Determination of water content in Brazilian honeybee-collected pollen by Karl Fischer titration

This paper assesses the performance of a chemical method based on the Karl Fischer titration to determine the water content in samples of dehydrated honeybee-collected pollen. The following analysis parameters were investigated: extraction temperature, particle size, reaction time, and weight of a dried pollen sample. After optimization, the method was used to determine the water content of 154 samples of dried honeybee-collected pollen from different geographical regions of Brazil. The Karl Fischer titration method, performed using a solvent mixture of methanol and n-octanol (1:1 v/v) at 50 °C on pollen particles 600 μm in size produced the best results. Mean values for water content of the 154 samples of dried honeybee-collected pollen from 12 Brazilian regions ranged from 3% to 9%.     

Fracture resistance of a doped PZT ceramic for multilayer piezoelectric actuators: Effect of mechanical load and temperature

The fracture resistance behaviour of a doped lead zirconate titanate (PZT) ceramic after combined thermo-mechanical loading is investigated between room temperature (RT) and 400 °C, i.e. above the Curie temperature (T_C). The thermal- and stress-induced depolarisation effects due to domain switching have been assessed by the indentation method on bulk PZTs. This has been extended to multilayered actuators. Experimental findings show a depolarisation effect with the temperature, which is significantly enhanced when combined with mechanical loading. This partial or even full depolarisation of the PZT material below T_C leads to important anisotropy effects in the fracture resistance of the piezo-ceramic, which should be taking into account in the design of multilayer actuators where the direction of crack propagation (i.e. parallel or normal to electrodes) can affect the actuator functionality.     

Polyaniline coatings on aluminium alloy 6061-T6: Electrosynthesis and characterization

The production of polyaniline films on aluminium alloy 6061-T6 in sulphuric acid was carried out by electrodeposition, using cyclic voltammetry and potentiostatic polarization. The films obtained were characterized by SEM and XPS analysis. Electrochemical techniques were also used to assess the anticorrosive properties of the coatings.The choice of the upper potential limits for potential cycling and of the fixed potential for potentiostatic production should take in consideration the balance between their effect on the minimum number of cycles (or time) needed to produce the film and on the rate of overoxidation.Polarization curves show a slight increase of the corrosion potential for polyaniline coated substrate as compared with bare metal, indicating that no significant protection is achieved by the polymer coating. The Bode diagrams show low impedance values for the alloy covered with polyaniline when compared with the results obtained for the bare metal. This can be attributed to the conductive character of the polyaniline films.     

The antioxidant activity of teas measured by the FRAP method adapted to the FIA system: Optimising the conditions using the response surface methodology

This study proposes a FRAP assay adapted to FIA system with a merging zones configuration. The FIA system conditions were optimised with the response surface methodology using the central composite rotatable design. The optimisation parameters studied were: the carrier flow rate, the lengths of the sample and reagent loops, and reactor length. The conditions selected in accordance with the results were: carrier flow rate of 1.00 ml/min, length of the loops 18.2 cm and length of the reaction coil 210.1 cm. The detection and quantification limits were, respectively, 28.6 and 86.8 μmol/l Fe²⁺, and the precision was 1.27%. The proposed method had an analytical frequency of 30 samples/h and about 95% less volume of FRAP reagent was consumed. The FRAP assay adapted to the FIA system under the optimised conditions was utilised to determine the antioxidant activity of tea samples.     

Ground Movements around Corners of Excavations: Empirical Calculation Method

This paper presents an empirical methodology that allows calculation of ground displacements behind corners of retained cut excavations. The increased stiffness of a retaining wall at the corner of an excavation normally leads to a corresponding reduction in ground movements behind the retaining wall. These “corner effects” derived from retained cut excavations can only be assessed at present by using three-dimensional numerical analysis or empirical methods. Significant cost and time can be taken carrying out three dimensional analysis, which, additionally, is not normally carried out at an early stage of the design of a project. Furthermore, numerical analysis must be undertaken by a competent person with appropriate training. An inappropriate analysis can yield to misleading and counterproductive results. This constitutes an expensive requirement on practitioners that often resort to more conservative designs which ignore corner effects. The methodology of adjusting calculated ground movements around corners of excavations described in this paper is simple to use and easy to program into software or spreadsheets. It can be used in conjunction with two-dimensional numerical analysis and also for calculating displacements in early stages of projects when numerical analysis has not yet been undertaken. This allows for more informed early discussion with third parties where approvals are sought on a given project.     

A Perturbation Expansion Method to Study Highly Correlated Spins

This paper proposes a new numerical algorithm to study dynamical spin dependent properties of local highly correlated structures. The method consists in diagonalizing a finite cluster containing the many-body terms of the Hamiltonian and embedding it into the rest of the system, the Embedding Cluster Approximation (ECA), combined with Wilson’s ideas of logarithmic discretization of the representation of the Hamiltonian, the Logarithm Discretization Embedded Cluster Approximation (LDECA). The physics associated to a dot and a side-coupled double dot connected to leads are discussed in detail.     

Effect of uranium (VI) on two sulphate-reducing bacteria cultures from a uranium mine site

This work was conducted to assess the impact of uranium (VI) on sulphate-reducing bacteria (SRB) communities obtained from environmental samples collected on the Portuguese uranium mining area of Urgeiriça. Culture U was obtained from a sediment, while culture W was obtained from sludge from the wetland of that mine. Temperature gradient gel electrophoresis (TGGE) was used to monitor community changes under uranium stress conditions. TGGE profiles of dsrB gene fragment demonstrated that the initial cultures were composed of SRB species affiliated with Desulfovibrio desulfuricans, Desulfovibrio vulgaris and Desulfomicrobium spp. (sample U), and by species related to D. desulfuricans (sample W). A drastic change in SRB communities was observed as a result of uranium (VI) exposure. Surprisingly, SRB were not detected in the uranium removal communities. Such findings emphasize the need of monitoring the dominant populations during bio-removal studies. TGGE and phylogenetic analysis of the 16S rRNA gene fragment revealed that the uranium removal consortia are composed by strains affiliated to Clostridium genus, Caulobacteraceae and Rhodocyclaceae families. Therefore, these communities can be attractive candidates for environmental biotechnological applications associated to uranium removal.     

ITER Upper Port Plug handling cask system assessment and design proposals

The current design of the ITER cask for Upper Port Plugs has been evaluated. Careful reduction of the number of mechanical degrees of freedom is an opportunity to relax the tolerances in the design, resulting in cost reduction and reliability increase. A new kinematical design for the tractor module has a higher stiffness to weight ratio, reduces actuator forces by a factor four and minimizes cross-talk between lift and rotation motion. Non-cantilevered handling is recommended to reduce wheel loads on the tractor by a factor six and to simplify guidance. At the system level the tubular guide (TG) is proposed, a semi-permanent 3.5 m long tube which is an extension of the Upper Port. Cask docking is simplified and the risk of the cask tilting is prevented. Redesigning the system concept is recommended and the TG looks promising. Since a system level redesign impacts the external interfaces, overall feasibility has to be investigated.     

Bayesian recursive estimation of linear dynamic system states from measurement information

The evaluation of uncertainty in dynamic measurements has recently become a demanding issue. A Bayesian approach is employed here to derive the equations required to recursively generate the solution to the problem of estimating (and predicting) the states of linear dynamic systems. It is shown that this approach allows a derivation of Kalman’s filtering algorithm which is more easily accessible to those involved with dynamic measurements. The complete time-varying Kalman filter is particularly useful when the linear dynamic system and/or signal statistics are time varying and also when optimum estimates are required from the very beginning.