Study of shrinkage porosity in spheroidal graphite cast iron

This study aims at identifying the relationship between the shrinkage cavities and the solidification structure in spheroidal graphite cast iron. Cast samples specially designed to contain shrinkage cavities were used. The solidification macrostructure was revealed using the Direct Austempering After Solidification method, while the solidification microstructure was revealed by using colour etching. At the midsection of the pieces, the shrinkage cavities and the solidification structure were observed jointly. The study showed that the classification of shrinkage porosity found in literature does not correspond to the ductile iron solidification model recognized by most of the scientific community. Early solidification models, and therefore shrinkage formation mechanisms, were proposed in instances when there was not a thorough knowledge of the morphology of the solid phases during solidification. Nowadays, defects formation mechanisms can be described with higher accuracy. Therefore, an updated classification of shrinkage porosity for spheroidal graphite iron is proposed.     

Antimicrobial and antibiofilm activities of procyanidins extracted from laurel wood against a selection of foodborne microorganisms

This study aimed to evaluate the antimicrobial and antibiofilm activities of two procyanidins isolated from an ethyl acetate extract of laurel wood against a selection of foodborne pathogens. The analysis of the extract by HPLC–DAD/ESI–MS allowed us to detect the presence of two procyanidins, which were selectively isolated and identified by chromatographic and spectroscopic means as cinnamtannin B‐1 ( 1 ) and procyanidin B‐2 ( 2 ). Procyanidins 1 and 2 exhibited two biological activities: inhibition of bacterial growth at high concentrations and prevention of biofilm formation at lower concentrations. Synergistic effect was also detected when both compounds were tested in combination against Listeria monocytogenes. Significant effects were also detected on disruption of preformed biofilm. The ability of procyanidins to inhibit microbial growth and biofilm formation and to synergistically work with each other may stimulate a market as natural food preservatives, and/or natural sanitisers for processing equipment where foodborne pathogens reside.     

Comparative study of chelating ion exchange resins for the recovery of nickel and cobalt from laterite leach tailings

Commercially available chelating resins with the iminodiacetate functional group have been evaluated for their suitability for the adsorption of nickel and other metal ions by a resin-in-pulp process from the tailings of a pressure acid leach process for nickel laterites. The Amberlite IRC 748 and TP 207 MonoPlus resins were found to be the most suitable in terms of loading capacity for nickel and kinetics of adsorption. The resin with the highest nominal capacity was observed to adsorb less nickel as a result of the adsorption of greater amounts of the impurity ions. The equilibrium loading for nickel on the preferred resin was found to be similar from the ammonium and protonated form of the resin although the kinetics of adsorption is greater when the resin is initially in the ammonium form. A study of the kinetics of the loading of nickel and cobalt from pulp has shown that the rate can be described in terms of a first-order approach to equilibrium. The optimum pH for adsorption was found to be in the range 4 to 5 as this pH is high enough to maximize the adsorption of nickel and cobalt while preventing precipitation of nickel and cobalt as hydroxides from the pulp. A method for minimizing the competition from more strongly loaded ions such as iron(III) and chromium(III) which are present in the pulp was also developed in the initial laboratory phase of the study.     

A voltage controlled CMOS current divider with linear characteristic

A compact voltage controlled CMOS current divider is presented. Differently from previous implementations, exploiting the MOSFET translinear characteristics in subthreshold region, the proposed circuit is based on devices operating from moderate to strong inversion. An input current linearity range of nearly a decade is obtained by compensating for the deviations from the ideal drain current square-law approximation through an original empirical approach. The circuit is suitable for use as a building block in analog multipliers and for transconductor continuous tuning. The effectiveness of the proposed configuration is demonstrated by means of electrical simulations, performed on a prototype designed with a commercial process. The robustness of the linearization algorithm with respect to temperature variations is proven.     

A New Approach to Calculate the Mud Density for Wellbore Stability Using the Asymptotic Homogenization Theory

Abstract

This study addresses mud density prediction as part of wellbore stability analyses considering effective rock properties and using friction and elastic theories to determine the deviator stress at failure. The effective rock properties for different sandstone porosities were obtained through the theory of asymptotic homogenization, and the wall vicinity stresses at the borehole wall were estimated considering friction and elastic theories. The use of the method of asymptotic homogenization (MHA) allows obtaining effective rock mechanical properties varying in porosity and saturation conditions.     

Convergent optical correlator aligment based on frequency filtering

The convergent correlator is widely used but it presents the drawback of the alignment requirements: fine focusing of the input scene Fourier transform on the filter plane, filter centering, scaling the scene Fourier transform to match the filter size, and azimuth matching of the filter with the input scene. We propose a set of tests to obtain a precise alignment of the convergent correlator. These methods are based on frequency filtering properties and they are applicable either for amplitude input or for phase-encoded input. The tests we present allow us to fulfill all the alignment requirements. The theory on which these tests are based is explained. The experimental results obtained during the alignment procedure are presented. We show some additional verifications of the correct alignment of the convergent correlator.     

