Potential shallow aquifers characterization through an integrated geophysical method: multivariate approach by means of k-means algorithms

The need to obtain a detailed hydrogeological characterization of the subsurface and its interpretation for the groundwater resources management, often requires to apply several and complementary geophysical methods. The goal of the approach in this paper is to provide a unique model of the aquifer by synthesizing and optimizing the information provided by several geophysical methods. This approach greatly reduces the degree of uncertainty and subjectivity of the interpretation by exploiting the different physical and mechanic characteristics of the aquifer. The studied area, into the municipality of Laterina (Arezzo, Italy), is a shallow basin filled by lacustrine and alluvial deposits (Pleistocene and Olocene epochs, Quaternary period), with alternated silt, sand with variable content of gravel and clay where the bottom is represented by arenaceous-pelitic rocks (Mt. Cervarola Unit, Tuscan Domain, Miocene epoch). This shallow basin constitutes the unconfined superficial aquifer to be exploited in the nearly future. To improve the geological model obtained from a detailed geological survey we performed electrical resistivity and P wave refraction tomographies along the same line in order to obtain different, independent and integrable data sets. For the seismic data also the reflected events have been processed, a remarkable contribution to draw the geologic setting. Through the k-means algorithm, we perform a cluster analysis for the bivariate data set to individuate relationships between the two sets of variables. This algorithm allows to individuate clusters with the aim of minimizing the dissimilarity within each cluster and maximizing it among different clusters of the bivariate data set. The optimal number of clusters "K", corresponding to the individuated geophysical facies, depends to the multivariate data set distribution and in this work is estimated with the Silhouettes. The result is an integrated tomography that shows a finite number of homogeneous geophysical facies, which therefore permits to distinguish and interpret the porous aquifer in a quantitative and objective way

Functional frontoparietal connectivity during short-term memory as revealed by high-resolution EEG coherence analysis

In this electroencephalographic study, the authors modeled the functional connectivity between frontal and parietal areas during short-term memory (STM) processes by spectral coherence analysis and the directed transfer function, that is, for the estimation of coherence "direction." A no-STM task was used as a reference. STM was characterized by an increased frontoparietal electroencephalograph coherence at high frequencies (beta and gamma, 14-45 Hz). In the control task, parietal-to-frontal flow prevailed at those frequencies. However, the STM task showed a bidirectional frontoparietal flow at the gamma band. In conclusion, frontoparietal connectivity would optimize "representational" memory during STM. In this context, the frontal areas would increase their influence on parietal areas for memory retention

TRACLAS: a project to improve under canopy tractor safety in case of overturning

Poster Abstract non previst

Familial adenomatous polyposis and inflammatory bowel disease associated in two kindreds

We describe two families in which some members are affected by familial polyposis syndrome: in one family a case of ulcerative colitis and in the other a case of Crohn's disease were found. This is the first report about this family association, but in our opinion the fact that two cases have been found in one series suggests that this association could be more frequent than reported so far. The research for a genetic pattern of inflammatory bowel disease could be addressed towards chromosome 5. © 1995 Plenum Publishing Corporation

Ricostruzione probabilistica 3D dell’acquifero alluvionale della Val di Cornia (Provincia di Livorno)

The three-dimensional alluvial aquifer reconstruction through deterministic method from well stratigraphical data is a well-known problem. The purpose of this study concerns the realization of a geostatistical stochastic model based on 1d Markov chains with the use of T-PROGS codes of GMS Aquaveo. This method allows to obtain the vertical transition probability of the alluvial deposits and propagate them to x-y plane through the application of Walther law. The Val di Cornia valley and San Vincenzo coastal plain constitute a unique multilayered coastal aquifer, which extends over an area of 170 square kilometers, in the southern coast of Tuscany (Italy), and it is the results of the erosional and depositional processes of the Cornia river. The better understanding of this aquifer is a crucial issue, due to its regional importance and for managing the increasing saltwater intrusion, which affects the area during the last 50 years. The model realization was initially based on 300 stratigraphic data logs coming from a water well database implemented by local authorities, subsequently integrated with HVSR data acquired for this work. The stratigraphic data were digitized and simplified in order to permit a better reconstruction. The control of the quality of the input data allowed to eliminate the stratigraphic logs that could be inconsistent with the surrounding ones, in order to avoid interpretation problems of the conceptual geological model. This filtering operation led, finally, to the selection of only 140 stratigraphic logs. The processing of this data allowed the reconstruction of the bottom of the model (the bedrock) and the realization of n-equiprobable simulations of the sedimentary hetereogeneity. The obtained geological model will allow the realization of further groundwater flow model of the Cornia Valley to be implemented in the next months

Human cortical rhythms during visual delayed choice reaction time tasks: A high-resolution EEG study on normal aging

