Riccardo Rizzo

The dynamics of engineered resident proteins in the mammalian Golgi complex relies on cisternal maturation

Engineered Golgi-resident constructs that can be polymerized at will to prevent their recycling via Golgi carriers provide evidence for the cisternal maturation mechanism of secretory protein transport through the Golgi.

Map-based horizontal navigation in educational Hypertext

This paper discusses the problem of horizontal (non-hierarchical) navigation in modern educational courseware. We will look at why horizontal links disappear, how to support horizontal navigation in modern hyper-courseware, and our earlier attempts to provide horizontal navigation in Web-based electronic textbooks. Here, we present map-based navigation - a new approach to support horizontal navigation in open corpus educational courseware that we are currently investigating. We will describe the mechanism behind this approach, present a system KnowledgeSea that implements this approach, and provide some results of a classroom study of this system.

Control Systems of Membrane Transport at the Interface between the Endoplasmic Reticulum and the Golgi

A fundamental property of cellular processes is to maintain homeostasis despite varying internal and external conditions. Within the membrane transport apparatus, variations in membrane fluxes from the endoplasmic reticulum (ER) to the Golgi complex are balanced by opposite fluxes from the Golgi to the ER to maintain homeostasis between the two organelles. Here we describe a molecular device that balances transport fluxes by integrating transduction cascades with the transport machinery. Specifically, ER-to-Golgi transport activates the KDEL receptor at the Golgi, which triggers a cascade that involves Gs and adenylyl cyclase and phosphodiesterase isoforms and then PKA activation and results in the phosphorylation of transport machinery proteins. This induces retrograde traffic to the ER and balances transport fluxes between the ER and Golgi. Moreover, the KDEL receptor activates CREB1 and other transcription factors that upregulate transport-related genes. Thus, a Golgi-based control system maintains transport homeostasis through both signaling and transcriptional networks.

Transport of soluble proteins through the Golgi occurs by diffusion via continuities across cisternae

The mechanism of transport through the Golgi complex is not completely understood, insofar as no single transport mechanism appears to account for all of the observations. Here, we compare the transport of soluble secretory proteins (albumin and α1-antitrypsin) with that of supramolecular cargoes (e.g., procollagen) that are proposed to traverse the Golgi by compartment progression–maturation. We show that these soluble proteins traverse the Golgi much faster than procollagen while moving through the same stack. Moreover, we present kinetic and morphological observations that indicate that albumin transport occurs by diffusion via intercisternal continuities. These data provide evidence for a transport mechanism that applies to a major class of secretory proteins and indicate the co-existence of multiple intra-Golgi trafficking modes. DOI: http://dx.doi.org/10.7554/eLife.02009.001

A KST-BASED SYSTEM FOR STUDENT TUTORING

A novel assessment procedure based on knowledge space theory (KST) is presented along with a complete implementation of an intelligent tutoring system (ITS) that has been used to test our theoretical findings. The key idea is that correct assessment of the student knowledge is strictly related to the structure of the domain ontology. Suitable relationships between the concepts must be present to allow the creation of a reverse path from the “knowledge state” representing the student goal to the one that contains her actual knowledge about this topic. Knowledge space theory is a very good framework to guide the process of building the ontology used by the artificial tutor. The system we present uses a conversational agent to assess the student knowledge through a natural language question/answer procedure. The system exploits a Cyc-based common sense ontology about the specific domain of interest to select the concepts needed to explain unknown topics emerging from the dialogue. Besides, the latent semantic analysis (LSA) technique is used to determine the correctness of the student sentences in order to establish which concepts she knows. As a result, the system supplies learning material arranged as a path between the unknown topics resulting from the student assessment. The learning path is presented to the student by a user-friendly graphical interface, which allows to access documents browsing a visual map. The procedure is explained in detail along with the rest of the system, and the assessment validation results are presented.

Using maps and landmarks for navigation between closed and open corpus hyperspace in Web-based education

Abstract This paper focuses on the problem of building links from closed to open corpus Web pages in the context of Web-based education. As a possible solution it introduces land mark-based navigation using semantic information space maps - an approach that we are currently investigating. The technical part of the paper presents a system Knowledge Sea that implements this approach, describes the mechanism behind the system, and reports some results of a classroom evaluation of this system.

A Framework for Sign Language Sentence Recognition by Commonsense Context

This correspondence proposes a complete framework for sign language recognition that integrates a commonsense engine in order to deal with sentence recognition. The proposed system is based on a multilevel architecture that allows modeling and managing of the knowledge of the recognition process in a simple and robust way. The final abstraction level of this architecture introduces the semantic context and the analysis of the correctness of a sentence given in a sequence of recognized signs. Experimentations are presented using a set of signs from the Italian sign language (LIS) for domotic applications. The implemented system maintains a high recognition rate when the set of signs grows, correcting erroneously recognized single signs using the sentence context.

Experiences with cicerobot, a museum guide cognitive robot

The paper describes CiceRobot, a robot based on a cognitive architecture for robot vision and action. The aim of the architecture is to integrate visual perception and actions with knowledge representation, in order to let the robot to generate a deep inner understanding of its environment. The principled integration of perception, action and of symbolic knowledge is based on the introduction of an intermediate representation based on Gardenfors conceptual spaces. The architecture has been tested on a RWI B21 autonomous robot on tasks related with guided tours in the Archaeological Museum of Agrigento. Experimental results are presented.

I Feel Blue: Robots and Humans Sharing Color Representation for Emotional Cognitive Interaction

The paper presents a representation of colors integrated in a cognitive architecture inspired by the Psi model. In the architecture designed for a humanoid robot, the observation and recognition of humans and objects influence the emotional state of the robot. The representation of color is an additional feature that allows the robot to be “in tune” with the humans and share with them a physical space and interactions. This representation takes into account the current hypothesis about how the human brain allows sophisticated process and manage the colors, considering both universals and linguistic approaches. The paper describes in detail the problems of color representation, the potential of a cognitive architecture able to associate them with emotions, and how they can influence the interactions with the human.

A comparison between habituation and conscience mechanism in self-organizing maps

In this letter, a preliminary study of habituation in self-organizing networks is reported. The habituation model implemented allows us to obtain a faster learning process and better clustering performances. The habituable neuron is a generalization of the typical neuron and can be used in many self-organizing network models. The habituation mechanism is implemented in a SOM and the clustering performances of the network are compared to the conscience learning mechanism that follows roughly the same principle but is less sophisticated