Generation of synthetic wide-band electromagnetic time series

The estimation of the earth transfer functions in MT prospecting method poses the greatest difficulty. As in the seismic prospecting method this task requires the development of advanced processing techniques. In order to assess the performance of each technique, controlled synthetic data and different noise types, which simulate the observed signals, are required. This paper presents a procedure to generate a wide-band noise-free electromagnetic field to be used both for magnetotelluric and audio-magnetotelluric studies. Furthermore, an effort was made to extend the simulation procedures to generally stratified and simple inhomogeneous earth structures. The discrete-time magnetic field values are generated through the inverse Fourier transform of a continuous amplitude spectrum and a sampling procedure. The electric field time series are obtained by the convolution of the magnetic field time series, calculated in the interested frequency band, with a non-causal impedance impulse response. Polarized fields, which are important when inhomogeneous media are considered, are also generated

Generation of synthetic wide-band electromagnetic time series

The estimation of the earth transfer functions in MT prospecting method poses the greatest difficulty. As in the seismic prospecting method this task requires the development of advanced processing techniques. In order to assess the performance of each technique, controlled synthetic data and different noise types, which simulate the observed signals, are required. This paper presents a procedure to generate a wide-band noise-free electromagnetic field to be used both for magnetotelluric and audio-magnetotelluric studies. Furthermore, an effort was made to extend the simulation procedures to generally stratified and simple inhomogeneous earth structures. The discrete-time magnetic field values are generated through the inverse Fourier transform of a continuous amplitude spectrum and a sampling procedure. The electric field time series are obtained by the convolution of the magnetic field time series, calculated in the interested frequency band, with a non-causal impedance impulse response. Polarized fields, which are important when inhomogeneous media are considered, are also generated

Stability analysis of apparent resistivity measurement in the seismically active area of Val d'Agri (southern Italy)

International audienceA magnetotelluric monitoring station has been installed in the Val d'Agri area (southern Italy), to investigate the physics underlying the generation mechanisms of the electrokinetic effect, due to rapid pore pressure changes and fluid flows near the focal area of incoming earthquakes. It is well known that the magnetotelluric method reveals variations in electrical resistivity within the Earth at large depths, reaching within appropriate frequency bands the Earth's mantle. Depth sounding is performed by measuring the ratio between the mutually perpendicular horizontal electric and magnetic fields at the earth's surface, furnishing the apparent resistivity, which describes the electrical properties of subsoil as function of depth. The selected site of Val d'Agri has been struck by strong seismic events in past and recent years, this suggesting the investigation of possible changes in apparent resistivity correlated with the local tectonic activity. We analyzed the stability of the measurement of apparent resistivity and phase of the impedance tensor Z(?) during time. Our findings suggest that the measure of apparent resistivity during night-time is more stable. Therefore, we identified the characteristic apparent resistivity curve of the subsoil of the Val d'Agri site, which could be considered as a reference

Shallow to intermediate resistivity features of the Colfiorito Fault System inferred by DC and MT survey

Over the last decade electromagnetic (EM) measurements have provided new constraints on the upper-crustal structure of the major fault zones in the world, both when they act as conduit and as a barrier, due to strong sensitivity of resistivity to fluids circulation and mineralization. On the track of a high impact magnetotelluric (MT) study performed across the San Andreas Fault, high resolution EM data were collected in the Colfiorito epicentral area along profiles crossing some main fault lineaments. Being the study focussed both on shallow that on intermediate resistivity distribution in the brittle upper-crust, a MT profile was integrated by several electrical resistivity tomographies (ERT). The latter were successful in locating faults even where the structures are buried by a wide covering of Quaternary deposits and in the recognition of different electrical signatures of the faults. MT resistivity model crossing Mt. Prefoglio normal fault clearly imaged the typical thrust structures of the area and a high conductive zone spatially related to the fault. Seismicity seems to be located outside such conductive area, whose behaviour suggests a fluidised and altered zone incapable of supporting significant stress internally

Magneto-seismic interpretation of subsurface volcanism in the Gaeta Gulf (Italy, Tyrrhenian Sea)

