A Methodology to Measure the Hierarchical Degree of Formal Organizations

Hierarchy is a fundamental phenomenon in management and organization science, a phenomenon which has marked the evolution of human societies over centuries. Among the many studies on this issue, the ones that adopt a formal approach of investigation are mainly based on social network analysis. Following this line, in this work we focus on organization distribution of formal direct authority in stylized, pure hierarchical archetypes. Past research, analyzing the share of asymmetric links in out-tree topologies, was not able to distinguish among different types of out-trees. Indeed since the out-trees can differ under substantial structural features, in order to measure the degree of hierarchy it is necessary to employ indicators of power concentration and distribution. Results show that the purest archetype of hierarchy is the star form, and not the typical org chart. Further, ceteris paribus, an organization with more hierarchical levels is less and not more hierarchical than an organization with fewer levels. Moreover, power tend to concentrate in lower levels, and especially into the penultimate one.

miR-155 and its star-form partner miR-155* cooperatively regulate type I interferon production by human plasmacytoid dendritic cells

The recent discovery of microRNAs (miRNAs) has revealed a new layer of gene expression regulation, affecting the immune system. Here, we identify their roles in regulating human plasmacytoid dendritic cell (PDC) activation. miRNA profiling showed the significantly differential expression of 19 miRNAs in PDCs after Toll-like receptor 7 (TLR7) stimulation, among which miR-155* and miR-155 were the most highly induced. Although they were processed from a single precursor and were both induced by TLR7 through the c-Jun N-terminal kinase pathway, miR-155* and miR-155 had opposite effects on the regulation of type I interferon production by PDC. Further study indicated that miR-155* augmented interferon-α/β expression by suppressing IRAKM, whereas miR-155 inhibited their expression by targeting TAB2. Kinetic analysis of miR-155* and miR-155 induction revealed that miR-155* was mainly induced in the early stage of stimulation, and that miR-155 was mainly induced in the later stage, suggesting their cooperative involvement in PDC activation. Finally, we demonstrated that miR-155* and miR-155 were inversely regulated by autocrine/paracrine type I interferon and TLR7-activated KHSRP at the posttranscriptional level, which led to their different dynamic induction by TLR7. Thus, our study identified and validated novel miRNA-protein networks involved in regulating PDC activation.

From Infall to Rotation around Young Stars: The Origin of Protoplanetary Disks

The origin of disks surrounding young stars has direct implications for our understanding of the formation of planetary systems. In the interstellar clouds from which star form, angular momentum is regulated by magnetic fields, preventing the spin up of contracting cores. When ∼ 0.03 pc-sized dense cores decouple from the magnetic field and collapse dynamically, ∼ 10−3 km s−1 pc of specific angular momentum is locked into the system. A viscous accretion disk is one of two possible mechanisms available for the necessary redistribution of angular momentum; the other one is the formation of a multiple stellar system. Recent observational results involving high-angular resolution observations are reviewed: the presence of disks deep inside collapsing envelopes; an accretion shock surrounding a disk; the velocity field in collapsing and slowly rotating envelopes; a possible transitional object, characterized as a large, contracting disk; and the velocity field in disks around T Tauri stars. Observational facilities becoming available over the next several years promise to offer significant progress in the study of the origin of protoplanetary disks.

Ultrastructural studies of an aquatic bacterium, seliberia stellata

Seliberia stellata is a bacterium first isolated from tundra soil and described as a spirally twisted rod having one subpolar flagellum and reproducing by fission or budding. The cells stick at their poles forming a rosette or star form. Although this procaryotic organism has been noted in aquatic environments such as fresh water ponds and laboratory distilled water, strains from these habitats have apparently not been obtained in pure culture. We have isolated the bacteria from two fresh water sources and maintained them as pure cultures in dilute peptone-yeast extract broth or 1% agar media.Isolation of two strains of these organisms was achieved by enriching water samples with 0. 005% peptone. Enrichment culture surfaces were evaluated for the presence of bacteria by placing carbon-stabilized formvar grids onto the unbroken surface film followed by immediate removal and staining with 0. 25 or 0. 5% potassium phosphotungstate for TEM. The occurrence of Seliberia-like cells in these enrichments was rare (approximately 1/1000).