1,727,335 research outputs found
An Adaptive Probailistic Approach to Goal-Level Imitation Learning
Full text linkImitation learning has been recognized as a promising technique to teach robots advanced skills. It is based on the idea that robots could learn new behaviors by observ- ing and imitating the behaviors of other skilled actors. We propose an adaptive probabilistic graphical model which copes with three core issues of any imitative behavior: observation, representation and reproduction of skills. Our model, Growing Hierarchical Dynamic Bayesian Network (GHDBN), is hierarchi- cal (i.e. able to characterize structured behaviors at different levels of abstraction), and growing (i.e. skills are learned or updated incrementally - and at each level of abstraction - every time a new observation sequence is available). A GHDBN, once trained, is able to recognize skills being observed and to reproduce them by exploiting the generative power of the model. The system has been successfully tested in simulation, and initial tests have been conducted on a NAO humanoid robot platform
A Probalisitic Approach to Learning a Visually Grounded Language Model through Human-Robot Interaction
Full text linkLanguage is among the most fascinating and complex cognitive activities that develops rapidly since the early months of infants’ life. The aim of the present work is to provide a humanoid robot with cognitive, perceptual and motor skills fundamental for the acquisition of a rudimentary form of language. We present a novel probabilistic model, inspired by the findings in cognitive sciences, able to associate spoken words with their perceptually grounded meanings. The main focus is set on acquiring the meaning of various perceptual categories (e.g. red, blue, circle, above, etc.), rather than specific world entities (e.g. an apple, a toy, etc.). Our probabilistic model is based on a variant of multi-instance learning technique, and it enables a robotic platform to learn grounded meanings of adjective/noun terms. The systems could be used to understand and generate appropriate natural language descriptions of real objects in a scene, and it has been successfully tested on the NAO humanoid robotic platform
Use of Clavien-Dindo classification in urology part 2 – upper tract
No full textA classification system of surgical complications was proposed by Clavien in 1992 [1] and further modified by Dindo in 2004 [2]. Clavien-Dindo classification has since then been validated through many retrospective case series as well as in comparative studies to standardise the complications and find out the superiority of one or other mode of treatment for a particular urological condition
"Psofo, Nananana e i loro amici - Storie d'insetti": laboratori didattici
No full textI laboratori sono stati organizzati in data 14 aprile 2007 e 21 aprile 2007 nell'ambito dell'iniziativa "Fieri di leggere", promossa dal Comune e dalla Provincia di Bologna, insieme alla Regione Emilia Romagna e alla Fiera del libro per ragazzi, allo scopo di tenere in comunicazione i ragazzi e il libro: chi lo immagina e lo crea, chi lo illustra, chi lo produce, lo diffonde e lo conserva proprio per i piccoli lettori. I due laboratori erano finalizzati ad avvicinare i ragazzi al mondo degli insetti attraverso due diversi momenti: 1) la presentazione e la lettura di brani tratti dal libro "Psofo, Nananana e i loro amici, Storie d'insetti ( a cui è allegato l'inserto "E per i grandi...i concetti fondamentali di entomologia") edito da Alberto Perdisa Editore, di cui Maria Luisa Dindo è co-autrice e 2) l'esposizione e di insetti vivi forniti da Gianumberto Accinelli, di EUGEA srl. EUGEA (Ecologia Urbana Giardini e Ambiente) è uno spin-off nato da un gruppo di ricercatori dell'area Entomologia del Dipartimento di Scienze e Tacnologie Agroambientali dell'Università di Bologna e ha l'obiettivo di riportare la natura e la sua preziosa bellezza in città (http:// www.eugea.it
Insetti esotici invasivi in Italia.Due specie di origine asiatica:il cinipede galligeno del castagno e la cimice asiatica
No full textLo spostamento di insetti da un Paese all’altro si verifica da secoli, ma è aumentato notevolmente a partire dalla scoperta dell’America e delle nuove rotte oceaniche verso l’Asia (tra il XV e il XVI secolo). Ultimamente, la globalizzazione e i cambiamenti climatici stanno fortemente incrementando questo processo. Viene illustrato come le specie esotiche arrivano, talvolta stabilizzandosi diventando “invasive”, e alcune strategie per cercare di arginare il fenomeno. Come casi studio, vengono considerati due insetti invasivi giunti dall’Estremo Oriente: il cinipide galligeno del castagno e la cimice asiatica
RG <i>vs.</i> LG: a) Clavien-Dindo grade I and II; b) Clavien-Dindo grade III; c) Clavien-Dindo grade IV; d) Clavien-Dindo grade V.
No full text<p>RG <i>vs.</i> LG: a) Clavien-Dindo grade I and II; b) Clavien-Dindo grade III; c) Clavien-Dindo grade IV; d) Clavien-Dindo grade V.</p
Tachinid parasitoids: are they to be considered as koinobionts?
