Investigation of O2 reduction in alkaline media on macrocyclic chelates impregnated on different supports: influence of the heat treatment on stability and activity

Several macrocyclic chelates impregnated on different carbon supports were investigated using a three-phase electrode. Pyrolysed CoTMPP on treated Vulcan yields comparable results to dispersed Pt. XPS investigations reveal, for the most stable compounds, either a special bond with carbon (CoTMPP) or in some cases nitride formation (MoNPc). With the most active compounds, the MeN₄ unit is preserved after heat treatment. The affinity of carbon or nitrogen with the metal compared to the O₂ affinity is essential.     

Designing with scenarios: A critical review of current research and practice

There is a great deal of requirements engineering specifically, and information systems development research in general, in the area of scenarios as the ‘vocabulary’ for discussing and characterising designs for new artefacts. This is partly due to opening up the design process to a variety of participants in a project, and making explicit their ways of working, thinking and interactions with the design products. Scenarios, being concrete, and easy to understand and use, provide the means to describe the design vocabulary. They are used to focus on episodic cases, exchange ideas and thoughts about them effectively, and generally describe requirements and designs for a new artefact from the user’s perspective. In this paper, we review the effectiveness of the current state-of-practice in scenario-based approaches. The objective of this evaluation exercise is to define the requirements for improved ‘by scenario’ approaches to cope with requirements and designs for developing new artefacts.     

Detailed multitechnique spectroscopic surface and bulk characterization of plasma polymers deposited from 1-propanol,allyl alcohol,and propargyl alcohol

Three monomers with different degrees of unsaturation, 1-propanol, allyl alcohol, and propargyl alcohol, are plasma-deposited to obtain alcohol functions containing polymers. To obtain information on the behaviors of these monomers in the plasma, the polymers deposited in the reactor and in the postdischarge region are characterized by high-energy resolution XPS, IR, HREELS, elemental analysis, and chemical derivatization. XPS results show that oxygen-rich polymers can be obtained from the unsaturated monomers at low power for both regions or at high power in the postdischarge region. In the reactor at high power, fragmentation of the monomer leads to the elimination of oxygen fragments and ablation reactions during the polymerization process. Detailed structural information on the chemical structure and content of functional groups are obtained by simulation of the XPS C1s core levels of the polymers before and after derivatization with trifluoroacetic anhydride. In soft conditions, allyl alcohol leads to the formation of polymers with a relatively low degree of crosslinking and a high hydroxyl content (53–72%). However, the high resolution of the XPS spectrometer allows one to detect the presence of secondary or tertiary alcohol functions resulting from chain branching reactions in this polymer. Results from this multitechnique characterization indicate also that the hydroxyl conversion and crosslinking reactions are more pronounced for poly(1-propanol) and poly(propargyl alcohol). Alcohol, ether, and carbonyl functions are present in equivalent quantities in poly(propargyl alcohol) while poly(1-propanol) contains mainly ether functions (50%). The presence or absence of alcohol functions at the extreme surface of the polymers in relation to the chain mobility and the tendency of hydrogen bonding between hydroxyl groups was studied by HREELS. © 1996 John Wiley & Sons, Inc.     

Volatile organic compounds of mountainous plant species and the produced milk as affected by altitude in Greece: A preliminary study

The objective of this study was to characterise the volatile organic compounds (VOCs) profile of plant species, bulk forage grazed by sheep and produced milk at different mountainous areas of Greece. The most abundant plant species of vegetation at 800 m (hill‐land) and 1300 m (highland) altitude, bulk forage and milk samples, were collected. The VOCs profiles of the plant species and milk varied. Common VOCs in milk from both areas were identified, whereas others were discriminatory for each area. Overall, the VOCs composition of mountainous milk could provide a basis for Feta cheese identification with its region.     

