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Unsupervised feature learning using self-organizing maps.
Get PDFIn recent years a great amount of research has focused on algorithms that learn features from unlabeled data. These approaches are known as feature learning or deep learning methods and have been successfully applied to classify scene images and recognize with high precision handwritten characters. In this thesis we show that a feature learning approach can be used to segment complex textures, a problem for a long time addressed proposing a large amount of handcrafted descriptors and local optimization strategies. We employ the SOM neural network for its ability to natively provide a set of topologically ordered features. These features allow us to obtain a highly accurate local description, even in areas characterized by a transition from one texture to another. We also show that a single feature learning unit can be combined with others in order to significantly improve the quality of the texture description and, consequently, reduce the segmentation errors. The results obtained prove that the proposed segmentation method is valid and provides a real alternative to other state-of-the-art methods. Since the proposed framework is simple, we easily combined it with a pyramidal histogram encoding and a SVM supervised network in order to classify scene images. We show that the important topological ordering property, inherited from the SOM network, allow us to resize the feature set, obtained during the initial unsupervised learning, avoiding an unpredictable performance loss. Moreover, the results on the standard Caltech-101 dataset prove a significant improvement on some state-of-the-art computer vision methods, designed specifically for image classification
Advanced security aspects on Industrial Control Network.
Get PDFSecurity threats are one of the main problems of this computer-based era. All systems making use of information and communication technologies (ICT) are prone to failures and vulnerabilities that can be exploited by malicious software and agents. In the latest years, Industrial Critical Installations started to use massively network interconnections as well, and what it is worst they came in contact with the public network, i.e. with Internet.
Industrial networks are responsible for process and manufacturing operations of almost every scale, and as a result the successful penetration of a control system network can be used to directly impact those processes. Consequences could potentially range from relatively benign disruptions, such as the disruption of the operation (taking a facility offline), the alteration of an operational process (changing the formula of a chemical process), all the way to deliberate acts of sabotage that are intended to cause harm.
The interconnectivity of Industrial Control Systems with corporate networks and the Internet has significantly increased the threats to critical infrastructure assets. Meanwhile, traditional IT security solutions such as firewalls, intrusion detection systems and antivirus software are relatively ineffective against attacks that specifically target vulnerabilities in SCADA protocols.
This presents presents an innovative approach to Intrusion Detection in SCADA systems based on the concept of Critical State Analysis and State Proximity. The theoretical framework is supported by tests conducted with an Intrusion Detection System prototype implementing the proposed detection approach
Hawking radiation and mode conversion at optically induced horizons.
Get PDFThe scattering of electromagnetic radiation is an essential and fundamental tool by which we may study light-matter interaction.
In usual conditions, the medium is considered as stationary and scattering is characterized by a change in the wavevector spectrum of the light beam. The frequency of the beam is not affected. In this thesis we study the problem of scattering from a moving dielectric perturbation (DP) induced by the nonlinear Kerr effect. Light is scattered and resonantly transferred to two output modes identified by distinct frequencies, one positive and the other negative in the comoving reference frame. Experiments confirm generation of negative resonant radiation in a variety of settings, ranging from optical fibers to bulk Kerr media. A first Born approximation analysis, verified by numerical simulations, predicts that the mixing of the positive and negative modes during the scattering process leads to amplification at the expense of the DP. This provides a link with the spontaneous emission of photons, known as “Hawking radiation”, excited at the event horizon of a gravitational black hole. The moving DP is thus described using the tools of transformation optics and general relativity, in terms of a flowing medium which curves the effective space-time metric as seen by the light rays. Our experimental results show evidences of spontaneous photon emission by the analogue horizon associated to the moving DP, which are in quantitative agreement with the Hawking model
β-glucuronidases in plants.
Get PDFIn the last decade, the interest for the presence and role of endogenous GUS in plants increased, being previously limited to the use of GUS from E. coli as a reporter gene. Three different GUS genes have been identified in A. thaliana and different roles have been suggested, mainly associated to plant cell wall remodelling and to the regulation of the presence in the active form of molecules with regulative functions.
This thesis investigated several aspects: A) artefacts in histochemical GUS detection, B) role of GUS in pollen tube germination and growth, C) GUS expression in N. tabacum and A. thaliana, D) identification of GUS genes in N. tabcum and their phylogenetic analysis in angiosperms.
A) Histochemical detection of E.coli GUS activity in transformed plants can be impaired by the presence of GUS inhibitors and by the solubility of an intermediate reaction product formed when X-glu is used as substrate. The expression of LAT52 has been revised.
B) The use of saccharolattone, a GUS inhibitor, suggests that GUS is involved in pollen tube germination and growth.
C) GUS expression was observed in all organs of N. tabacum and A. thaliana.
