RNA functions broadly as informational molecule, genome, enzyme and machinery for RNA processing. While these functions reflect ancient activities, they also remain vital components of contemporary biochemical pathways. In eukaryotic cells RNA processing impacts the biogenesis of RNA molecules of essentially every shape and function. The collection of articles in this volume describes the current state of understanding of the broad array of RNA processing events in animal and plant cells, key unanswered questions, and cutting edge approaches available to address these questions. Some questions discussed in this volume include, how viruses subvert the RNA processing machinery of the host cell, how the coordination of co-transcriptional RNA processing is regulated at the level of chromatin, the status of RNA processing in plant organelles, and how micro RNA machinery is biosynthesized and regulated.

Electron transport in III-V semiconductors, especially the Ga/As/AlGaAs material systems, is studied in various nonequilibrium situations. Throughout the study, a Monte Carlo simulation method is used for the analysis of transport properties in the semiclassical Boltzmann transport picture. The present work essentially consists of two aspects. The first topic is hot electron transport in GaAs, focusing on the electron impact ionization effects. The dependence of impact ionization rates on the details of the band structure is investigated by using two (local and nonlocal) pseudopotential methods. The spatial evolution of the ionization rate and the average electron energy are studied in nonuniform fields characteristic of p+-n junctions. The effects of field fluctuations due to the random distribution of dopants are studied as well. The possibility of new GaAs electron-emitting diodes is explored numerically and compared with the corresponding Si devices. The second aspect deals with the effects of conduction band discontinuities on the electron transport. In particular, one-dimensional heterostructures are modeled to study the nonlinear transport across heterointerfaces. (RH).

RNA Processing Activities of the Arabidopsis Argonaute Protein Family.

Abstract: Monocytes are circulating mononuclear phagocytes, poised to extravasate to sites of inflammation and differentiate into monocyte-derived macrophages and dendritic cells. Tumor necrosis factor (TNF) and its receptors are up-regulated during monopoiesis and expressed by circulating monocytes, as well as effector monocytes infiltrating certain sites of inflammation, such as the spinal cord, during experimental autoimmune encephalomyelitis (EAE). In this study, using competitive in vitro and in vivo assays, we show that monocytes deficient for TNF or TNF receptors are outcompeted by their wild-type counterpart. Moreover, monocyte-autonomous TNF is critical for the function of these cells, as TNF ablation in monocytes/macrophages, but not in microglia, delayed the onset of EAE in challenged animals and was associated with reduced acute spinal cord infiltration of Ly6Chi effector monocytes. Collectively, our data reveal a previously unappreciated critical cell-autonomous role of TNF on monocytes for their survival, maintenance, and function