Requirements Reuse for Improving Information Systems Security: A Practitioner’s Approach

Information systems security issues have usually been considered only after the system has been developed completely, and rarely during its design, coding, testing or deployment. However, the advisability of considering security from the very beginning of the system development has recently begun to be appreciated, and in particular in the system requirements specification phase. We present a practical method to elicit and specify the system and software requirements, including a repository containing reusable requirements, a spiral process model, and a set of requirements documents templates. In this paper, this method is focused on the security of information systems and, thus, the reusable requirements repository contains all the requirements taken from MAGERIT, the Spanish public administration risk analysis and management method, which conforms to ISO 15408, Common Criteria Framework. Any information system including these security requirements must therefore pass a risk analysis and management study performed with MAGERIT. The requirements specification templates are hierarchically structured and are based on IEEE standards. Finally, we show a case study in a system of our regional administration aimed at managing state subsidies.     

An audit of magnetic resonance imaging in the paediatric orthopaedic setting

AIMS: To determine when magnetic resonance imaging (MRI) is helpful in the management of a selected group of paediatric orthopaedic patients. METHODS: A retrospective analysis of 131 MRI scans was undertaken with allocation into seven categories based on clinical presentation. RESULTS: MRIs performed for spinal, congenital and intra-articular pathology, as well as for growth plate assessment correlated well with subsequent clinical and/or surgical findings. Three of ten MRIs (30%) incorrectly assessed whether a foreign body was present with a sensitivity of 0.60 and specificity of 0.80. Three of 20 MRIs (15%) could not accurately distinguish between oedema/effusion and frank infection. Here sensitivity was 1.00 and specificity was 0.73. MRIs performed for assessment of tumours were accurate with respect to margins and extent. Assessment of pathology with MRI was never the indication for MRI, thus it was not surprising that in four of 27 soft tissue tumours (sensitivity of 0.88 and specificity of 0.63) MRI did not correlate with subsequent histological findings. CONCLUSIONS: MRI plays an important role in the assessment of a wide range of musculo-skeletal pathology. MRI does not, and could not be expected to, replace the need for incisional biopsy for tumour diagnosis. It must be used with caution where tissues have been previously explored for foreign bodies. Interpretation of MRI in musculoskeletal infection must consider its timing in the evolution of the patient's infection.     

Separating hierarchical relations and word order in language production: is proximity concord syntactic or linear?

In this paper we address the question whether hierarchical relations and word order can be separated in sentence production. In two experiments, we assess whether subject-verb agreement errors (such as 'The time for fun and games are over') require linear proximity of a so-called 'local' noun ('games' in the example) to the verb. In the first experiment, we found a proximity effect when participants were asked to complete sentential beginnings of the kind: 'The helicopter for the flights'. In the second experiment, we asked participants to produce a question such as 'Is the helicopter for the flights safe?'. The syntactic relation between the subject noun and the local noun is the same in the two experiments, but the linear position of the local noun is different. The distribution of agreement errors was similar in the two experiments. We argue that these data provide evidence for a stage in language production in which a syntactic structure is built prior to a stage in which words are assigned to their linear position. Agreement is computed during the first stage.     

Tonic regulation of excitation-contraction coupling by basal protein kinase C activity in isolated cardiac myocytes

A high-speed imaging technique was used to investigate the effects of inhibitors and activators of protein kinase C (PKC) on the [Ca2+]i transients and contraction of fura-2 loaded rat ventricular cardiac myocytes. The amplitude of the [Ca2+]i transient was reduced following treatment with 100 nM phorbol 12,13-dibutyrate (PDBu), whereas the PKC inhibitors staurosporine (0.5 microM) and calphostin C (10 microM) increased [Ca2+]i transient amplitude, elevated basal [Ca2+]i and slowed the decay of the [Ca2+]i transient. These changes were paralleled by similar alterations in the rate and extent of cell shortening. The activity of nitrendipine-sensitive Ca2+ channels was monitored indirectly as the rate of Mn2+ quench of cytosolic fura-2 in electrically-paced cells. PDBu reduced Mn2+ influx by six-fold, whereas staurosporine and calphostin C increased the influx rate by eight-fold and seven-fold over basal quench, respectively. The caffeine releasable Ca2+ pool was reduced in the presence of PDBu and increased transiently in presence of staurosporine. The effects of PKC activation and inhibition on sarcoplasmic reticulum Ca2+ content may be secondary to alterations of sarcolemmal Ca2+ influx. However, the PKC inhibitors also decreased the rate of sarcoplasmic reticulum Ca2+ uptake in permeabilized myocytes, suggesting that a direct effect of PKC on the sarcoplasmic reticulum may contribute to the prolongation of the [Ca2+]i transient under these conditions. The present work demonstrates that basal PKC activity has a potent depressant effect, mediated primarily through inhibition of sarcolemmal Ca2+ influx, which may play a key role in setting the basal tone of cardiac muscle.