Expression studies, in collaboration with researchers of Calabria University, have been performed in Arabidopsis, by in situ mRNA hybridization: GUS3 is specifically expressed in border like cells and probably it is involved in their detachment from root tip; GUS1 and GUS2 are expressed in the root cup meristem, resulting perhaps involved in regulation of the mitotic cycle.
D) In N. tabacum GUS2 was completely sequenced and one GUS1 and two GUS3 have been partially sequenced. By bioinformatics analysis, GUS genes have been identified in other angiosperms species and a phylogenetic analysis have been conducted
Could Aeromonas spp. be considered a vector of resistance genes from the environment to human intestinal flora?
Get PDFAntibiotic resistant bacteria and antibiotic resistance genes cause increasing problems in clinical setting and are considered emerging environmental contaminants. In the environment, antibiotic resistant bacteria may be inactivated but their resistance determinants may become part of the environmental gene pool and may move back to human and animal intestinal flora via food and drinking water.
In order to assess the role of Aeromonas spp. in the flow of resistant determinants, we analyzed by resistance profiles, plasmidic and integrons content and characterization, 231 Aeromonas spp. and 250 Fecal Coliforms isolated from different aquatic environments. Resistance patterns could be related to both the presence of multiple plasmids and to the origin of the strains. The 31.7% of the plasmids carried by the Aeromonas strains were mobilizable as assess by dot-blot of MOB-subfamily covering the BHR (Broad Host Range) incompatibility groups. The majority (75%) of the Class 1 integrons were chromosomally locate and were found in the 27.7% of the Aeromonas spp. tested.
The number and type of resistance genes identified so far on Aeromonas spp. Support the hypothesis of considering these bacteria as a "reservoir" of resistance genes.
The capability of some Aeromonas strains to transfer their resistance to Fecal Coliform has been demonstrated, thus allowing to assert its role as a “vector” of resistance genes to members of the human intestinal flora
Properties of the insect neutral amino acis cotransporter KAAT1 studied by alanine scanning mutagenesis and temperature.
Get PDFThe possibility of heterologous expression in Xenopus laevis oocytes has greatly expanded the knowledge of the properties of several cotransporters, membrane proteins that, combining features of pumps and channels, couple the movement of ions and substrates. Transport across the membrane guarantees the reuptake of neurotransmitters from the synaptic cleft, the absorption of nutrients, the regulation of osmolarity and ionic homeostasis. Some of these proteins are involved in neurological diseases and in drug abuse. All the Na+/Cl--dependent cotransporters share high homology and possess the structural topology of the procariotic prototype transporter, LeuT. The present research work was focused on the insect neutral amino acid contransporter KAAT1 (K+-coupled Amino Acid Transporter 1), cloned from the midgut of the larva of Manduca sexta (Castagna et al., 1998;Feldman et al., 2000) and homologous with amino acid transporters belonging to the solute carrier 6 (SLC6) gene family.
The functional role of an highly conserved sequence, consisting of three consecutive glycines (Gly85-Gly86-Gly87), has been investigated by alanine scanning mutagenesis; this sequence is located in the first extracellular loop of the protein, close to Arginine 76, the residue that participates to the external gate of the protein.
The functional characteristics, i.e. transport activity, apparent affinity, interaction with different cations, were derived from electrophysiological measurements (TEVC, Two Electrode Voltage Clamp), and uptake experiments. Additional informations about the correct targeting to the plasma membrane of the glycine mutants have been obtained performing optical measurement of the surface expression by the single oocyte chemiluminescence (SOC) technique pioneered by Zerangue (Zerangue et al., 1999) and used by others (Haerteis et al., 2009;Bossi et al., 2011).
Changes in the transport mechanisms observed for many of the analyzed mutants, indicated a relevant role of the glycine triplet in the transport function, that it was confirmed by the alterations of the uncoupled currents and the apparent affinity.
The second part of my PhD work, covered the analysis of the relationship between temperature and substrate affinity in the ion-coupled cotransporter KAAT1 (from a poikilotherm invertebrate) in comparison with rGAT1, the GABA neuronal transporter originating from a mammalian (homeotherm) animal. Observations based on the rate of transport, and the effects on the presteady-state currents, i.e. the electrical signal arising from the initial steps of the transport cycle (Parent et al., 1992;Parent et al., 1992;Mager et al., 1998;Bossi et al., 1999a) were studied in order to evaluate the kinetic properties of the cotransport system at more physiological temperatures. A strong increase of transmembrane currents was measured in both transporters at higher temperature (30°C); the increased maximal transport-associated current (Imax) was counterbalanced by a lower apparent substrate affinity (K05). The inverse relationship between affinity and current supports previous observations in the intestinal tranporter PepT1(Bossi et al., 2012)
L’ombra di Polemos, i riflessi del Bios. La prospettiva della cura a partire da Jan Patočka e Michel Foucault.