Quality control and storage studies of virgin olive oil: Exploiting UV spectrophotometry potential

The present work was undertaken in order to examine whether K₂₃₂ values and other UV absorbance characteristics could replace the determination of peroxide value (PV) in routine quality control and also in storage studies of virgin olive oil (VOO). For this reason, PV and extinction coefficients were determined for a large number of VOO samples (n = 40). The samples were then stored at 45 °C for several weeks. Changes in the lipid matrices were monitored by periodic measurements of the same quality indices. UV absorption spectra and the respective derivative ones were obtained before and during storage. Regression data showed that the PV is correlated with the K₂₃₂ value not only at time zero but also during storage. Evidence derived from the first derivative spectrum is strongly related to the oxidative status of the oil. The findings may be used (a) to simplify the decision tree suggested for “the verification of consistency of a VOO sample with commercial category declared” in the EEC Regulation N^o 1989 (2003), which takes into account acidity measurement, PV and absorbance values (K₂₇₀, ΔK, K₂₃₂), and (b) to collect qualitative and quantitative information about the oxidation process during storage.     

Comparison between laser‐induced nucleation of ZnS and CdS nanocrystals directly into polymer matrices

The nucleation of two kinds of crystalline nanoparticles, zinc sulfide (ZnS), and cadmium sulfide (CdS), is achieved directly into specific sites of polymer matrices after their irradiation with UV laser pulses. The starting samples consist of polymers doped with precursors of Zn or Cd thiolate that are proved to decompose after the absorption of UV light, resulting into the nanoparticles formation. The growth of the crystalline nanostructures is followed throughout the irradiation of the samples with successive incident pulses, by different methods, such as transmission electron microscopy, atomic force microscopy, confocal microscopy, and X‐ray diffraction. Special attention is paid to the difference of the formation pathways of the two kinds of nanoparticles studied, because the Cd thiolate precursor exhibits much higher absorption efficiency than the Zn thiolate one, at the applied UV wavelength. Indeed, CdS nanoparticles become evident after the very first incident UV pulses, whereas the formation of ZnS nanocrystals requires rather prolonged irradiation, always through a macroscopically nondestructive procedure for the polymer matrix. POLYM. COMPOS., 2010. © 2009 Society of Plastics Engineers     

Localized formation and size tuning of CdS nanocrystals upon irradiation of metal precursors embedded in polymer matrices

We present a method of spatial and dimensional controlled formation of CdS quantum dots into polymer matrices by light irradiation. The initial samples consist of Cd thiolate precursors doped in TOPAS polymer matrix. Under pulsed UV laser irradiation the precursors are photolysed driving to the nucleation of CdS nanocrystals, with increasing size and concentration, related to the number of UV pulses. The formed quantum dots are localized in the irradiated area, while the host polymer remains macroscopically unaffected by the UV irradiation. In this study we investigate how the formation of the nanocrystals (size, dimensions, and concentration) is affected by the use of different irradiation conditions (wavelength, number of pulses), revealing information about the different pathways followed during the formation. The change of the size of the dots results in the change of the peak of their emission due to the quantum size effect, which is studied by fluorescence measurements. The results are reinforced by TEM microscopy and by XRD measurements. The main advantages of the presented method are the size tuning of the produced dots and their spatial confinement inside the host matrix, not possible by the other methods used until now (thermal annealing, mixing etc.).     

The Effects of Fatigue on the Atomic Structure with Cyclic Loading in Zr50Cu40Al10 and Zr60Cu30Al10 Glasses

The potential damage effect from fatigue on Zr bulk metallic glass alloys of Zr₅₀Cu₄₀Al₁₀ at the eutectic point and Zr₆₀Cu₃₀Al₁₀ away from the eutectic point (in atomic percent) is examined via the local atomic structure, which was obtained from the pair density function analysis of the synchrotron X-ray radiation and neutron data. Samples cut from the same rods were subjected to 10⁴, 10⁵, and 10⁶ compression cycles ex situ, and the evidence for fatigue damage was investigated by comparing alloys before and after cyclic loading. Bond orientation was observed particularly in Zr₅₀Cu₄₀Al₁₀, suggesting that fatigue damage occurs even in the elastic range, below the yield point, and during cyclic loading. The initiation of fatigue changes is observed first within small localized atomic regions.