Catalytic wet oxidation of phenol over lanthanum strontium manganite

The catalytic performances of lanthanum strontium manganite (La_0.8Sr_0.2)Mn_0.98O₃, in catalytic wet oxidation (CWO) of a phenol solution under milder conditions of temperature (398–498 K) and pressure (P_o2=4 bar), in a batch reactor, have been investigated. Aim of this study is the evaluation of the effect of temperature, catalyst loading, phenol concentration and stirrer speed on phenol conversion. Experimental data obtained from the different test conditions are best-fitted to evaluate the effective reaction order and apparent activation energy.     

Measures to reduce pesticide spray drift in a small aquatic ecosystem in vineyard estate

A field experiment is reported to ascertain the drift of two pesticides (chlorpyrifos and metalaxyl) in a vineyard in Italian climatic conditions and the effect of mitigation measures, such as buffer zones and tree rows, on pesticide drift contamination in a small aquatic system located inside the field. Results indicated that, in typical Italian agricultural conditions, spray drift in vineyards occurs at a distance of more than 24 m and adequate buffer zones are required to protect surface water bodies from direct contamination. The presence of tree rows in front of the water body inside the agricultural field, against the main wind direction, resulted in a very high reduction of the spray drift and of the ecotoxicological risk for aquatic ecosystem. In addition, a comparison between the data obtained in the experiment and the Drift Calculator procedure showed that the model failed when the procedure is used for short distances. However, concordance was found in terms of maximum drift distances.     

Layer-by-Layer Self-Assembled Redox Polyelectrolytes on Passive Steel

Steel samples were passivated in 0.1 M NaOH solutions at 0.3 V vs. Ag/AgCl (3 M KCl) and then poly(allylamine) derivatized with osmium pyridine-bipyridine-chloride complex and poly-(vinylsulfonate) were sequentially self-assembled electrostatically layer-by-layer. The resulting electrodes were examined by cyclic voltammetry, ellipsometry, and X-ray Photoelectron Spectroscopy (XPS). These studies demonstrate the formation of a redox polyelectrolyte multilayer onto the passive film protecting the ferrous metal. As the number of deposited polyelectrolyte layers increases there is an increase in the measured thickness of the self-assembled film. The rate of thickness growth in osmium polymer film with the number of deposition cycles is slower for films thinner than ∼30 nm. Cyclic voltammetry shows that the electron transfer rate to the outer sphere osmium complex tethered to the polymer backbone is much slower for the multilayer on passive iron than on gold surfaces. This is in agreement with the well-known behavior of soluble redox couples on passive metals and with electrochemical tunelling spectroscopy.     

A stochastic approach for the water demand of residential end users

Reliable hydraulic modeling of water distribution networks requires a deep knowledge of water demand. In the past few years, technical literature has been enriched with many contributions aimed at realistically representing the residential water demand of end users. The proposed models generally represent water demand through rectangular pulses, describing demand as the sum of the requests from single domestic appliances. This paper proposes a new stochastic model - Overall Pulse (OP) - which allows the generation of the overall domestic demand as displayed at the house water meter. The proposed model allows the taking into account of the randomness of the arrivals rate and the demand persistence phenomenon. The effectiveness of the proposed model has been tested, comparing the generated data series with those measured for residences with different lifestyles. The generation of the synthetic data series has been made by means of the OP model with the Monte Carlo method.     

Controlled navigation of endoscopic capsules: concept and preliminary experimental investigations

This paper describes a technique to control the navigation of traditional wireless endoscopic capsules and reports preliminary proof-of-concept investigations. These capsules are used for noninvasive explorations of the digestive tube. At present, their motion cannot be controlled and they proceed by means of the visceral peristalsis. In order to enable motion controls, the technique proposed here adopts magnetic shells which are to be applied to available capsules, immediately before their use. The shells are used to control the capsule movement by means of external magnetic fields. This solution is readily applicable to any endoscopic capsule, avoiding internal modifications. Prototype elastic shells made of silicone elastomers mixed with magnetic particles were fabricated. They were tested with the most diffused capsule (model M2A, Given Imaging Ltd., Yoqneam, Israel), by studying the performance of the capsule/shell complex in simplified experimental conditions. Bench tests permitted to demonstrate controlled translations, rotations, and rototranslations of the capsule/shell complex within tubular structures coated with pieces of bovine tissues. The use of a new instrumentation, recently developed for cardiovascular treatments, is proposed as a potential means enabling the application of controlled magnetic fields for intrabody navigations.     

Quadrant kinoform: an approach to multiplane dynamic three-dimensional holographic trapping

Real-time dynamic holographic optical tweezers suffer from an intrinsic limitation. The diffractive optical element, which is the key to reconstruction, requires time for the calculation and physical constraints to be satisfied. In particular, when working in a volume these requirements become highly expensive. Quadrant kinoform represents an alternative to traditional 3D holograms. A spatial domain multiplexing combined with lens term phase profiles allow the independent addressing and control of different planes in the reconstruction volume. The bidimensional holograms used pose less severe physical constraints and the reduced size leads, at the cost of a lower reconstruction resolution, to a consistent speedup in the computation time thus improving real-time interactions.     

The microstructure and mechanical properties of Fe–Cu materials fabricated by pressure-less-shaping of nanocrystalline powders

The microstructure of Fe-40%_wtCu nanocrystalline powders, prepared by mechanical alloying, was studied before and after the consolidation process. Pressure-less-shaping (PS) was used to consolidate the powders. The PS technique, similar to metal injection moulding (MIM), does not require external pressure in order to fill up the mould. The key factor of the process of consolidation is the use as binder a hybrid inorganic–organic monomer, formed by the reaction of zirconium propoxide and 2-hydroxy ethyl methacrylate. This type of monomer, mixed with the metallic powders, formed slurry having low viscosity, which was easily poured into mould. The binder stiffened upon polymerization. Some pieces were produced through debinding and sintering, both performed under inert atmosphere in order to avoid metal oxidation. Different microstructure and density were observed depending on the maximum sintering temperatures, ranging from 904 to 1,120 °C. In the sample sintered at 1,120 °C, the crystalline domains of the copper phase were of about 40 nm.     

A two-colour heterojunction unipolar nanowire light-emitting diode by tunnel injection

We present a systematic study of the current-voltage characteristics and electroluminescence of gallium nitride (GaN) nanowire on silicon (Si) substrate heterostructures where both semiconductors are n-type. A novel feature of this device is that by reversing the polarity of the applied voltage the luminescence can be selectively obtained from either the nanowire or the substrate. For one polarity of the applied voltage, ultraviolet (and visible) light is generated in the GaN nanowire, while for the opposite polarity infrared light is emitted from the Si substrate. We propose a model, which explains the key features of the data, based on electron tunnelling from the valence band of one semiconductor into the conduction band of the other semiconductor. For example, for one polarity of the applied voltage, given a sufficient potential energy difference between the two semiconductors, electrons can tunnel from the valence band of GaN into the Si conduction band. This process results in the creation of holes in GaN, which can recombine with conduction band electrons generating GaN band-to-band luminescence. A similar process applies under the opposite polarity for Si light emission. This device structure affords an additional experimental handle to the study of electroluminescence in single nanowires and, furthermore, could be used as a novel approach to two-colour light-emitting devices.