We have applied VIS-NIR diffuse reflectance spectroscopy to study different human skin lesions. A new set of features has been derived through the analysis of their spectra to discriminate among normal skin and skin lesions.
Pigmented skin lesions have been studied by optical diffuse reflectance spectroscopy. Our measure system consists of a portable visible near infrared (550-1000 nm) spectrometer, tungsten-halogen lamp and fibre optic probes. The system was tested in steady state conditions. After that, a reproducibility study of normal and pigmented skin spectra was carried out. A small scale study has been conducted in human volunteers with different clinically evaluated lesions. The analysis of the collected spectra is shown.
Integrated inductors are key components in Radio Frequency Integrated Circuits (RFICs) because they are needed in several building blocks, such as voltage-controlled oscillators (VCOs), low-noise amplifiers (LNAs), mixers, or filters. The cost reduction, achieved in the circuit assemblage, makes them preferable to Surface Mounted Devices in spite of the different sources of lost that limits the use of integrated inductors; there are losses associated with the semiconductor substrate, and losses in the metals. We report, in this work, our research in modeling integrated inductors, particularly the losses in the metals. The model is derived from measurements taken from integrated spiral inductors designed and fabricated in a standard silicon process. The measurements reveal that the widely accepted lumped equivalent model does not properly predict the integrated inductor behavior at frequencies above 3 GHz for our technology. We propose a simple modification in the lumped equivalent circuit model: the introduction of an empirical resistor in the port 1-to-port 2 branch of the equivalent circuit. As a result, it will be demonstrated that the integrated inductor behavior is adequately predicted in a wider frequency range than does the conventional model. We also report a new methodology for characterizing the integrated inductors including the new resistor. In addition, the new model is used to build-up an integrated inductor library containing optimized integrated inductors.
This work analyses the DC response of an InGaAs channel PHFET when varying temperature. An analytic model for the drain current is derived from previous work, incorporating the extrinsic resistances. Experimental output characteristics at different temperatures are compared with those offered by the resulting model and numerical simulations. The DC drain current is obtained introducing the external voltages applied to the HFET terminals into an intrinsic model. The temperature range considered in this paper is between 300 and 400 K. In this range, the temperature dependence of the intrinsic electrical parameters is included in the model. For the temperature dependence of the extrinsic resistances, the HFET is numerically simulated with MINIMOS-NT. As far as we know, any influence of the electron transport through the AlGaAs/InGaAs heterojunction on the extrinsic resistances has not been already established. In our case, a termionic-field-emission (TFE) is used to simulate this effect (without TFE not only the drain current is underestimated, but also the temperature dependence predicted is opposite to the actual).
As result, the extrinsic source resistence is nearly constant (7.5 ohms), and higher values are obtained for the extrinsic drain resistence, which has a linear and positive temperature dependence, raising as the transistor operates in saturation region. When the drain voltage diminishes, the influence of the TFE model on the extrinsic resistances vanishes, and RD tends to RS. The drain current predicted by the model, in linear and saturation region, shows a relative error between measured and modeled values smaller than 10%.
The increase in the incidence of pigmented skin lesions in the last decade together with the fact that early detection could allow a mortality reduction has lead to the development of spectrometric diagnostic techniques applicable to dermatology. These techniques are based on the evidence that the presence of malignant cells should somehow alter the optical characteristics of epidermis with respect to the healthy one and a different reflectance spectrum should appear. The subjectivity of the clinical observation by the specialist is, in this way, substituted by an objective technique, with the improve of the specificity and the sensitivity. The aim of this work is to obtain a skin reflectance database of both benign and malignant lesions as well as of healthy skin which permits to establish algorithms and discrimination rules for a more objective identification of different pigmented skin lesions. The measure system consists of a portable visible near infrared (600-1000 nm) spectrometer (AVS-USB200, Avantes), a tungsten halogen lamp (HL-200) and fiber optics reflection probes. The parameters of that system and their variability has been tested in steady state conditions by using neutral filters and a white reference tile. A reproducibility study of both normal and pigmented skin diffuse reflectance spectra has been carried out. After that a small scale study of selected subjects have been conducted. This study has comprised the collection of spectra from different skin pigmented lesions and the clinical evaluation of its lesions characteristics by the dermatologist. The results after the analysis of the collected data are presented.
Two decades ago, the first application of surface plasmon resonance phenomenon (SPR) was presented; from then on the improvement on the sensor instrumentation is the key factor for the system accuracy, opening infinity of derived applications of the new optoelectronics sensors investigation. The high specificity surface plasmon resonance sensor presented is based on two photodiode arrays, one for referential measurement and other for the selective detection of substance. This report shows several solutions that contribute to the optimization of the design of electronic acquisition that treats weak signals in noisy electronic media. The design improvements are based on the minimization of the noise in electronic circuits versus digital signal processing limitations. This work solves the inherent problems in circuits design where photodiodes arrays and analog multiplexer are used by means of the dynamic control of the high gain amplifiers chain offsets in transimpedance classic configuration, in the good adjustment of the ADC measurement spectrum bandwidth and in the compensation in real time, with electronic circuits, of the optical noise effects, as dark currents. This optimization is reached after parameterize the process by means of the device self-calibration that will allow to improve the fidelity of the measures notably, this is essential when the variations of the plasmon sensor refraction index to detect has an order of 1e-6.
A transmittance pulse oximetry system based on near-infrared laser diodes (LD) for monitoring arterial blood hemoglobin oxygen saturation (So2) has been previously reported. In this work we present the results obtained after improvements in the sensor configuration, signal processing algorithm and calibration procedure. The pulse oximetry system also comprises the sensor electronics, and a data acquisition board installed on a handheld personal computer. The two LD chips are mounted on a single metal heat-sink and as photo- detectors are used silicon p-i-n photodiodes with the first amplifier stage situated in their back side. The real time calculation of the parameters related to So2 is carried out through a numeric separation of the pulsatile and non- pulsatile components of the photoplethysmographic signals for both wavelengths and a non-linear filtering. Patients with respiratory failure conditions were monitored as a part of the calibration procedure in order to cover a wide range of So2-values. A calibration curve have been derived through the determination of in vitro arterial So2 with a significant quantity of experimental points ranging from 60 to almost 100%. The obtained results demonstrate that it is possible to apply the proposed system to monitoring a wide range of oxygen saturation levels.
A transmittance pulse oximeter based on near-infrared laser diodes for monitoring arterial blood hemoglobin oxygen saturation has been developed and tested. The measurement system consists of the optical sensor, sensor electronics, acquisition board and personal computer. The system has been tested in a two-part experimental study involving human volunteers. A calibration curve was derived and healthy volunteers were monitored under normal and apnea conditions, both with the proposed system and with a commercial pulse oximeter. The obtained results demonstrate the feasibility of using a sensor with laser diodes emitting at specific near-infrared wavelengths for pulse oximetry.
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