José Machado da Silva

Adaptive digital correction of analog errors in MASH ADCs. II. Correction using test-signal injection

For pt. I see ibid., vol. 47, no. 7, p. 621-8 (2000). This part describes a different adaptation strategy. It relies on the injection of a pseudorandom two-level test signal at the input of the first-stage quantizer, where it is added to the quantization noise. The test signal then leaks into the output signal, where it can be detected and used to control the digital noise-cancellation filter. This paper describes the correction process, as well as some efficient structures for implementing it, and demonstrates the effectiveness of the technique by describing three design examples.

Long lasting perfume--a review of synthetic musks in WWTPs.

Synthetic musks have been used for a long time in personal care and household products. In recent years, this continuous input has increased considerably, to the point that they were recognized as emerging pollutants by the scientific community, due to their persistence in the environment, and hazardous potential to ecosystems even at low concentrations. The number of studies in literature describing their worldwide presence in several environmental matrices is growing, and many of them indicate that the techniques employed for their safe removal tend to be ineffective. This is the case of conventional activated sludge treatment plants (WWTPs), where considerable loads of synthetic musks enter mainly through domestic sewage. This review paper compiles and discusses the occurrence of these compounds in the sewage, effluents and sludge, main concentration levels and phase distributions, as well as the efficiency of the different methodologies of removal applied in these treatment facilities. To the present day, it has been demonstrated that WWTPs lack the ability to remove musks completely. This shows a clear need to develop new effective and cost-efficient remediation approaches and foresees potential for further improvements in this field.

Biomonitoring of pesticides by pine needles — Chemical scoring, risk of exposure, levels and trends

Vegetation is a useful matrix for the quantification of atmospheric pollutants such as semi-volatile organic compounds (SVOCs). In particular, pine needles stand out as effective biomonitors due to the excellent uptake properties of their waxy layer. Having previously validated an original and reliable method to analyse pesticides in pine needles, our work team set the objective of this study to determine the levels of 18 pesticides in Pinus pinea needles collected in 12 different sampling sites in Portugal. These compounds were selected among a total of 70 pesticides by previous chemical scoring, developed to assess their probability to occur in the atmosphere. The risk of exposure was evaluated by the binomial chemical score/frequency of occurrence in the analysed samples. Levels and trends of the chemical families and target of the pesticides were obtained regarding the type of land occupation of the selected sites, including the use of advanced statistics (principal component analysis, PCA). Finally, some correlations with several characteristics of the sampling sites (population, energy consumption, meteorology, etc.) were also investigated.

An analytical multi-residue approach for the determination of semi-volatile organic pollutants in pine needles

Vegetation (and pine needles in particular) has been widely used as an alternative to other conventional sampling devices to assess the atmospheric presence of semi-volatile organic contaminants (SVOCs). While most analytical procedures developed focus only on one or two chemical classes, this this work intends to establish a multi-component protocol to quantify brominated flame-retardants (BFRs), polychlorinated biphenyls (PCBs), organochlorine pesticides (OCPs), polynuclear aromatic hydrocarbons (PAHs) and one class of contaminant of emerging concern, the synthetic musks fragrances (SMCs). Pine needles extracts were obtained by ultrasonic solvents extraction (USE), and different cleanup approaches using solid-phase extraction (SPE) employing combinations of sorbents and solvents as well as gel permeation chromatography (GPC) were tested. SPE with alumina followed by GCP yielded the best results, with average recoveries over 80%. The application of the method under field conditions was proven by the analysis of naturally contaminated samples from 3 sites of different potential exposure (remote, rural and urban). The total detected concentrations ranged from 0.45 to 0.87 ng g(-1) dry weight (dw) for BFRs, 0.35 to 1.01 ng g(-1) (dw) for PCBs, 0.36 to 12.2 ng g(-1) (dw) for HCB, 245.7 to 967.8 ng g(-1) (dw) for PAHs and 20.7 to 277.5 ng g(-1) (dw) for SMCs. This methodology is a viable approach for the simultaneous analysis of five different classes of atmospheric pollutants employing less analytical efforts. Moreover, to the authors best knowledge, this is also the first time vegetation is employed in the detection of SMCs.

Implantable Flexible Pressure Measurement System Based on Inductive Coupling

One of the currently available treatments for aortic aneurysms is endovascular aneurysm repair (EVAR). In spite of major advances in the operating techniques, complications still occur and lifelong surveillance is recommended. In order to reduce and even eliminate the commonly used surveillance imaging exams, as well as to reduce follow-up costs, new technological solutions are being pursued. In this paper, we describe the development, including design and performance characterization, of a flexible remote pressure measurement system based on inductive-coupling for post-EVAR monitoring purposes. The telemetry system architecture and operation are described and main performance characteristics discussed. The implantable sensor details are provided and its model is presented. Simulations with the reading circuit and the sensors model were performed and compared with measurements carried out with air and a phantom as media, in order to characterize the telemetry system and validate the models. The transfer characteristic curve (pressure versus frequency) of the monitoring system was obtained with measurements performed with the sensor inside a controlled pressure vacuum chamber. Additional experimental results which proof the system functionality were obtained within a hydraulic test bench that emulates the aorta. Several innovative aspects, when compared to the state of the art, both in the sensor and in the telemetry system were achieved.

