We have observed a metallic solid (Al-14-at.%-Mn) with long-range orientational order, but with icosahedral point group symmetry, which is inconsistent with lattice translations. Its diffraction spots are as sharp as those of crystals but cannot be indexed to any Bravais lattice. The solid is metastable and forms from the melt by a first-order transition.

Metallic Phase with Long-Range Orientational Order and No Translational Symmetry

This review summarizes recent developments in the theory of spin glasses, as well as pertinent experimental data. The most characteristic properties of spin glass systems are described, and related phenomena in other glassy systems (dielectric and orientational glasses) are mentioned. The Edwards-Anderson model of spin glasses and its treatment within the replica method and mean-field theory are outlined, and concepts such as "frustration," "broken replica symmetry," "broken ergodicity," etc., are discussed. The dynamic approach to describing the spin glass transition is emphasized. Monte Carlo simulations of spin glasses and the insight gained by them are described. Other topics discussed include site-disorder models, phenomenological theories for the frozen phase and its excitations, phase diagrams in which spin glass order and ferromagnetism or antiferromagnetism compete, the Ne\'el model of superparamagnetism and related approaches, and possible connections between spin glasses and other topics in the theory of disordered condensed-matter systems.

Spin glasses: Experimental facts, theoretical concepts, and open questions

A high-intensity electron gun based on field emission from a film of aligned carbon nanotubes has been made. The gun consists of a nanotube film with a 1-millimeter-diameter grid about 20 micrometers above it. Field-emission current densities of about 0.1 milliampere per square centimeter were observed for applied voltages as low as 200 volts, and current densities greater than 100 milliamperes per square centimeter have been realized at 700 volts. The gun is air-stable, easy and inexpensive to fabricate, and functions stably and reliably for long times (short-term fluctuations are on the order of 10 percent). The entire gun is only about 0.2 millimeter thick and can be produced with virtually no restrictions on its area, from less than 1 square millimeter to hundreds of square centimeters, making it suitable for flat panel display applications.

http://science.sciencemag.org/content/sci/270/5239/1179.full.pdf

A Carbon Nanotube Field-Emission Electron Source

Bond-orientational order in molecular-dynamics simulations of supercooled liquids and in models of metallic glasses is studied. Quadratic and third-order invariants formed from bond spherical harmonics allow quantitative measures of cluster symmetries in these systems. A state with short-range translational order, but extended correlations in the orientations of particle clusters, starts to develop about 10% below the equilibrium melting temperature in a supercooled Lennard-Jones liquid. The order is predominantly icosahedral, although there is also a cubic component which we attribute to the periodic boundary conditions. Results are obtained for liquids cooled in an icosahedral pair potential as well. Only a modest amount of orientational order appears in a relaxed Finney dense-random-packing model. In contrast, we find essentially perfect icosahedral bond correlations in alternative "amorphon" cluster models of glass structure.

