is being studied as part of the energy renovation of residential buildings from the 1970’s. This is done by applying an integrated assessment model to evaluate specific interventions regarding the improvement of the energy behaviour of the buildings’ envelope and the use of radiative heating systems, based on a thorough Life Cycle Analysis according to criteria of energy, economic and environmental performance, as well as thermal comfort.     

Postnatal Protein Intake as a Determinant of Skeletal Muscle Structure and Function in Mice—A Pilot Study

Sarcopenia is characterised by an age-related decrease in the number of muscle fibres and additional weakening of the remaining fibres, resulting in a reduction in muscle mass and function. Many studies associate poor maternal nutrition during gestation and/or lactation with altered skeletal muscle homeostasis in the offspring and the development of sarcopenia. The aim of this study was to determine whether the musculoskeletal physiology in offspring born to mouse dams fed a low-protein diet during pregnancy was altered and whether any physiological changes could be modulated by the nutritional protein content in early postnatal stages. Thy1-YFP female mice were fed ad libitum on either a normal (20%) or a low-protein (5%) diet. Newborn pups were cross-fostered to different lactating dams (maintained on a 20% or 5% diet) to generate three groups analysed at weaning (21 days): Normal-to-Normal (NN), Normal-to-Low (NL) and Low-to-Normal (LN). Further offspring were maintained ad libitum on the same diet as during lactation until 12 weeks of age, creating another three groups (NNN, NLL, LNN). Mice on a low protein diet postnatally (NL, NLL) exhibited a significant reduction in body and muscle weight persisting up to 12 weeks, unlike mice on a low protein diet only prenatally (LN, LNN). Muscle fibre size was reduced in mice from the NL but not LN group, showing recovery at 12 weeks of age. Muscle force was reduced in NLL mice, concomitant with changes in the NMJ site and changes in atrophy-related and myosin genes. In addition, μCT scans of mouse tibiae at 12 weeks of age revealed changes in bone mass and morphology, resulting in a higher bone mass in the NLL group than the control NNN group. Finally, changes in the expression of miR-133 in the muscle of NLL mice suggest a regulatory role for this microRNA in muscle development in response to postnatal diet changes. Overall, this data shows that a low maternal protein diet and early postnatal life low-protein intake in mice can impact skeletal muscle physiology and function in early life while postnatal low protein diet favours bone integrity in adulthood.