In multihop packet radio networks with randomly distributed terminals, the optimal transmission radii to maximize the expected progress of packets in desired directions are determined with a variety of transmission protocols and network configurations. It is shown that the FM capture phenomenon with slotted ALOHA greatly improves the expected progress over the system without capture due to the more limited area of possibly interfering terminals around the receiver. The (mini)slotted nonpersistent carrier-sense-multiple-access (CSMA) only slightly outperforms ALOHA, unlike the single-hop case (where a large improvement is available), because of a large area of "hidden" terminals and the long vulnerable period generated by them. As an example of an inhomogeneous terminal distribution, the effect of a gap in an otherwise randomly distributed terminal population on the expected progress of packets crossing the gap is considered. In this case, the disadvantage of using a large transmission radius is demonstrated.

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Plasmacytoid dendritic cells (pDCs) are characterized as type I interferon-producing cells that engage endosomal toll-like receptors (TLRs) and exclusively express sialic acid binding Ig-like lectin (Siglec)-H. However, their role in vivo remains unclear. Here we report a critical role for pDCs in the regulation of inflammation and T cell immunity in vivo by using gene-targeted mice with a deficiency of Siglec-H and conditional ablation of pDCs. pDCs were required for inflammation triggered by a TLR ligand as well as by bacterial and viral infections. pDCs controlled homeostasis of effector and regulatory CD4(+) T cells. Upon antigenic stimulation and microbial infection, pDCs suppressed the induction of CD4(+) T cell responses and participated in the initiation of CD8(+) T cell responses. Furthermore, Siglec-H appeared to modulate the function of pDCs in vivo. Thus, our findings highlight previously unidentified roles of pDCs and the regulation of their function for the control of innate and adaptive immunity.

A polling model is a system of multiple queues accessed by a single server in cyclic order. Polling models provide performance evaluation criteria for a variety of demand-based, multiple-access schemes in computer and communication systems. This paper presents an overview of the state of the art of polling model analysis, as well as an extensive list of references. In particular, single-buffer systems and infinite-buffer systems with exhaustive, gated, and limited service disciplines are treated. There is also some discussion of systems with a noncyclic order of service and systems with priority. Applications to computer networks are illustrated, and future research topics are suggested.

Unlike classical covalent polymers, one-dimensionally (1D) elongated supramolecular polymers (SPs) can be encoded with high degrees of internal order by the cooperative aggregation of molecular subunits, which endows these SPs with extraordinary properties and functions. However, this internal order has not yet been exploited to generate and dynamically control well-defined higher-order (secondary) conformations of the SP backbone, which may induce functionality that is comparable to protein folding/unfolding. Herein, we report light-induced conformational changes of SPs based on the 1D exotic stacking of hydrogen-bonded azobenzene hexamers. The stacking causes a unique internal order that leads to spontaneous curvature, which allows accessing conformations that range from randomly folded to helically folded coils. The reversible photoisomerization of the azobenzene moiety destroys or recovers the curvature of the main chain, which demonstrates external control over the SP conformation that may ultimately lead to biological functions.