Functional derivatives of Tc for a two-band superconductor: application to MgB2

We address the question of how phonons of various frequencies contribute to the superconducting transition temperature $T_c$ of a multi-band superconductor by considering the functional derivatives of $T_c$ with respect to various intraband and interband electron-phonon coupling functions. A general scheme for computing such functional derivatives is developed. The proofs are given that the functional derivatives which are diagonal in band indices are linear in phonon energy $\Omega$ at small $\Omega$, while the functional derivatives which are off-diagonal in band indices diverge at $\Omega$ = 0 as 1/$\Omega$. The case of a two-band model for MgB$_{2}$ is treated numerically.Comment: 6 pages, 4 figure

English language knowledge of first-year university students on performance-based tests

Come espresso nelle linee guida del MIUR, gli obiettivi previsti nel curriculum di lingua straniera per gli studenti del 5° anno del liceo corrispondono al livello B2 del Quadro comune europeo di riferimento per la conoscenza delle lingue (QCER). In questo livello gli studenti dovrebbero dimostrare un accettabile livello di fluency linguistica. Questo articolo si occupa della capacità degli studenti del primo anno di università di saper utilizzare la propria competenza in lingua inglese nell’espletamento di compiti autentici. Il test costruito e somministrato valuta la conoscenza linguistica degli studenti a livello B2 mediante due compiti e scale di valutazione olistiche e analitiche basate sul Framework delle competenze linguistiche di Bachman e Palmer. Insieme al test è stato somministrato il questionario. Il risultato rivela che il 23% degli studenti che hanno completato il test soddisfano i requisiti del MIUR.As stated by the Guidelines of the Italian Ministry of Education, the aims and objectives of the fifth-year foreign language curriculum of lyceums correspond to the B2 level of the Common European Framework of Reference for languages (CEFR). At this level, students are expected to demonstrate an acceptable level of fluency in writing and speaking. This paper addresses the issue of the ability of first-year university students to employ their English language knowledge to perform authentic tasks, such as writing an enquiry email. The test designed and administered to gather data aims at evaluating student knowledge at a B2 level, by means of two tasks and holistic and analytic rating scales based on Bachman and Palmer’s framework of language competence. At the same time, a student questionnaire was administered. The results reveal that 23% of students who have completed the test meet the requirements of the Ministry of Education

Optimising ITS behaviour with Bayesian networks and decision theory

We propose and demonstrate a methodology for building tractable normative intelligent tutoring systems (ITSs). A normative ITS uses a Bayesian network for long-term student modelling and decision theory to select the next tutorial action. Because normative theories are a general framework for rational behaviour, they can be used to both define and apply learning theories in a rational, and therefore optimal, way. This contrasts to the more traditional approach of using an ad-hoc scheme to implement the learning theory. A key step of the methodology is the induction and the continual adaptation of the Bayesian network student model from student performance data, a step that is distinct from other recent Bayesian net approaches in which the network structure and probabilities are either chosen beforehand by an expert, or by efficiency considerations. The methodology is demonstrated by a description and evaluation of CAPIT, a normative constraint-based tutor for English capitalisation and punctuation. Our evaluation results show that a class using the full normative version of CAPIT learned the domain rules at a faster rate than the class that used a non-normative version of the same system