A homotopy double groupoid of a Hausdorff space II: a van Kampen theorem

This paper is the second in a series exploring the properties of a functor which assigns a homotopy double groupoid with connections to a Hausdorff space. We show that this functor satisfies a version of the van Kampen theorem, and so is a suitable tool for nonabelian, 2-dimensional, local-to-global problems. The methods are analogous to those developed by Brown and Higgins for similar theorems for other higher homotopy groupoids. An integral part of the proof is a detailed discussion of commutative cubes in a double category with connections, and a proof of the key result that any composition of commutative cubes is commutative. These results have recently been generalised to all dimensions by Philip Higgins.Comment: 19 pages, uses picte

Modifiability of the psychomotor domain

Bibliography: p. 194-225

The promoter of the human interleukin-2 gene contains two octamer-binding sites and is partially activated by the expression of Oct-2

The gene encoding interleukin-2 (IL-2) contains a sequence 52 to 326 nucleotides upstream of its transcriptional initiation site that promotes transcription in T cells that have been activated by costimulation with tetradecanoyl phorbol myristyl acetate (TPA) and phytohemagglutinin (PHA). We found that the ubiquitous transcription factor, Oct-1, bound to two previously identified motifs within the human IL-2 enhancer, centered at nucleotides -74 and -251. Each site in the IL-2 enhancer that bound Oct-1 in vitro was also required to achieve a maximal transcriptional response to TPA plus PHA in vivo. Point mutations within either the proximal or distal octamer sequences reduced the response of the enhancer to activation by 54 and 34%, respectively. Because the murine T-cell line EL4 constitutively expresses Oct-2 and requires only TPA to induce transcription of the IL-2 gene, the effect of Oct-2 expression on activation of the IL-2 promoter in Jurkat T cells was determined. Expression of Oct-2 potentiated transcription 13-fold in response to TPA plus PHA and permitted the enhancer to respond to the single stimulus of TPA. Therefore, both the signal requirements and the magnitude of the transcription response of the IL-2 promoter can be modulated by Oct-2

Lagrangian statistics in forced two-dimensional turbulence

We report on simulations of two-dimensional turbulence in the inverse energy cascade regime. Focusing on the statistics of Lagrangian tracer particles, scaling behavior of the probability density functions of velocity fluctuations is investigated. The results are compared to the three-dimensional case. In particular an analysis in terms of compensated cumulants reveals the transition from a strong non-Gaussian behavior with large tails to Gaussianity. The reported computation of correlation functions for the acceleration components sheds light on the underlying dynamics of the tracer particles.Comment: 8 figures, 1 tabl

Effective metadata for social book search from a user perspective

Abstract. In this extended abstract we describe our participation in the INEX 2014 Interactive Social Book Search Track. In previous work, we have looked at the impact of professional and user-generated metadata in the context of book search, and compared these different categories of metadata in terms of retrieval effectiveness. Here, we take a different approach and study the use of professional and user-generated metadata of books in an interactive setting, and the effectivity of this metadata from a user perspective. We compare the perceived usefulness of general descriptions, publication metadata, user reviews and tags in focused and open-ended search tasks, based on data gathered in the INEX Interactive Social Book Search Track. Furthermore, we take a tentative look at the actual use of different types of metadata over time in the aggregated search tasks. Our preliminary findings in the surveyed tasks indicate that user reviews are generally perceived to be more useful than other types of metadata, and they are frequently mentioned in users ’ rationales for selecting books. Furthermore, we observe a varying usage frequency of traditional and user-generated metadata across time in the aggregated search tasks, pro-viding initial indications that these types of metadata might be useful at different stages of a search task.