The occurrence of a former subaerial volcanic edifice off the Volturno River (Tyrrhenian Sea, Gulf of Gaeta) in the 41°N parallel is suggested by joint interpretation of multichannel seismic lines and ship-borne magnetic data. In the Campanian region igneous (volcanic) rocks are very close to the carbonate Mesozoic basement and seismics cannot always discriminate between them. A joint seismic-magnetic analysis was very effective in assessing the lithological nature of the bodies evidenced by both geophysical methods. Distortion analysis showed that the main magnetic source in the area is characterised by a not normal-polarity direction of the magnetization, similar to other Pleistocene volcanoes in the Tyrrhenian region. Hence we argued that the overall magmatic emplacement for this source occurred during a reverse-polarity chron, very likely the 0.78-1.78 Ma time span. This magnetically-derived time constraint is in agreement with seismic stratigraphy that shows that the entire volcano is sealed by the Volturno River prograding delta from Middle Pleistocene to Present in age. Our interpreted volcano belongs to a set of inferred onshore and offshore volcanic edifices all lying along the 41°N paralle

A new magnetotelluric monitoring network operating in Agri Valley (Southern Italy): study of stability of apparent resistivity estimates

Variations detected in geophysical, especially electromagnetic, parameters in seismic active areas have been sometimes attributed to modifications of the stress field. Among the different geophysical methods, magnetotellurics (MT) could be one of the most effective because it allows us to explore down to seismogenic depths. Continuous MT recording could allow us to evaluate whether possible variations are significantly correlated with the seismic activity of investigated area. To assess the significance of such observations we must be able to say how well an apparent resistivity curve should be reproduced when measurements are repeated at a later time. To do this properly it is essential to know that the estimated error bars accurately represent the true uncertainties in comparing the transfer functions. In this work we will show the preliminary results obtained from the analysis of the data coming from the new MT monitoring network installed in Agri Valley. This analysis gives us the possibility: i) to better study the temporal stability of the signals, ii) to better discriminate the noise affecting the measures by remote reference estimation. The performed analysis disclosed a relatively low degree of noise in the investigated area, which is a promising condition for monitoring

Emotions and dog bites: Could predatory attacks be triggered by emotional states?

Dog biting events pose severe public health and animal welfare concerns. They result in several consequences for both humans (including physical and psychological trauma) and the dog involved in the biting episode (abandonment, relocation to shelter and euthanasia). Although numerous epidemiological studies have analyzed the different factors influencing the occurrence of such events, to date the role of emotions in the expression of predatory attacks toward humans has been scarcely investigated. This paper focuses on the influence of emotional states on triggering predatory attacks in dogs, particularly in some breeds whose aggression causes severe consequences to human victims. We suggest that a comprehensive analysis of the dog bite phenomenon should consider the emotional state of biting dogs in order to collect reliable and realistic data about bite episodes

A multimodal retina-iris biometric system using the levenshtein distance for spatial feature comparison

The recent developments of information technologies, and the consequent need for access to distributed services and resources, require robust and reliable authentication systems. Biometric systems can guarantee high levels of security and multimodal techniques, which combine two or more biometric traits, warranting constraints that are more stringent during the access phases. This work proposes a novel multimodal biometric system based on iris and retina combination in the spatial domain. The proposed solution follows the alignment and recognition approach commonly adopted in computational linguistics and bioinformatics; in particular, features are extracted separately for iris and retina, and the fusion is obtained relying upon the comparison score via the Levenshtein distance. We evaluated our approach by testing several combinations of publicly available biometric databases, namely one for retina images and three for iris images. To provide comprehensive results, detection error trade-off-based metrics, as well as statistical analyses for assessing the authentication performance, were considered. The best achieved False Acceptation Rate and False Rejection Rate indices were and 3.33%, respectively, for the multimodal retina-iris biometric approach that overall outperformed the unimodal systems. These results draw the potential of the proposed approach as a multimodal authentication framework using multiple static biometric traits

Prevalence of functional dyspepsia and its subgroups in patients with eating disorders