Bond-orientational order in liquids and glasses

PLUMED 2: New feathers for an old bird

Ising model on Penrose lattices : boundary conditions

The paper presents Porta-bile, a project under development in our University that intends to investigate the use of mobile computing technologies to support the learning processes in an educational context. The project focuses on the technological aspects of mobile learning, and on their integration with e-Learning systems, and more generally, with the information systems of the academic institutions. The project has its foundations in the availability of significant experience on e-learning real processes, and on the availability of the source code of an e-learning system developed in previous projects at the University of Trento and presently in production at the Economics school, and of the newer platform for the whole University of Trento that gathers the experience obtained in the past. 1. Introduction In this paper we will present Porta-bile, a portal for mobile learning that is under development at our University. The main goal of the project is to experiment m-learning technologies in real learning processes taking place at a University. The use of ICTs for learning has been studied in various ways, but in the recent years quick advance of mobile technologies a new term has appeared – mobile learning. Mobile learning is a field which combines two very promising areas – mobile computing and e-learning. Mobile learning is intended as any form of learning and teaching that use mobile devices (like cellular phones, Personal digital assistants (PDA), smart-phones, tablet PC etc.) in a mobile environment. On the other side of mobile learning, we have e-learning, i.e., every educational process assisted by computers through the use of networks, and Internet in particular. M-learning is often considered as the future of learning, or as an integral part of any other form of educational process in the future. A mobile learning educational process can be considered as any learning and teaching activity that is possible through mobile tools or in settings where mobile equipment is available. In the first part of this paper, we shall briefly overview the state of research in the m-learning field. In fact, ass m-learning is quite a new domain, there is a lot of work and research that is presently going on. People are trying to understand: • Which learning models can help obtaining better learning processes when communication is mediated by mobile devices, and how the student mobility affects her/his learning process . • How it is possible to evaluate efficiency and effectiveness of learning processes based upon mobile technologies, given the physical limitation of mobile devices. • Which services are useful for mobile devices, and which is the enabling technology that can affect the wide diffusion of mobile learning. In the second part of the paper we shall discuss our approach to the problem: we intend to develop methodologies and tools for the design, the analysis and the prototyping of services for mobile computing. The coupling of advanced technologies, like the ones involved in mobile computing, with learning and assessment models represents an advanced point of research. We will propose a system that will integrate a traditional Learning management system with extensions that allow to face with infomobility, thus allowing users of a LMS to interact with the other actors through the use of mobile devices. This integration will be realized with web services technology, in order to be free from platform, operating systems and development framework constraints. The objective will be pursued through: • Adoption of a well tested e -learning platform adapted to the usage of mobile devices • Implementation of mobile computing services by using widespread mobile devices, on the client side, and web services on the server side. • Study of learning models linked to mobile technologies, in order to understand in which way the use of limited devices impact the learning processes • Design and development of Learning Objects suited to mobile learning, together with services for evaluating their effectiveness • Experimentation of prototypes built in real learning processes Another interesting aspect of the project is the experimentation of the integration between the two most used development frameworks for web application available on the market today, i.e., SUN J2EE and Microsoft .NET. The core of the Learning management system is in fact built on J2EE and java-related technologies, while the mobile extensions will be built on .NET framework. The interaction between the two will be granted once again by web services technology. We want to deeply test the most branded advantage of the web services technology, i.e. interoperability between platforms.

Towards a Multi-Vendor Mobile Learning Management System

A common approach to the problem of predicting students' exam scores has been to base this prediction on the previous educational history of students. In this paper, we present a model that bases this prediction on students' performance on several tasks assigned throughout the duration of the course. In order to build our prediction model, we use data from a semi-automated peer-assessment system implemented in two undergraduate-level computer science courses, where students ask questions about topics discussed in class, answer questions from their peers, and rate answers provided by their peers. We then construct features that are used to build several multiple linear regression models. We use the Root Mean Squared Error (RMSE) of the prediction models to evaluate their performance. Our final model, which has recorded an RMSE of 2.93 for one course and 3.44 for another on predicting grades on a scale of 18 to 30, is built using 14 features that capture various activities of students. Our work has possible implications in the MOOC arena and in similar online course administration systems.

/pdf/predicting-students-final-exam-scores-from-their-course-1zt2iitkex.pdf

Predicting students' final exam scores from their course activities

In this article, we provide an overview of the emerging research area on Analytics and Video-Based Learning. Although there are many and diverse ways of designing learning videos, there is limited understanding of the efficacy and usefulness of each method. Therefore, we survey the state-of-the-art in the design, development and evaluation of open and video-based courses. The main objective is to highlight the importance and benefits of analytics and to support instructors with the appropriate resources for improving the use of their courses. This can be achieved by combining and analyzing learners' interactions with other available data obtained from learners, as such video analytics open new avenues for research on open and video-based courses. In addition to the guidelines for video-based analytics we have selected five indicative case-studies that provide in-depth analysis..

/pdf/video-based-learning-and-open-online-courses-3dmph92wgt.pdf

Video-Based Learning and Open Online Courses

Today's learning management systems offer little or no support to knowledge management. As a consequence, students do not get a comprehensive, overall view of what might be useful for their individual needs, and the e-learning potential is not fully exploited. We propose an architecture for overcoming the problem and making e-learning more effective. We also implemented part of the proposed architecture.

Marco Ronchetti

Papers

Ising model on Penrose lattices : boundary conditions

Towards a Multi-Vendor Mobile Learning Management System

Predicting students' final exam scores from their course activities

Video-Based Learning and Open Online Courses

Knowledge management in an e-learning system