6809 research outputs found
Sort by
Caratteristiche strutturali delle associazioni fitoplanctoniche nel Lago Maggiore ed evoluzione stagionale dei popolamenti
Get PDFNot availableRicerche sull\u27evoluzione del Lago Maggiore. Aspetti limnologici. Programma triennale 2013-2015. Campagna 2014. Caratteristiche strutturali delle associazioni fitoplanctoniche nel Lago Maggiore ed evoluzione stagionale dei popolamenti. Struttura dei popolamenti fitoplanctonici e variazioni della biomassa algale
Solving complexes of cryptic species by using detailed analyses on jaw morphology in asexual rotifers
Get PDFJaws in rotifers, called trophi, are among the most important hard structure used for taxonomy and systematics. Selection on feeding ecology acts on these features and produced a wide array of shapes and adaptations, including filtering, piercing, grasping, pumping, etc. Bdelloid rotifers are completely asexual and morphological diversification in their trophi happened without the potentials offered by sexual recombination. I will review the approaches that have been used to couple studies on molecular evolution, mostly through phylogenetic approaches, and studies on morphological diversification of trophi, mostly through geometric morphometrics. Such studies cover both macroevolutionary scenarios and microevolutionary detailed analyses of differences between cryptic species and comparisons between populations. Evolution in the absence of sexual recombination in animals is an intriguing topic, and I will suggest further ways to use rotifer jaws as an invaluable window to explore evolutionary changes
Density-dependent effects as key drivers of intraspecific size structure of six abundant fish species in lakes across Europe
No full textLarge scale studies on individual size distribution of fish have primarily been done at community level, but little attention is paid at species level. We described fish size structure by using mean size, size diversity and the slope of linear size spectra of six common European fish species to compare whether these metrics responded to the same large-scale continental gradients. As predictors, we included several environmental variables and relative estimates of abundance (catch per unit effort) as indicator of density-dependent effects. We found differences in the strength of the main predictors of size structure between the six species, but the direction of the response was relatively similar and consistent for most of the size metrics. Temperature variations across Europe weakly induced the similar negative response to the size metrics for most species. However, we found an unexpectedly strong density dependence of size structure in all species, resulting in lower mean body size and size diversity and steeper size spectra slopes. This suggests that the density-dependent effect is so far an underestimated driver of fish size structure
Deeply divergent sympatric mitochondrial lineages of the earthworm Lumbricus rubellus are not reproductively isolated
Get PDFBackground: The accurate delimitation of species is essential to numerous areas of biological research. An unbiased assessment of the diversity, including the cryptic diversity, is of particular importance for the below ground fauna, a major component of global biodiversity. On the British Isles, the epigeic earthworm Lumbricus rubellus, which is a sentinel species in soil ecotoxicology, consists of two cryptic taxa that are differentiated in both the nuclear and the mitochondrial (mtDNA) genomes. Recently, several deeply divergent mtDNA lineages were detected in mainland Europe, but whether these earthworms also constitute cryptic species remains unclear. This information is important from an evolutionary perspective, but it is also essential for the interpretation and the design of ecotoxicological projects. In this study, we used genome-wide RADseq data to assess the reproductive isolation of the divergent mitochondrial lineages of L. rubellus that occur in sympatry in multiple localities in Central Europe. Results: We identified five divergent (up to 16 % net p-distance) mitochondrial lineages of L. rubellus in sympatry. Because the clustering of the RADseq data was according to the population of origin and not the mtDNA lineage, reproductive isolation among the mtDNA lineages was not likely. Although each population contained multiple mtDNA lineages, subdivisions within the populations were not observed for the nuclear genome. The lack of fixed differences and sharing of the overwhelming majority of nuclear polymorphisms between localities, indicated that the populations did not constitute allopatric species. The nucleotide diversity within the populations was high, 0.7-0.8 %. Conclusions: The deeply divergent mtDNA sympatric lineages of L. rubellus in Central Europe were not reproductively isolated groups. The earthworm L. rubellus, which is represented by several mtDNA lineages in continental Europe, apparently is a single highly polymorphic species rather than a complex of several cryptic species. This study demonstrated the critical importance of the use of multilocus nuclear data for the unbiased assessment of cryptic diversity and for the delimitation of species in soil invertebrates
THE BAVIECA OPEN-SOURCE SPEECH RECOGNITION SYSTEM EXPERIMENTS ON ADULT AND CHILDREN ITALIAN SPEECH
Get PDFIn this paper, we describe the adaptation of the new BAVIECA ASR engine to Italian. After a brief comparison with other similar systems, we give an overview of the BAVIECA Acoustic and Language Model (AM) training procedure, we describe the final test proce-dures and we end reporting the results obtained so far in some adults and children speech ASR experiments, comparing them with those previously obtained with different recogni-tion engines
Selection of cortical dynamics for motor behaviour by the basal ganglia
Get PDFThe basal ganglia and cortex are strongly implicated in the control of motor preparation and execution. Re-entrant loops between these two brain areas are thought to determine the selection of motor repertoires for instrumental action. The nature of neural encoding and processing in the motor cortex as well as the way in which selection by the basal ganglia acts on them is currently debated. The classic view of the motor cortex implementing a direct mapping of information from perception to muscular responses is challenged by proposals viewing it as a set of dynamical systems controlling muscles. Consequently, the common idea that a competition between relatively segregated cortico-striato-nigro-thalamo-cortical channels selects patterns of activity in the motor cortex is no more suf?cient to explain how action selection works. Here, we contribute to develop the dynamical view of the basal ganglia-cortical system by proposing a computational model in which a thalamo-cortical dynamical neural reservoir is modulated by disinhibitory selection of the basal ganglia guided by top-down information, so that it responds with different dynamics to the same bottom-up input. The model shows how different motor trajectories can so be produced by controlling the same set of joint actuators. Furthermore, the model shows how the basal ganglia might modulate cortical dynamics by preserving coarse-grained spatiotemporal information throughout cortico-cortical pathways