AIM: To study the prevalence of functional dyspepsia (FD) (Rome III criteria) across eating disorders (ED), obese patients, constitutional thinner and healthy volunteers. METHODS: Twenty patients affected by anorexia nervosa, 6 affected by bulimia nervosa, 10 affected by ED not otherwise specified according to diagnostic and statistical manual of mental disorders, 4th edition, nine constitutional thinner subjects and, thirty-two obese patients were recruited from an outpatients clinic devoted to eating behavior disorders. Twenty-two healthy volunteers matched for age and gender were enrolled as healthy controls. All participants underwent a careful clinical examination. Demographic and anthropometric characteristics were obtained from a structured questionnaires. The presence of FD and, its subgroups, epigastric pain syndrome and postprandial distress syndrome (PDS) were diagnosed according to Rome III criteria. The intensity-frequency score of broader dyspeptic symptoms such as early satiety, epigastric fullness, epigastric pain, epigastric burning, epigastric pressure, belching, nausea and vomiting were studied by a standardized questionnaire (0-6). Analysis of variance and post-hoc Sheffè tests were used for comparisons. RESULTS: 90% of patients affected by anorexia nervosa, 83.3% of patients affected by bulimia nervosa, 90% of patients affected by ED not otherwise specified, 55.6% of constitutionally thin subjects and 18.2% healthy volunteers met the Postprandial Distress Syndrome Criteria (χ2, P < 0.001). Only one bulimic patient met the epigastric pain syndrome diagnosis. Postprandial fullness intensity-frequency score was significantly higher in anorexia nervosa, bulimia nervosa and ED not otherwise specified groups compared to the score calculated in the constitutional thinner group (4.15 ± 2.08 vs 1.44 ± 2.35, P = 0.003; 5.00 ± 2.45 vs 1.44 ± 2.35, P = 0.003; 4.10 ± 2.23 vs 1.44 ± 2.35, P = 0.002, respectively), the obese group (4.15 ± 2.08 vs 0.00 ± 0.00, P < 0.001; 5.00 ± 2.45 vs 0.00 ± 0.00, P < 0.001; 4.10 ± 2.23 vs 0.00 ± 0.00, P < 0.001, respectively) and healthy volunteers (4.15 ± 2.08 vs 0.36 ± 0.79, P < 0.001; 5.00 ± 2.45 vs 0.36 ± 0.79, P < 0.001; 4.10 ± 2.23 vs 0.36 ± 0.79, P < 0.001, respectively). Early satiety intensity-frequency score was prominent in anorectic patients compared to bulimic patients (3.85 ± 2.23 vs 1.17 ± 1.83, P = 0.015), obese patients (3.85 ± 2.23 vs 0.00 ± 0.00, P < 0.001) and healthy volunteers (3.85 ± 2.23 vs 0.05 ± 0.21, P < 0.001). Nausea and epigastric pressure were increased in bulimic and ED not otherwise specified patients. Specifically, nausea intensity-frequency-score was significantly higher in bulimia nervosa and ED not otherwise specified patients compared to anorectic patients (3.17 ± 2.56 vs 0.89 ± 1.66, P = 0.04; 2.70 ± 2.91 vs 0.89 ± 1.66, P = 0.05, respectively), constitutional thinner subjects (3.17 ± 2.56 vs 0.00 ± 0.00, P = 0.004; 2.70 ± 2.91 vs 0.00 ± 0.00, P = 0.005, respectively), obese patients (3.17 ± 2.56 vs 0.00 ± 0.00, P < 0.001; 3.17 ± 2.56 vs 0.00 ± 0.00, P < 0.001 respectively) and, healthy volunteers (3.17 ± 2.56 vs 0.17 ± 0.71, P = 0.002; 3.17 ± 2.56 vs 0.17 ± 0.71, P = 0.001, respectively). Epigastric pressure intensity-frequency score was significantly higher in bulimic and ED not otherwise specified patients compared to constitutional thin subjects (4.67 ± 2.42 vs 1.22 ± 1.72, P = 0.03; 4.20 ± 2.21 vs 1.22 ± 1.72, P = 0.03, respectively), obese patients (4.67 ± 2.42 vs 0.75 ± 1.32, P = 0.001; 4.20 ± 2.21 vs 0.75 ± 1.32, P < 0.001, respectively) and, healthy volunteers (4.67 ± 2.42 vs 0.67 ± 1.46, P = 0.001; 4.20 ± 2.21 vs 0.67 ± 1.46, P = 0.001, respectively). Vomiting was referred in 100% of bulimia nervosa patients, in 20% of ED not otherwise specified patients, in 15% of anorexia nervosa patients, in 22% of constitutional thinner subjects, and, in 5.6% healthy volunteers (χ2, P < 0.001). CONCLUSION: PDS is common in eating disorders. Is it mandatory in outpatient gastroenterological clinics to investigate eating disorders in patients with PDS