S. La Malfa

Citrus phylogeny and genetic origin of important species as investigated by molecular markers.

Abstract Citrus phylogeny was investigated using RAPD, SCAR and cpDNA markers. The genotypes analyzed included 36 accessions belonging to Citrus together with 1 accession from each of the related genera Poncirus, Fortunella, Microcitrus and Eremocitrus. Phylogenetic analysis with 262 RAPDs and 14 SCARs indicated that Fortunella is phylogenetically close to Citrus while the other three related genera are distant from Citrus and from each other. Within Citrus, the separation into two subgenera, Citrus and Papeda, designated by Swingle, was clearly observed except for C. celebica and C. indica. Almost all the accessions belonging to subgenus Citrus fell into three clusters, each including 1 genotype that was considered to be a true species. Different phylogenetic relationships were revealed with cpDNA data. Citrus genotypes were separated into subgenera Archicitrus and Metacitrus, as proposed by Tanaka, while the division of subgenera Citrus and Papeda disappeared. C. medica and C. indica were quite distant from other citrus as well from related genera. C. ichangensis appeared to be the ancestor of the mandarin cluster, including C. tachibana. Lemon and Palestine sweet lime were clustered into the Pummelo cluster led by C. latipes. C. aurantifolia was located in the Micrantha cluster. Furthermore, genetic origin was studied on 17 cultivated citrus genotypes by the same molecular markers, and a hybrid origin was hypothesized for all the tested genotypes. The assumptions are discussed with respect to previous studies; similar results were obtained for the origin of orange and grapefruit. Hybrids of citron and sour orange were assumed for lemon, Palestine sweet lime, bergamot and Volkamer lemon, while a citron × mandarin hybrid was assumed for Rangpur lime and Rough lemon. For Mexican lime our molecular data indicated C. micrantha to be the female parent and C. medica as the male one.

Experimental investigations on the spatial resolution in RTD-Fluxgates

This paper discusses about the spatial resolution performance on RTD-fluxgate prototypes having different ferromagnetic core geometry. This is of major importance when the magnetic target signal source is very confined in space and therefore the ability of the sensor to correctly point the target is dictated by its ability to resolve the target position. The readout strategy is based on the use of the residence times difference (RTD), where the DC magnetic field information is derived from the temporal positions of the output waveform spikes. The experiments and studies reported here give guidelines for the optimal design in terms of spatial sensing capabilities. The ability of the sensor to locate the position of a DC B-field source is therefore characterized and related to the shape of the core adopted for the sensor fabrication. Two core types have been considered: ribbon and wire. 3 D diagrams have been developed in order to evaluate the time domain response as function of a known magnetic source position.

Adaptive Modeling of Hysteretic Magnetometers

Magnetic hysteresis is one example of the nonlinearity that underpins many practical applications, particularly in the field of magnetic sensors such as fluxgate magnetometers. The aim of this paper is to present a behavioral model that is suitable for the circuital simulation of fluxgate magnetometers in standard simulators like Simulation Program with Integrated Circuit Emphasis (SPICE). The main advantage of the proposed methodology, vis-a-vis the traditional model, is the efficiency in predicting the behavior of amorphous materials with sharp hysteresis loops. Moreover, the developed model is easily implementable in any SPICE-like simulator and can be adopted for a wide range of operating conditions. The modeling strategy has been assessed by the comparison of predicted and observed behaviors of fluxgate magnetometers.

SPICE simulation of coupled core fluxgate magnetometers

SPICE simulation is universally recognized as a powerful tool in the field of electronic engineering. These simulations are, particularly useful for dealing with a strong nonlinear behavior that cannot be easily handled analytically. Magnetic hysteresis is one example of a non-linearity that underpins many practical applications, especially in the field of magnetometers and magnetic sensors. The aim of this paper is to present a behavioral model of magnetic hysteresis applied to the numerical simulation of coupled core fluxgate magnetometers

ROC analysis for RTD Fluxgate magnetometers

The aim of this paper is to present preliminary experimental results on the performance of RTD Fluxgate magnetometers in security applications. The presence of a metallic object near the sensor can be detected by measuring the weak perturbation of geomagnetic field distribution produced by the magnetic permeability of the material from which the object is made. Results are presented by the use of ROC curves, a widely used formalism to evaluate the performance of binary classifiers.

Perming Effect in Residence Times Difference Fluxgate Magnetometers

The aim of this paper is to present experimental results on the estimation of perming effect in two different experimental prototypes of fluxgate magnetometer based on the Residence Times Difference (RTD) readout strategy. The perming effect can affect the output signal of the device (by an offset) after a magnetic shock. It is similar to hysteresis, but the applied field must be much higher than the full–scale range. All the sensors containing ferromagnetic material are susceptible to perming. The obtained experimental results allow for the definition of guidelines for the optimal re–magnetization strategy of the ferromagnetic core in the particular case of RTD fluxgate magnetometers.

Advanced dynamic magnetometer for persistent surveillance

We present an overview of the “coupled-core” fluxgate magnetometer and its “single-core” counterpart. The basic theory is briefly discussed and some prototype realizations presented via a set of assorted applications. In particular, the results of sea-tests carried out, in collaboration with FOI-Stockholm, in the Baltic Sea will be presented and discussed together with other experimental results in the area of intrusion detection.