Get PDFA partire dalle riflessioni del fenomenologo ceco Jan Patočka e dagli studi del filosofo francese Michel Foucault, questa ricerca intende esplorare il tema della cura – di sé, dell’anima, degli altri, del mondo – in quanto forma di relazione etica. Nell’eclissi dei sistemi valoriali tradizionali, le ricerche sulla nozione di cura possono offrire una prospettiva etica capace di riformulare i termini della responsabilità collettiva.
Il punto di partenza è un passaggio dell’ultimo corso di Foucault al Collège de France (Il coraggio della verità), dove il filosofo fa riferimento al pensiero di Patočka. Foucault riconosce all’autore ceco di essere stato il solo autore contemporaneo ad aver approfondito il principio antico dell’epimeleia. Tuttavia, secondo Foucault, la propria personale ricerca – articolata attorno alla nozione di epimeleia heautou, cioè di cura come messa alla prova, problematizzazione e stilizzazione di sé – differirebbe da quella di Patočka, più interessata allo studio dell’epimeleia tes psyches, ossia all’anima sotto il profilo ontologico e gnoseologico.
Innanzitutto, la tesi di Foucault incoraggia un’analisi del significato del termine “anima” nel contesto della fenomenologia asoggettiva elaborata da Patočka. In secondo luogo, invita a studiare la nozione di “sé” presente negli ultimi testi di Foucault.
Indagando i rapporti tra i processi singolari di soggettivazione e il bios in quanto “modo di vita” o “stile di esistenza”, si arriva a porre il problema della vita in quanto orizzonte ontologico dell’essere in comune. Ci si interroga così sulla possibilità di una cura del bios che sia insieme “legame di vita” e “modo di vita”: cura del bios come ontologia critica delle condizioni che rendono possibile il riconoscimento della vita, intesa come dimensione della coappartenenza, e allo stesso tempo attitudine etica a farsi carico della sua vulnerabilità
In vitro modulation of the microgual phenotype by physioological and pathological stimuli: perspectives for neuroinflammatory and neurodegenerative diseases.
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First insights on the signaling pathways related to CDKL5 regulation and on its possible involvement in synaptic plasticity
No full textRett syndrome (RTT) is an X-linked form of mental retardation that occurs sporadically once every 10,000-15,000 female births. After a period of normal development (6-18 months), the patients show a rapid regression of acquired speech and motor skills and the development of several symptoms including mental retardation, seizures, intermittent hyperventilation and stereotypic hand movements. This condition is mainly stable and signs of progressive neurodegeneration are absent. Almost 80% of Rett cases are associated with mutations in the
MECP2 (methyl CpG binding protein 2) gene. MeCP2 is a nuclear protein that binds methylated DNA and recruits histone deacetylases and co-repressor complexes to suppress transcription. It belongs to the MBD family of proteins involved in the epigenetic regulation of gene-expression.
Recently, mutations in the X-linked gene cyclin-dependent kinase-like 5 (CDKL5) have been found in patients characterized by a subset of Rett clinical phenotypes and generally suffering of infantile spasms and severe mental retardation. The product of CDKL5 is a serine/threonine kinase that belongs to the CMGC family; the exact functions exerted by this kinase and its regulatory mechanisms remain mainly unknown.
CDKL5 is present in the nucleus and in the cytosol of neurons and its expression shows a continued increase during development; accordingly, CDKL5 is a critical regulator of neuronal morphogenesis, neurite growth and dendritic arborization. In the cytosol, CDKL5 phosphorylates NGL-1 (Netrin-G1 Ligand 1), a regulator of early synapse formation and maturation. In the nucleus, CDKL5 binds and phosphorylates in vitro MeCP2. Furthermore, in the nucleus CDKL5 colocalizes with nuclear speckles and is probably involved in the regulation of mRNA splicing.
Recently our group has demonstrated that the expression levels and the subcellular distribution of CDKL5 are modified by neuronal activation. In particular, a glutamate bath induces in cultured hippocampal neurons the rapid exit of the kinase from the nucleus and its proteasome-dependent degradation. The significance of this response remains to be elucidated. Furthermore, BDNF induces in rat cortical cultures, a rapid phosphorylation of CDKL5.
The main aim of this work was to study how neuronal depolarization or activation by BDNF affects Cdkl5 regulation, in terms of gene transcription, post translation modifications of its final protein product and the involved signaling pathway(s). We found that, both in primary murine neuronal cultures and cortical slices, depolarization affects the expression of the gene, both at the transcriptional and post-transcriptional levels, together with its phosphorylation state. The response is affected by the maturation stage of the treated neurons and the involved signaling pathways have been characterized. We speculate that the observed regulation of Cdkl5 during neuronal depolarization could be related to a role of the kinase in neuronal activation. Electrophysiological approaches will be required to confirm the involvement of CDKL5 in the regulation of neuronal activity; furthermore, the identification of novel interactors of Cdkl5 should help in understanding its physiological functions in the central nervous system and the pathological consequences of a malfunctioning CDKL5