Search results for " Informatica"
showing 10 items of 978 documents
U-search: a meta engine for creation of knowledge paths on the web
2010
The main tools used to find digital contents in the Web are search engines and directories but they are not presently able to understand the user specific needs and starting knowledge. This work presents "U-Search" a new meta engine that allows to create knowledge paths on the Web based on specific user requirements and knowledge levels. To this end, we consider different searcher categories such as a "basic searcher" who knows little about a topic and will look for more information, a "deep searcher" who will look for specific details on a topic that he/she already knows and a "wide searcher" who will look for expanding his/her knowledge domain with topics that are loosely related to the s…
A web search methodology for different user typologies
2009
Search engines and directories are the main tools used to find desired information into the ocean of digital contents that is the Web. However, they are not presently able to understand the user specific needs and starting knowledge because their inability to simulate the processes of human mind. Natural Language Processing, Folksonomy, Semantic Web and Serendipitous Surfing are some of the recent research fields towards understanding of human natural language and in general of real user needs. This work aims to add one step more to this evolution path by presenting a new search methodology that allows users to create new knowledge paths on the web based on their specific requirements. Thus…
Information transfer and information modification to identify the structure of cardiovascular and cardiorespiratory networks
2017
To fully elucidate the complex physiological mechanisms underlying the short-term autonomic regulation of heart period (H), systolic and diastolic arterial pressure (S, D) and respiratory (R) variability, the joint dynamics of these variables need to be explored using multivariate time series analysis. This study proposes the utilization of information-theoretic measures to measure causal interactions between nodes of the cardiovascular/cardiorespiratory network and to assess the nature (synergistic or redundant) of these directed interactions. Indexes of information transfer and information modification are extracted from the H, S, D and R series measured from healthy subjects in a resting…
NeXt for neuro-radiosurgery: A fully automatic approach for necrosis extraction in brain tumor MRI using an unsupervised machine learning technique
2017
Stereotactic neuro-radiosurgery is a well-established therapy for intracranial diseases, especially brain metastases and highly invasive cancers that are difficult to treat with conventional surgery or radiotherapy. Nowadays, magnetic resonance imaging (MRI) is the most used modality in radiation therapy for soft-tissue anatomical districts, allowing for an accurate gross tumor volume (GTV) segmentation. Investigating also necrotic material within the whole tumor has significant clinical value in treatment planning and cancer progression assessment. These pathological necrotic regions are generally characterized by hypoxia, which is implicated in several aspects of tumor development and gro…
Investigating cardiovascular and cerebrovascular variability in postural syncope by means of extended Granger causality
2014
The patterns of Granger causality (GC) between heart period (HP), mean arterial pressure (AP) and cerebral blood flow velocity (FV) were investigated in ten subjects with postural related syncope (PRS). The classic GC measure based on vector autoregressive (VAR) modeling was compared with a novel extended GC (eGC) measure derived from VAR models incorporating instantaneous causal effects among the series. The analysis was performed in the supine and in the upright position during early (ET) and late (LT, close to presyncope) epochs of head-up tilt. Moving from ET to LT, both GC and eGC decreased from AP to HP, and increased from AP to FV, reflecting baroreflex impairment and loss of cerebra…
Impact of Nonstationarities on Short Heart Rate Variability Recordings During Obstructive Sleep Apnea
2017
Obstructive sleep apnea (OSA) is a sleep disorder characterized by breathing pauses due to collapse of the upper airways. During OSA the autonomic modulation, as noninvasively assessed through heart period (HP) variability, is altered in a time-varying way even though time-varying properties of HP fluctuations are often disregarded by HP variability studies. We performed a time domain analysis computed over very short epochs corresponding to the sole OSA events explicitly accounting for HP variability nonstationarities. Length-matched epochs were extracted during OSA and quiet sleep (SLEEP) in 13 subjects suffering from OSA (11 males, age 55±11, apnea-hypopnea index 44±19). Mean HP, varianc…
Causal analysis of short-term cardiovascular variability: state-dependent contribution of feedback and feedforward mechanisms.
2016
Baroreflex function is usually assessed from spontaneous oscillations of blood pressure (BP) and cardiac RR interval assuming a unidirectional influence from BP to RR. However, the interaction of BP and RR is bidirectionalâRR also influences BP. Novel methods based on the concept of Granger causality were recently developed for separate analysis of feedback (baroreflex) and feedforward (mechanical) interactions between RR and BP. We aimed at assessing the proportion of the two causal directions of the interactions between RR and systolic BP (SBP) oscillations during various conditions, and at comparing causality measures from SBP to RR with baroreflex gain indexes. Arterial BP and ECG sig…
Role of causality in the evaluation of coherence and transfer function between heart period and systolic pressure in humans
2004
To elicit the effects of considering causality in the study of the interactions between RR interval and systolic pressure (SP) variability, the traditional noncausal cross-spectral analysis was compared with a causal method able to separate the two arms of the RR-SP regulatory loop. Estimates of coherence (K) and causal coherences from SP to RR (Ksr) and from RR to SP (Krs), and of noncausal (G) and causal (Gsr) baroreflex gain were evaluated at 0.1 Hz in 10 healthy young subjects in the supine position and after head-up tilt. While K was high in both conditions, at rest Ksr was significantly lower than Krs. After tilt, Ksr increased and Krs decreased significantly. With respect to G, Gsr w…
Information domain approach to the investigation of cardio-vascular, cardio-pulmonary, and vasculo-pulmonary causal couplings
2011
The physiological mechanisms related to cardio-vascular (CV), cardio-pulmonary (CP), and vasculo-pulmonary (VP) regulation may be probed through multivariate time series analysis tools. This study applied an information domain approach for the evaluation of non-linear causality to the beat-to-beat variability series of heart period (t), systolic arterial pressure (s), and respiration (r) measured during tilt testing and paced breathing (PB) protocols. The approach quantifies the causal coupling from the series i to the series j (C(ij)) as the amount of information flowing from i to j. A measure of directionality is also obtained as the difference between two reciprocal causal couplings (D(i…
An automatic system for helping health consumers to understand medical texts
2015
Medical texts (reports, articles, etc.) are usually written by professionals (physicians, medical researchers, etc.) who use their own language and communication style. On the other hand, these texts are often read by health consumers (as in the case of medical reports) who do not have the same skills and vocabularies of the experts and can have difficulties in text comprehension. To help a health consumer in understanding a medical text, it would be desirable to have an automatic system that, given a text written with medical (technical) terms, translates them in simple or plain language and provides additional information with the same kind of language. We have designed such a system. It …