Neuroimaging cognitive study of aging requires simple tasks ensuring a high rate of correct performances even in stressful neurophysiological settings. Here two simple delayed choice reaction time tasks were used to unveil event-related desynchronization (ERD) of theta (4-6 Hz) and alpha (6-12 Hz) electroencephalographic rhythms across normal aging. In the first condition, a cue stimulus (one bit) was memorized along a brief delay period (3.5-5.5 s). The explicit demand was visuo-spatial, but the retention could be also based on phonological and somatomotor coding. In the second condition, the cue stimulus remained available along the delay period. Correct performances were higher than 95% in both groups and tasks, although they were significantly better in young than elderly subjects (P<0.03). During the delay period, theta and alpha ERD accompanying correct responses were recognized in the two groups, the alpha ERD being stronger and prolonged during the memory than non-memory task. On the other hand, the fronto-parietal theta and parietal alpha ERD were stronger in young than elderly subjects during both tasks. Notably, the frontal alpha ERD was negligible in elderly subjects. In conclusion, the present simple tasks unveiled in elderly compared to young subjects (i) a weaker involvement of (para)hippocampal-cortical circuits as revealed by theta ERD and (ii) a weaker involvement of "executive" thalamo-cortical circuits as revealed by frontal alpha ERD. These effects might worsen behavioral performances to the simple cognitive tasks with age. The present protocol is promising for the neuroimaging study of pathological aging. © 2004 Elsevier B.V. All rights reserved

Human cortical EEG rhythms during long-term episodic memory task. A high-resolution EEG study of the HERA model

Many recent neuroimaging studies of episodic memory have indicated an asymmetry in prefrontal involvement, with the left prefrontal cortex more involved than the right in encoding, the right more than the left in retrieval (hemispheric encoding and retrieval asymmetry, or HERA model). In this electroencephalographic (EEG) high-resolution study, we studied brain rhythmicity during a visual episodic memory (recognition) task. The theta (4-6 Hz), alpha (6-12 Hz) and gamma (28-48 Hz) oscillations were investigated during a visuospatial long-term episodic memory task including an encoding (ENC) and retrieval (RET) phases. During the ENC phase, 25 figures representing interiors of buildings ("indoor") were randomly intermingled with 25 figures representing landscapes ("landscapes"). Subject's response was given at left ("indoor") or right ("landscapes") mouse button. During the RET phase (1 h later), 25 figures representing previously presented "indoor" pictures ("tests") were randomly intermingled with 25 figures representing novel "indoor" ("distractors"). Again, a mouse response was required. Theta and alpha EEG results showed no change of frontal rhythmicity. In contrast, the HERA prediction of asymmetry was fitted only by EEG gamma responses, but only in the posterior parietal areas. The ENC phase was associated with gamma EEG oscillations over left parietal cortex. Afterward, the RET phase was associated with gamma EEG oscillations predominantly over right parietal cortex. The predicted HERA asymmetry was thus observed in an unexpected location. This discrepancy may be due to the differential sensitivity of neuroimaging methods to selected components of cognitive processing. The strict relation between gamma response and perception suggests that retrieval processes of long-term memory deeply impinged upon sensory representation of the stored material. © 2004 Elsevier Inc. All rights reserved

Human cortical EEG rhythms during long-term episodic memory task. A high resolution EEG study of the HERA model.

Many recent neuroimaging studies of episodic memory have indicated an asymmetry in prefrontal involvement, with the left prefrontal cortex more involved than the right in encoding, the right more than the left in retrieval (hemispheric encoding and retrieval asymmetry, or HERA model). In this electroencephalographic (EEG) high-resolution study, we studied brain rhythmicity during a visual episodic memory (recognition) task. The theta (4– 6 Hz), alpha (6– 12 Hz) and gamma (28– 48 Hz) oscillations were investigated during a visuospatial longterm episodic memory task including an encoding (ENC) and retrieval (RET) phases. During the ENC phase, 25 figures representing interiors of buildings (‘‘indoor’’) were randomly intermingled with 25 figures representing landscapes (‘‘landscapes’’). Subject’s response was given at left (‘‘indoor’’) or right (‘‘landscapes’’) mouse button. During the RET phase (1 h later), 25 figures representing previously presented ‘‘indoor’’ pictures (‘‘tests’’) were randomly intermingled with 25 figures representing novel ‘‘indoor’’ (‘‘distractors’’). Again, a mouse response was required. Theta and alpha EEG results showed no change of frontal rhythmicity. In contrast, the HERA prediction of asymmetry was fitted only by EEG gamma responses, but only in the posterior parietal areas. The ENC phase was associated with gamma EEG oscillations over left parietal cortex. Afterward, the RET phase was associated with gamma EEG oscillations predominantly over right parietal cortex. The predicted HERA asymmetry was thus observed in an unexpected location. This discrepancy may be due to the differential sensitivity of neuroimaging methods to selected components of cognitive processing. The strict relation between gamma response and perception suggests that retrieval processes of long-term memory deeply impinged upon sensory representation of the stored material