Characterization of the electrode-skin impedance of textile electrodes

Wearable systems are expected to contribute for improving traditional biopotential signals monitoring devices due to higher freedom and unobtrusiveness provided to the wearer. Textile electrodes present advantages compared with the conventional Ag/AgCl electrodes for the capturing of biopotentials, namely in terms of skin irritation due to the hydrogel and the need of a technician to place the electrodes on the correct positions. Due to the lack of hydrogel, textile electrodes present different electrical contact characteristics. The skin-electrode impedance is an important feature since it affects the captured signal quality. Although a low impedance is desired, a comfortable wearable system should not require the electrodes to be covered by the hydrogel or be moistened. A forearm sleeve provided with textile electrodes was used to study the electrode-skin impedance and the signal-to-noise ratio (SNR) of surface electromyographic (EMG) signals on a long-term use basis. The sleeve can be adjusted for different levels of tightening to control the pressure applied on the electrodes. The obtained results provide valuable information on the pressure that the textile garments of a sleeve or vest should apply on the recording electrodes, in order to assure a good electrical and mechanical contact between the electrodes and the skin and decrease the noise due to motion. It was observed that the electrode-skin impedance measurement alone is not sufficient to establish a relation with the SNR. The extraction of parameters from an electrical equivalent model of the electrode-skin interface allows to determine a relation with the model parameters and the SNR. The evaluation of these parameters during long-term monitoring will allow assessing the quality of biopotential measurements in textile electrodes.

A true power detector for RF PA built-in calibration and testing

Different built-in self testing schemes for RF circuits have been developed resorting to peak voltage detectors. These are simple to implement but provide a conditional RF power measurement accuracy as impedance is assumed to be known. A true power detector is presented which allows obtaining more accurate measurements, namely as far as output load variations are concerned. The theoretical fundaments underlining the power detector operating principle are presented and simulation and experimental results obtained with a prototype chip are described which confirm the benefits of measuring true power, comparing to output peak voltage, when observing output load matching deviations and complex waveforms.

Architecture of test support ICs for mixed-signal testing

Discusses the need of a test infrastructure to support the testing of mixed-signal electronic systems, and discusses a general architecture for test support ICs that can be used to build it. An implementation of a subset of this architecture is described together with its application in a practical example.<<ETX>>

Novel textile systems for the continuous monitoring of vital signals: design and characterization.

In this article we present a smart textile system for the continuous monitoring of cardiorespiratory signals, produced and integrated with an industrial embroidery unit. The design of a T-shirt system, having embedded textile sensors and interconnects and custom designed circuit for data collection and Bluetooth transmission is presented. The performance of skin-contact textile electrodes, having distinctive electrical characteristics and surface morphologies, was characterized by measurements of signal to noise ratio, under dry and moisture conditions. The influence of the electrodes size and the wear resistance were addressed. Results of an electrocardiogram acquisition with a subject wearing the T-shirt and display on a smartphone are also shown. The presented smart textile systems exhibit good performance and versatility for custom demand production.

Towards a Dependable Cardiovascular Surveillance System

An aneurysm is a life-threatening condition,which left untreated may burst or rupture, causing massive blood loss. One of the currently available treatments for aortic aneurysms is endovascular aneurysm repair (EVAR). However, in spite of major advances in the surgical techniques, complications are still likely to occur making it recommendable to maintain lifelong surveillance. In order to reduce and even eliminate current surveillance imaging exams, as well as to reduce follow-up costs, new technological solutions are being pursued. The work presented herein aims to develop a novel and dependable non- invasive coronary stent-graft monitoring system based on RFID technology. The monitoring system uses an inductive coupling interface to capture the pressures given by a cluster of sensors placed on the stent-graft’s wall. The application of multimodal data fusion techniques enables the improvement of the surveillance system performance in terms of accuracy, robustness and reliability. The processing of the pressure signalsmeasured inside the aneurysm sac with other physiological signals - electrocardiogram (ECG) and arterial blood pressure (ABP) - will allow obtaining better monitoring resolution and reliability. The techniques utilized to diagnose deviations fromthe normal operation or faults in the flexible pressure sensors are described and tested, showing promising results for achieving a highly reliable system.