The relationship between specific Pavlovian instrumental transfer and instrumental reward probability
Get PDFGoal-directed behavior is influenced by environmental cues: in particular, cues associated with a reward can bias action choice toward actions directed to that same reward. This effect is studied experimentally as specific Pavlovian-instrumental transfer (specific PIT). We have investigated the hypothesis that cues associated to an outcome elicit specific PIT by rising the estimates of reward probability of actions associated to that same outcome. In other words, cues reduce the uncertainty on the efficacy of instrumental actions. We used a human PIT experimental paradigm to test the effects of two different instrumental contingencies: one group of participants had a 33% chance of being rewarded for each button press, while another had a 100% chance. The group trained with 33% reward probability showed a stronger PIT effect than the 100% group, in line with the hypothesis that Pavlovian cues linked to an outcome work by reducing the uncertainty of receiving it. The 100% group also showed a significant specific PIT effect, highlighting additional factors that could contribute to specific PIT beyond the instrumental training contingency. We hypothesize that the uncertainty about reward delivery due to testing in extinction might be one of these factors. These results add knowledge on how goal-directed behavior is influenced by the presence of environmental cues associated with a reward: such influence depends on the probability that we have to reach a reward, namely when there is less chance of getting a reward we are more influenced by cues associated with it, and vice versa
VAD in failing Fontan: simulations of ventricular, cavo-pulmonary and biventricular assistance in the case of systolic or diastolic ventricular dysfunction and in pulmonary vascular resistance increment.
No full textConsidering the lack of donors, ventricular assist devices (VADs) could be an alternative to heart transplantation for failing Fontan patients, in spite of the lack of experience and the complex anatomy and physiopathology of these patients. Considering the high number of variables that play an important role such as type of Fontan failure, type ofVADconnection, and setting (rightVAD[RVAD], left VAD [LVAD], or biventricular VAD [BIVAD]), a numerical model could be useful to support clinical decisions. The aim of this article is to develop and test a lumped parameter model of the cardiovascular system simulating and comparing the VAD effects on failing Fontan. Hemodynamic and echocardiographic data of 10 Fontan patients were used to simulate the baseline patients\u27 condition using a dedicated lumped parameter model. Starting from the simulated baseline and for each patient, a systolic dysfunction, a diastolic dysfunction, and an increment of the pulmonary vascular resistance were simulated. Then, for each patient and for each pathology, the RVAD, LVAD, and BIVAD implantations were simulated. The model can reproduce patients\u27 baseline well. In the case of systolic dysfunction, the LVAD unloads the single ventricle and increases the cardiac output (CO) (35%) and the arterial systemic pressure (Pas) (25%). With RVAD, a decrement of inferior vena cava pressure (Pvci) (39%) was observed with 34% increment of CO, but an increment of the single ventricle external work (SVEW). With the BIVAD, an increment of Pas (29%) and CO (37%) was observed. In the case of diastolic dysfunction, the LVAD increases CO (42%) and the RVAD decreases the Pvci, while both increase the SVEW. In the case of pulmonary vascular resistance increment, the highest CO (50%) and Pas (28%) increment is obtained with an RVAD with the highest decrement of Pvci (53%) and an increment of the SVEW but with the lowest VAD power consumption. The use of numerical models could be helpful in this innovative field to evaluate the effect of VAD implantation on Fontan patients to support patient and VAD type selection personalizing the assistance
Managing uncertainty in bidirectional model transformations
No full textIn Model-Driven Engineering bidirectionality in transformations is regarded as a key mechanism. Recent approaches to non-deterministic transformations have been proposed for dealing with non-bijectivity. Among them, the JTL language is based on a relational model transformation engine which restores consistency by returning all admissible models. This can be regarded as an uncertainty reducing process: the unknown uncertainty at design-time is translated into known uncertainty at run-time by generating multiple choices. Unfortunately, little changes in a model usually correspond to a combinatorial explosion of the solution space. In this paper, we propose to represent the multiple solutions in a intensional manner by adopting a model for uncertainty. The technique is applied to JTL demonstrating the advantages of the proposal
KPI Evaluation of the Business Process Execution through Event Monitoring Activity
No full textNowadays, more and more industrial organizations are using Business Process Model and Notation (BPMN) for process modeling. Data collected during business process execution are used for deriving the key performance indicators (KPI) that allow continuous tracking of the process behavior and measurement of process-specific goals. KPIs evaluation leverages on business process monitoring solutions that can be embedded into the BPM execution framework or integrated as additional facilities. This paper presents an integrated framework that allows modeling, execution and analysis of business process based on a flexible and adaptable monitoring infrastructure. The main advantage of the proposed approach is that it is independent from any specific business process modeling notation and execution engine and allows for the definition and evaluation of user-specific KPI measures. An example of implementation of the proposed execution and monitoring framework as well as its validation on a real case study in the learning domain are also presented