Design Patterns for Fusion-Based Object Retrieval

We address the task of ranking objects (such as people, blogs, or verticals) that, unlike documents, do not have direct term-based representations. To be able to match them against keyword queries, evidence needs to be amassed from documents that are associated with the given object. We present two design patterns, i.e., general reusable retrieval strategies, which are able to encompass most existing approaches from the past. One strategy combines evidence on the term level (early fusion), while the other does it on the document level (late fusion). We demonstrate the generality of these patterns by applying them to three different object retrieval tasks: expert finding, blog distillation, and vertical ranking.Comment: Proceedings of the 39th European conference on Advances in Information Retrieval (ECIR '17), 201

Looking at things differently: Exploring perspective recall for informal text retrieval

When retrieving informal text such as blogs, comments, contributions to discussion forums, users often want to uncover different perspectives on a given issue. To help uncover perspectives, we examine the use of query expansion against multiple external corpora. We consider two informal text retrieval tasks: blog post finding and blog finding. We operationalize the idea of uncovering multiple perspectives by query expansion against multiple corpora from different genres. We use two approaches to incorporate these perspectives: as a rank-based combination of runs and a mixture of query models. The use of external sources does indeed generate different views on a topic as becomes clear from the unique relevant results identified by the expanded runs compared to the baseline run. Even after combining the expanded run with the original run, unique relevant documents are found by both of the perspectives. As to the combination methods, the mixture of query models outperforms the rank combination, and leads to significant improvements in MAP score over the baseline

News Comments: Exploring, Modeling, and Online Prediction

Abstract. Online news agents provide commenting facilities for their readers to express their opinions or sentiments with regards to news stories. The number of user supplied comments on a news article may be indicative of its importance, interestingness, or impact. We explore the news comments space, and compare the log-normal and the negative binomial distributions for modeling comments from various news agents. These estimated models can be used to normalize raw comment counts and enable comparison across different news sites. We also examine the feasibility of online prediction of the number of comments, based on the volume observed shortly after publication. We report on solid performance for predicting news comment volume in the long run, after short observation. This prediction can be useful for identifying news stories with the potential to “take off, ” and can be used to support front page optimization for news sites.

From blogs to news: identifying hot topics in the blogosphere

Abstract: We describe the participation of the University of Amsterdam’s ILPS group in the blog track at TREC 2009. We focus on the top sto-ries identification task, and take an approach that does not require the headlines of top stories to be known beforehand. We explore the feasibility of a so-called blogs to news approach: given a date and a set of blog posts, identify the main topics for that date. This approach is more general than just find-ing top stories, but it can still be applied to the task of headline ranking. Results show that this general approach, applied to the task at hand, is among the top performing approaches in this year’s TREC.

Molecular Regulation of Early T-Cell Development in the Thymus

The human body is under constant siege of pathogens - bacteria, viruses, fungi and parasites. We can only survive because these attackers are continuously fought off by our immune system. Important tasks within the immune system of vertebrates are performed by T lymphocytes, the executors of speci.c, cellular immunity. The speci.city of T lymphocytes lies in their T-cell receptor (TCR), through which they sense the presence of antigens in their environment. Each T cell expresses a TCR with a unique antigen-recognition site, so all T cells together can respond to an enormous variety of antigens. The highly diverse T-cell repertoire is generated by random recombination of discrete TCR gene segments. Via the TCR, T cells recognize peptide antigens that are displayed by antigen presenting cells (APCs), in the context of major histocompatibility complex (MHC) class I or class II molecules. Mature T cells carry out their function in cellular immunity as either CD8+ cytotoxic T cells or as CD4+ helper T cells. The humoral part of the speci.c immune system is supplied by B lymphocytes, which can secrete their antigen receptors in the form of antibodies. T cells develop from multipotent precursors via a highly ordered, but complex differentiation pathway. A number of critical events occur during this T-cell development process. Cells proliferate, adopt a T-cell fate, and produce a TCR molecule via a strictly ordered process of gene rearrangements. Stringent selection processes make sure that the produced TCR molecule is self-MHC restricted but not reactive to self-antigens. Finally, the selected T cells are allowed to mature into functional effector T cells. To become highly differentiated and thoroughly ‘educated’ cells, T cells need a specialized microenvironment for their development. The organ which has evolved to ful.ll this task and which also gave T cells their name, is the Thymus. The hematopoietic cells that undergo T-cell development in the thymus are called thymocytes. The importance of the thymus as essential microenvironment for T-cell development is illustrated by children af.icted by the DiGeorge syndrome, who sometimes completely lack a thymus. These children have severely reduced T cell numbers and suffer from recurrent life-threatening infections. DiGeorge syndrome also illustrates the fact that T cells are the only hematopoietic cell type that absolutely require the thymus for their development. Although human T-cell development is the main theme of this thesis, most of the published knowledge about T-cell differentiation has been acquired by studies in the mouse