Development and validation of a high-performance liquid chromatography-mass spectrometry assay for determination of amphetamine, methamphetamine, and methylenedioxy derivatives in meconium

A procedure based on liquid chromatography-mass spectrometry (LC-MS) is described for determination of amphetamine, methamphetamine, and methylendioxy derivatives in meconium, using 3,4-methylendioxypropylamphetamine as internal standard. The analytes were initially extracted from the matrix by 17 mM methanolic HCl. Subsequently, a solid-phase extraction with Bondelut Certify columns was applied. Chromatography was performed on a C(18) reversed-phase column using a linear gradient of 10 mM ammonium bicarbonate, pH 9.0-methanol as a mobile phase. Analytes were determined in LC-MS single ion monitoring mode with an atmospheric pressure ionization-electrospray interface. The method was validated in the range 0.005-1.00 microg/g using 1 g of meconium per assay. Mean recoveries ranged between 61.1 and 87.2% for different analytes. The quantification limits were 0.005 microg/g meconium for amphetamine, methamphetamine, and 4-hydroxy-3-methoxymethamphetamine and 0.004 microg/g meconium for 3,4-methylenedioxyamphetamine, 3,4-methylenedioxymethamphetamine, 3,4-methylenedioxyethylamphetamine, and N-methyl-1-(3,4-methylenedioxyphenyl)-2-butanamine. The method was applied to analysis of meconium in newborns to assess eventual fetal exposure to amphetamine derivatives.     

Sliding mode control based buck-boost bidirectional converter to drive piezoelectric loads

The present work deals with the development of a converter to drive piezoelectric actuators to be used in automotive and aerospace applications and work under mechanical frequencies up to 2 kHz with rectangular, triangular and sinusoidal reference signals. In order to maximize the field in the piezoelectric ceramic important voltages (up to 2,000 V) are needed. To fulfill such requirements with a limited input voltage a bidirectional buck-boost converter is proposed. Such a converter shows voltage reduction and elevation capability. This advantage overcomes its intrinsic control non-linearity and the drawbacks involved. The converter is controlled by means of a sliding mode control strategy based on two different linked sliding surfaces which are defined as the energy error of the converter for charging and discharging operation modes, so that each surface controls one of the two switches employed. The state-space evolution of the voltage and current is investigated in order to analyze the converter limitations. The proposed converter and control strategy have been simulated and have proved to be appropriate and robust for different voltage references and values of the equivalent capacitance C _P .     

ATMOSPHERIC FREEZE-DRYING PART 1 : DESIGN,EXPERIMENTAL INVESTIGATION AND ENERGY-SAVING ADVANTAGES

This paper describes the experimental study of a new process for freeze-drying based on a fluidized bed of dry adsorbent working at atmospheric pressure. Process feasibility has been demonstrated. The kinetics of dehydration have been established systematically for thin-sliced potatoes. A comparison has been carried out with vacuum freeze-drying. Processing time is longer than under vacuum freeze-drying, but energy savings of 35% can be expected from a continuous duty facility.     

A multi-objective control strategy for grid connection of DG (distributed generation) resources

This paper presents a flexible control technique for connection of DG (distributed generation) resources to distribution networks, especially during ride-through on faulty grid. This strategy is derived from the abc/αβ and αβ/dq transformations of the ac system variables. The active and reactive currents injected by the DG source are controlled in the synchronously rotating orthogonal dq reference frame. The transformed variables are used to control the VSI (voltage source inverter) which connects the DG to the distribution network. Using a P.L.L. (phase locked loop) in circuit of proposed control technique, the angle of positive sequence has been detected, in order to synchronize the currents to the distribution network. The proposed control technique has the capability of providing active and reactive powers and harmonic currents to nonlinear loads with a fast dynamic response. Simulation results and mathematical analysis have been completed in order to achieve a reduced THD (total harmonic distortion), increased power factor and compensated load’s active and reactive powers. The analyses show the high performance of this control strategy in DG applications in comparison with other existing strategies.     

Traffic sign recognition system with β -correction

Traffic sign classification represents a classical application of multi-object recognition processing in uncontrolled adverse environments. Lack of visibility, illumination changes, and partial occlusions are just a few problems. In this paper, we introduce a novel system for multi-class classification of traffic signs based on error correcting output codes (ECOC). ECOC is based on an ensemble of binary classifiers that are trained on bi-partition of classes. We classify a wide set of traffic signs types using robust error correcting codings. Moreover, we introduce the novel β-correction decoding strategy that outperforms the state-of-the-art decoding techniques, classifying a high number of classes with great success.     

Ge extraction from gasification fly ash

Water-soluble germanium species (GeS₂, GeS and hexagonal-GeO₂) are generated during coal gasification and retained in fly ash. This fact together with the high market value of this element and the relatively high contents in the fly ashes of the Puertollano Integrated Gasification in Combined Cycle (IGCC) plant directed our research towards the development of an extraction process for this element. Major objectives of this research was to find a low cost and environmentally suitable process. Several water based extraction tests were carried out using different Puertollano IGCC fly ash samples, under different temperatures, water/fly ash ratios, and extraction times. High Ge extraction yields (up to 84%) were obtained at room temperature (25 °C) but also high proportions of other trace elements (impurities) were simultaneously extracted. Increasing the extraction temperature to 50, 90 and 150 °C, Ge extraction yields were kept at similar levels, while reducing the content of impurities, the water/fly ash ratio and extraction time. The experimental data point out the influence of chloride, calcium and sulphide dissolutions on the Ge extraction.     

Evaluation of colour difference formulae

Values obtained by using five colour difference formulae in a set of 106 pairs of textile samples are compared with visual assessments. These included not only total colour difference, but also their psychophysical components (lightness, chroma and hue differences). Visual data used for the comparisons are the average from more than eight observers' assessments, carried out under standardised conditions by means of the grey scale method. Linear regression calculations show that the new CIEDE2000 formula gives similar results to the CMC(2:1) formula, with the differences between correlation coefficients not being statistically significant. The application of performance factors helps to ascertain the superiority of these two formulae over the other three tested. This is valid not only for total colour difference, but also for its individual components.     

Digital Control of a Power Conditioner for Fuel Cell/Super-capacitor Hybrid System

This article proposes a digital control scheme to operate a proton exchange membrane fuel cell module of 1.2 kW and a super-capacitor through a DC/DC hybrid converter. A fuel cell has been proposed as a primary source of energy, and a super-capacitor has been proposed as an auxiliary source of energy. Experimental validation of the system implemented in the laboratory is provided. Several tests have been performed to verify that the system achieves excellent output voltage (V₀) regulation and super-capacitor voltage (V_SC) control under disturbances from fuel cell power (P_FC) and output power (P₀) as well as other perturbations described in analysis results.     

Inhibitory effect of melanins from Agaricus bisporus polyphenol oxidase and two different substrates on carboxypeptidases A and B activity

In recent years, some beneficial effects on health of melanins that are formed as a result of polyphenol oxidase action have been discovered. However, it is also known that similar polymers have a detrimental effect on proteases activity. Thus, the aim of this work was to assay whether melanins from two different substrates act as carboxypeptidase A and carboxypeptidase B inhibitors. It was found that melanin synthesized from l-tyrosine decreases both the apparent affinity between carboxypeptidases and their substrates and the maximum reaction rate. Consequently, it is possible to conclude that these melanins inhibit CPA and CPB activity in a mixed way. On the contrary, no inhibition was found in the case of melanin synthesized from 4-methylcatechol.