Although it is widely supposed that chemokines play a role in the thymus, most existing evidence is circumstantial. In this issue, two groups provide direct evidence that the chemokine receptor CCR7 is required for normal thymocyte migration (Ueno, T., F. Saito, D. Gray, S. Kuse, K. Hieshima, H. Nakano, T. Kakiuchi, M. Lipp, R. Boyd, and Y. Takahama. 2004. J. Exp. Med. 200:493-505; Misslitz, A....

Let $k$ be field of characteristic $p$, andlet $G$ be any finite group with splitting field $k$. Assume that $B$ is a $p$-block of $G$.In this paper, we introduce the notion of radical $B$-chain $C_{B}$, and we show that the $p$-local rank of $B$ is equals the length of $C_{B}$. Moreover, we prove that the vertex of a simple $kG$-module $S$ is radical if and only if it has the same vertex of th...

We consider the problem of testing whether a Boolean function has Fourier degree ≤ k or it is ǫ-far from any Boolean function with Fourier degree ≤ k, we improve the known lower bound of Ω(k) [4, 6], to Ω(k/ √ ǫ). The lower bound uses the recently discovered connections between property testing and communication complexity by Blais et. al. [4]

We study the problem of estimating the best k term Fourier representation for a given frequency-sparse signal (i.e., vector) A of length N k. More explicitly, we investigate how to deterministically identify k of the largest magnitude frequencies of Â, and estimate their coefficients, in polynomial(k, log N) time. Randomized sublinear time algorithms which have a small (controllable) probabilit...

This paper presents a theory of dynamic slicing, which reveals that the relationship between static and dynamic slicing is more subtle than previously thought. The definitions of dynamic slicing are formulated in terms of the projection theory of slicing. This shows that existing forms of dynamic slicing contain three orthogonal dimensions in their slicing criteria and allows for a lattice-theo...

We outline a model of dimensional reasoning on time and space scales which integrates quantitative and qualitative knowledge about distances. At the core of this model lie constraints on interval boundaries, partial ordering and subsumption relations on interval relations and interval boundary constraints, as well as the transformation of interval relations to interval boundary constraints and ...

Finite model reasoning in expressive DLs such as ALCQI and SHIQ requires non-trivial algorithmic approaches that are substantially differerent from algorithms used for reasoning about unrestricted models. In contrast, finite model reasoning in the inexpressive fragment DL-LiteF of ALCQI and SHIQ is algorithmically rather simple: using a TBox completion procedure that reverses certain terminolog...

To align representations of law, of implementations of law and of concrete behaviours, we designed a common ground representational model for the three domains, based on the notion of position, building upon Petri nets. This paper reports on work to define subsumption between positional models.