No full textTachinids are usually considered as koinobionts as none of them kills or paralyzes the host when first entering it. These parasitoids, however, do not fill well into the koinobiont/idiobiont dichotomy because only some species show a high degree of physiological adaptation to the host, whereas the larvae of other species grow quickly following attack and kill the host rapidly, thus behaving more as idiobionts. The in vitro rearing technique provides further evidence for the poor adequacy of the koinobiont/idiobiont dichotomy for tachinids. In fact, while typical koinobionts are known to be difficult to culture on artificial media, some tachinids displaying non-synchronized development with the host have been successfully reared in vitro on insect material-free artificial media, thus behaving similarly to idiobionts. I therefore suggest not to use the koinobiont/idiobiont classification for tachinids and to class them instead only on the basis of the presence or absence of developmental synchrony with their host
Molecular analysis of the dimerization and aggregation processes of human alanine:glyoxylate aminotransferase and effect of mutations leading to Primary Hyperoxaluria Type I
Full text linkPrimary Hyperoxaluria Type 1 (PH1) is a rare autosomal recessive disorder characterized by the deposition of insoluble calcium oxalate crystals at first in the kidneys and urinary tract and then in the whole body. PH1 is caused by the deficiency of human liver peroxisomal alanine:glyoxylate aminotransferase (AGT). AGT is a pyridoxal 5'-phosphate (PLP)-dependent enzyme, which converts glyoxylate to glycine, thus preventing glyoxylate oxidation to oxalate and calcium oxalate formation. Only two curative therapeutic approaches are currently available for PH1: the administration of pyridoxine (PN), a precursor of PLP, which is only effective in a minority of patients (25- 35%), and liver transplantation, a very invasive procedure. AGT is encoded by the AGXT gene, which is present in humans as two polymorphic forms: the major allele (encoding AGT-Ma) and the minor allele (encoding AGT-Mi). PH1 is a very heterogeneous disease with respect to the clinical manifestations, the response to treatment and the pathogenic mechanisms. In fact, more than 200 pathogenic mutations have been identified so far and the molecular mechanisms by which missense mutations cause AGT deficiency span from functional, to structural and to subcellular localization defects or to a combination of them. Several lines of evidence at both molecular and cellular level, indicate that many disease-causing missense mutations interfere with AGT dimer stability and/or aggregation propensity. However, neither the dimerization nor the aggregation process of AGT have been analyzed in detail. Therefore, we engineered a mutant form of AGT stable in solution in the monomeric form and studied its biochemical properties and dimerization kinetics. We found that monomeric AGT is able to bind PLP and that the coenzyme stabilizes the dimeric structure. Moreover, the identification of key dimerization hot-spots at the monomer-monomer interface allowed us to unravel the mechanisms at the basis of the aberrant mitochondrial mistargeting of two of the most common PH1-causing variants. We also elucidated the molecular and cellular consequences of the pathogenic mutations R36H, G42E, I56N, G63R and G216R, involving residues located at the dimer interface, and tested their in-vitro responsiveness to the treatment with PN. The latter results allowed us to suggest a possible correlation between the structural defect of a variant and its degree of responsiveness to PN. Finally, by combining bioinformatic and biochemical approaches, we analyzed in detail the tendency of AGT to undergo an electrostatically-driven aggregation. We found that the polymorphic changes typical of the minor allele have opposite effect on the aggregation propensity of the protein, and we predicted the possible effect/s of pathogenic mutations of residues located on the AGT surface. Overall, the results obtained allow not only to better understand PH1 pathogenesis, but also to predict the response of the patients to the available therapies as well as to pave the way for the development of new therapeutic strategies
Evolution and market behavior with endogenous investment rules
Full text linkIn a complete market for short-lived assets, we investigate long run wealth-driven selection on a general class of investment rules that depend on endogenously determined current and past prices. We find that market instability, leading to asset mis-pricing and informational efficiencies, is a common phenomenon and is due to two different mechanisms. First, conditioning investment decisions on asset prices implies that dominance of an investment rule on others, as measured by the relative entropy, can be different at different prevailing prices thus reducing the global selective capability of the market. Second, the feedback existing between past realized prices and current investment decisions can lead to a form of deterministic overshooting. By investigating the random dynamical system that describes the price and wealth dynamics, we are able to derive general conditions for the occurrence of each type of market instability and the emergence of informational inefficiencies
Survival in Speculative Markets
Full text linkIn this paper, I consider an exchange economy with complete markets where agents have heterogeneous beliefs and, possibly, preferences, and investigate the Market Selection Hypothesis that speculation rewards the agent with the most accurate beliefs. First, on the methodological level, I derive the relative consumption dynamics as a function of agents’ effective discount factors, related to consumption decisions across time, and agents’ effective beliefs, related to consumption decisions across states. Sufficient conditions for agents’ survival, either in isolation or in a group, depend on the relative size of effective discount factors and on the relative accuracy of effective beliefs. Then, I show that in economies where agents maximize an Epstein-Zin utility the Market Selection Hypothesis fails: there exist parametrizations where the agent with correct beliefs vanishes and parametrizations where beliefs heterogeneity persists in the long run. Results are robust to local changes of beliefs, risk preferences, and the aggregate endowment process. These failures are shown not to occur when agents’ Epstein-Zin utility has a subjective expected utility representation due to an interdependence of effective discount factors and effective beliefs
- …
