Teaching and learning in information retrieval

A literature review of pedagogical methods for teaching and learning information retrieval is presented. From the analysis of the literature a taxonomy was built and it is used to structure the paper. Information Retrieval (IR) is presented from different points of view: technical levels, educational goals, teaching and learning methods, assessment and curricula. The review is organized around two levels of abstraction which form a taxonomy that deals with the different aspects of pedagogy as applied to information retrieval. The first level looks at the technical level of delivering information retrieval concepts, and at the educational goals as articulated by the two main subject domains where IR is delivered: computer science (CS) and library and information science (LIS). The second level focuses on pedagogical issues, such as teaching and learning methods, delivery modes (classroom, online or e-learning), use of IR systems for teaching, assessment and feedback, and curricula design. The survey, and its bibliography, provides an overview of the pedagogical research carried out in the field of IR. It also provides a guide for educators on approaches that can be applied to improving the student learning experiences

DY determinants, possibly associated with novel class II molecules, stimulate autoreactive CD4+ T cells with suppressive activity

A set of T cell clones (TCC) isolated from HLA-DR-, Dw-, DQ-matched allogeneic MLCs was found to proliferate autonomously when stimulated with cells carrying a wide range of class I or II specificities. This apparently unrestricted proliferation was relatively weak, and only low levels of IL-2 were present in the supernatants of stimulated cells. Autologous as well as allogeneic PBMC and B lymphoblastoid cell lines (B-LCL) were capable of stimulating such clones, which were also restimulated by suppressive, but not by helper, TCC. Moreover, such clones displayed the unusual property of autostimulation. mAb inhibition experiments suggested that class II- or class II-restricted antigens were involved in stimulation. Thus, certain "broad" mAbs (TU39, SG520) reacting with multiple locus products inhibited activation of these reagents, but none of those reacting more specifically with DR (TU34, TU37, L243, Q2/70, SG157), DQ (TU22, SPV- L3, Leu 10), or DP (B7/21), or mixtures of these mAbs, were able to do so. Evidence from sequential immunoprecipitation experiments suggested that mAb TU39 bound class II-like molecules other than DR, DQ, and DP on TCC and B-LCL, and it is therefore proposed that such putative novel class II-like molecules may carry the stimulating determinants for these autoreactive clones. DY-reactive clones lacked helper activity for B cells but mediated potent suppressive activity on T cell proliferative responses that was not restricted by the HLA type of the responding cells. Suppressive activity was induced in normal PBMC by such clones, as well as by independent suppressive clones, which was also inhibited only by mAb TU39. These findings lead to the proposal that DY-reactive autostimulatory cells may constitute a self- maintaining suppressive circuit, the level of activity of which would be regulated primarily by the availability of IL-2 in the microenvironmen

ϕ\phi meson transparency in nuclei from ϕN\phi N resonant interactions

We investigate the $\phi$ meson nuclear transparency using some recent theoretical developments on the $\phi$ in medium self-energy. The inclusion of direct resonant $\phi N$-scattering and the kaon decay mechanisms leads to a $\phi$ width much larger than in most previous theoretical approaches. The model has been confronted with photoproduction data from CLAS and LEPS and the recent proton induced $\phi$ production from COSY finding an overall good agreement. The results support the need of a quite large direct $\phi N$-scattering contribution to the self-energy

Thermodynamics of proton transfer reactions in the gas phase

This work is a study of proton transfer equilibria, with temperature dependence, in binary mixtures containing benzene, mono and disubstituted benzenes, using High Pressure Pulsed Electron Beam Source Mass Spectrometry. The measurements of equilibrium constants with temperature variation led to the determination of thermodynamic properties such as relative proton affinities (PAs), gas phase basicities (GBs) and entropy changes. It was also intended to infer the sites for proton attachment in the species under study through the entropy changes. For Proton Transfer Reactions it is generally accepted that the main contribution to the entropy changes arises from rotational symmetry changes which depend upon the protonation site. They are, therefore, usually very small. The existence of isomeric species can give rise to another entropy contribution designated as entropy of mixing which is, in most cases in proton transfer reactions, also very small. The sum of both contributions for the systems under study was in general expected to be less than 13 Jmol ¹K ˉ ¹. The ΔS° experimentally determined were found to be, for some systems, much higher (60Jmol ¹K ˉ ¹) than expected on the grounds of the classical contributions. Confirmation for these values was sought from ab initio calculations which were carried out at 4-31G basis set level. The conclusions drawn from this study indicate that a novel contribution to entropy changes must be taken into account in aromatics protonating on the ring if various adjacent sites are equally favoured for proton attachment. This is considered to be an internal translational contribution due to proton migration which is supposed to produce a dynamic structure for those protonated compounds. Substituted benzenes where, this contribution does not occur, seem to have a structure similar to the benzenium ion

Airy functions over local fields

Airy integrals are very classical but in recent years they have been generalized to higher dimensions and these generalizations have proved to be very useful in studying the topology of the moduli spaces of curves. We study a natural generalization of these integrals when the ground field is a non-archimedean local field such as the field of p-adic numbers. We prove that the p-adic Airy integrals are locally constant functions of moderate growth and present evidence that the Airy integrals associated to compact p-adic Lie groups also have these properties.Comment: Minor change

Survival probabilities in time-dependent random walks

We analyze the dynamics of random walks in which the jumping probabilities are periodic {\it time-dependent} functions. In particular, we determine the survival probability of biased walkers who are drifted towards an absorbing boundary. The typical life-time of the walkers is found to decrease with an increment of the oscillation amplitude of the jumping probabilities. We discuss the applicability of the results in the context of complex adaptive systems.Comment: 4 pages, 3 figure