Mauro Parodi

Comparison between a LAPS and an FET-based sensor for cell-metabolism detection

Several silicon-based biosensors have been developed for various applications, such as enzymatic and immunological activity determination and cell-metabolism detection. This work describes an electrochemical characterization of ion-sensitive field-effect transistor (ISFET) and light-addressable potentiometric sensor (LAPS) transducers and a test of such devices as detectors of 3T6 (Swiss albino mouse embryo, fibroblasts) metabolism. In particular, our investigation is devoted to some fundamental parameters of these transducers (e.g., pH sensitivity, drift, temperature dependence of the output signal, speed of response) for the purpose of comparing their performance related to cell-metabolism evaluation. The final goal is therefore to analyze the capabilities of these silicon-based transducers for use in a biosensing system for cell-metabolism detection.

Launcher and microstrip characterization

A method for identifying scattering parameters of launchers and uniform microstrips is presented. It is shown that 8 complex measurements (magnitude and phase) on two microstrips which are different only in length, inserted between two launchers, can give, with suitable algebraic treatment, the S-parameters of either the microstrips and the launchers. This technique is promising for deembedding active devices as well for microstrip discontinuities.

A modular supervised algorithm for vessel segmentation in red-free retinal images

In this paper, a supervised algorithm for vessel segmentation in red-free images of the human retina is proposed. The algorithm is modular and made up of two fundamental blocks. The optimal values of two algorithm parameters are found out by maximizing proper measures of performances (MOPs) able to evaluate from a quantitative point of view the results provided by the proposed algorithm. The choice of the MOP allows one to tailor the solution to the specific image features to be emphasized. The performances of the algorithm are compared with those of other methods described in the literature. The simulation results show a good trade-off between quality and processing speed times. For instance, in terms of the maximum average accuracy (MAA), K value, and specificity (SP), the best performance outcomes are 0.9587, 0.8069 and 0.9477, respectively.

Synthesis of nonlinear multiport resistors: a PWL approach

This paper presents a method for the approximate synthesis of nonlinear multiport resistors. According to some fundamental circuit theory results, the general problem of synthesizing a multiport resistor with given constitutive equations corresponds to that of the synthesis of nonlinear controlled sources. Following this idea, in this paper, we focus on the design of nonlinear controlled sources using a piecewise-linear (PWL) approach. The constitutive equations are first approximated by resorting to canonical expressions for continuous PWL functions, and then implemented using a set of elementary building blocks. The proposed method is applied to the synthesis of the nonlinear resistive part of an equivalent circuit of the Hodgkin-Huxley nerve membrane model.

Synthesis of multiport resistors with piecewise-linear characteristics: a mixed-signal architecture

Non-linear multiport resistors are the main ingredients in the synthesis of non-linear circuits. Recently, a particular PWL representation has been proposed as a generic design platform (IEEE Trans. Circuits Syst.-I 2002; 49:1138–1149). In this paper, we present a mixed-signal circuit architecture, based on standard modules, that allows the electronic integration of non-linear multiport resistors using the mentioned PWL structure. The proposed architecture is fully programmable so that the unit can implement any user-defined non-linearity. Moreover, it is modular: an increment in the number of input variables can be accommodated through the addition of an equal number of input modules. Copyright

A PWL ladder circuit which exhibits hysteresis

A circuit model for static hysteresis is presented. the circuit has a ladder structure with linear capacitors and piece wise linear resistors. the model behaviour shows all basic characteristics of static hysteresis phenomena. the model is put into relation with others proposed in the literature. an analysis of the model properties and a detailed comparison with the static Preisach model are made.

A method for the approximate synthesis of cellular non‐linear networks—Part 1: Circuit definition

In this paper, we face the problem of the synthesis of cellular non-linear networks (CNNs) able to find approximate solutions of either partial differential equations or functional minimization problems. In particular, the paper deals with the approximate synthesis of the multi-terminal resistors that include all the non-linearities of such dynamic circuits. The proposed approximation method is based on the piecewise-linear (PWL) approach developed by Julian et al. in the last few years, but it resorts to a different definition of the inner product and hence to other PWL basis functions. The method is applied to a case-study concerning a CNN devoted to image processing. Copyright

LEARNING OPTIMIZATION OF NEURAL NETWORKS USED FOR MIMO APPLICATIONS BASED ON MULTIVARIATE FUNCTIONS DECOMPOSITION

An approach based on multivariate function decomposition is presented with the aim of performing the learning optimization of multi-input-multi-output (MIMO) feed-forward neural networks (NNs). The proposed approach is mainly dedicated to all those cases in which the training set used for the learning process of MIMO NNs is sizeable and consequently the learning time and the computational cost are too large for an effective use of NNs. The basic idea of the presented approach comes from the fact that it is possible to approximate a multivariate function by means of a series containing only univariate functions. On the other hand, in many practical cases, the conversion of a MIMO NN into several multi-input-single-output (MISO) NNs is frequently adopted and investigated into state-of-the-art NNs. The proposed method introduces a further transformation, i.e. the decomposition of a MISO NN into a collection of single-input-single-output (SISO) NNs. This MISO–SISOs decomposition is performed using the previously cited series coming from the technique of the multivariate decomposition of functions. In this way, each SISO NN can be trained on each one-dimensional function returned from the cited decomposition, i.e. using limited data. Moreover, the present approach is easy to be implemented on a parallel architecture. In conclusion, the presented approach allows us to treat a MIMO NN as a collection of SISO NNs. Experimental results will be shown with the aim of proving that the proposed method is effective for a strong reduction of learning time by preserving anyway the accuracy.

A hysteresis‐based chaotic circuit: dynamics and applications

In this paper, a chaotic circuit based on a hysteretic mechanism is presented and analysed. The circuit is made up of a linear part and a hysteretic cell where the only non-linear elements are two piecewise-linear two-terminal resistors. The dynamics of the circuit is discussed in detail so as to evidence its possible different behaviours. A possible utilization of the circuit as the basis for a transmitter–receiver system is also proposed. The discussion is supported by numerical examples. Copyright

Towards analog implementations of PWL two-dimensional non-linear functions

This paper deals with the circuit implementation of non-linear algebraic bivariate functions. The synthesis procedure is based on a piecewise-linear approximation technique and on a corresponding circuit architecture, whose basic element is a circuit block with the input/output function y(x) = max(0; x). Some known CMOS circuit structures that can be used to obtain such a block are considered, and their main advantages and drawbacks are pointed out. The static and dynamic features of both the single circuit block and the overall architecture for two-dimensional PWL functions are illustrated by way of examples. Copyright