Predictive protocol of flocks with small-world connection pattern

By introducing a predictive mechanism with small-world connections, we propose a new motion protocol for self-driven flocks. The small-world connections are implemented by randomly adding long-range interactions from the leader to a few distant agents, namely pseudo-leaders. The leader can directly affect the pseudo-leaders, thereby influencing all the other agents through them efficiently. Moreover, these pseudo-leaders are able to predict the leader's motion several steps ahead and use this information in decision making towards coherent flocking with more stable formation. It is shown that drastic improvement can be achieved in terms of both the consensus performance and the communication cost. From the industrial engineering point of view, the current protocol allows for a significant improvement in the cohesion and rigidity of the formation at a fairly low cost of adding a few long-range links embedded with predictive capabilities. Significantly, this work uncovers an important feature of flocks that predictive capability and long-range links can compensate for the insufficiency of each other. These conclusions are valid for both the attractive/repulsive swarm model and the Vicsek model.Comment: 10 pages, 12 figure

Community Seismic Network

The article describes the design of the Community Seismic Network, which is a dense open seismic network based on low cost sensors. The inputs are from sensors hosted by volunteers from the community by direct connection to their personal computers, or through sensors built into mobile devices. The server is cloud-based for robustness and to dynamically handle the load of impulsive earthquake events. The main product of the network is a map of peak acceleration, delivered within seconds of the ground shaking. The lateral variations in the level of shaking will be valuable to first responders, and the waveform information from a dense network will allow detailed mapping of the rupture process. Sensors in buildings may be useful for monitoring the state-of-health of the structure after major shaking

Inner Molecular Rings in Barred Galaxies: BIMA SONG CO Observations

Although inner star-forming rings are common in optical images of barred spiral galaxies, observational evidence for the accompanying molecular gas has been scarce. In this paper we present images of molecular inner rings, traced using the CO (1-0) emission line, from the Berkeley-Illinois-Maryland-Association Survey of Nearby Galaxies (BIMA SONG). We detect inner ring CO emission from all five SONG barred galaxies classified as inner ring (type (r)). We also examine the seven SONG barred galaxies classified as inner spiral (type (s)); in one of these, NGC 3627, we find morphological and kinematic evidence for a molecular inner ring. Inner ring galaxies have been classified as such based on optical images, which emphasize recent star formation. We consider the possibility that there may exist inner rings in which star formation efficiency is not enhanced. However, we find that in NGC 3627 the inner ring star formation efficiency is enhanced relative to most other regions in that galaxy. We note that the SONG (r) galaxies have a paucity of CO and H alpha emission interior to the inner ring (except near the nucleus), while NGC 3627 has relatively bright bar CO and H alpha emission; we suggest that galaxies with inner rings such as NGC 3627 may be misclassified if there are significant amounts of gas and star formation in the bar.Comment: To be published in the Astrophysical Journal, July 2002 A version of the paper with full resolution figures is available at: http://www.astro.umd.edu/~mregan/ms.ps.g

The Influence of Juncus-rhizosphere Dissolved Organic Matter on Coastal Plankton Communities

Many aquatic plants produce copious amounts of dissolved organic matter (DOM) which enters surrounding waters and potentially stimulates planktonic activity. In the northern Gulf of Mexico, Juncus roemarianus (i.e. black needlerush) is a dominant marsh grass species residing in coastal zones and barrier islands. The below-ground biomass i.e. rhizosphere, can be consistently submerged, serving as a potential source of DOM to the surrounding waters. The lability and possible stimulatory effect of J. roemarianus DOM was examined for three plankton communities collected within the discharge region of Mobile Bay and adjacent waters of Gulf Shores, Alabama (less affected by Mobile Bay). DOM within the pore water surrounding the J. roemarianus was extracted, concentrated, and added to the field communities along with positive (i.e. addition of labile organic matter) and negative (i.e. no additions) controls. In the Mobile Bay experiment, the DOM addition stimulated increased autotrophic biomass and heterotrophic activity well above that observed in the negative controls. However, experiments utilizing Gulf Shores water showed little to no stimulation. Our results suggest that J. roemarianus DOM addition may stimulate planktonic activity; however, the degree of enhancement is likely controlled by the community composition and water properties (e.g. nutrient availability)

Diatom control of the autotrophic community and particle export in the eastern Bering Sea during the recent cold years (2008–2010)

The southeastern Bering Sea has exhibited shifts in climate since the start of the 21st century. The regional climate shifts are manifested in the duration and areal extent of seasonal sea-ice coverage. During a recent cold period (2008–2010) with extensive spring sea-ice cover over the southeastern shelf of the Bering Sea, a total of 77 water column and 24 sediment trap profiles were collected over the shelf and shelf break and analyzed for autotrophic pigment concentrations and elemental (carbon, nitrogen, phosphorus, and silicon) concentrations in suspended and exported particulate material. These results are used to establish the seasonal succession of the autotrophic community and the control that both phytoplankton and zooplankton exert on export production. In spring (April to mid-June), total chlorophyll a (TChl a) concentrations were generally low (i.e., \u3c 1 μg L–1); however, localized phytoplankton blooms near the marginal ice zone (MIZ) lead to elevated spring average TChl a concentrations (i.e., \u3e5 μg L–1). In summer (mid-June to late July), photic zone chlorophyll a concentrations were typically \u3c1 μg L–1 over the shelf and at the shelf break. Diatoms represented the greatest contribution to TChl a (regional averages of 71%–96% in spring and 25%–75% in summer) and autotrophic biomass in spring and summer. This algal class also represented 50%–99% of TChl a associated with particles sinking from the photic zone. The relatively high proportion of phaeophorbide a in sediment trap material indicates that sinking of zooplankton fecal pellets facilitate the export of particles through the water column. Further, zooplankton grazing may be an important process that returns regenerated nutrients to the water column based on the elemental composition of suspended and sinking particles. In colder than average years, the emergence of diatom blooms in the spring MIZ supports the production of abundant large zooplankton, which are a primary food source for juvenile pelagic fishes of economically important species. Therefore, processes in colder than average years may be essential for the transfer of particulate organic carbon from the surface waters and the success of the economically important pelagic fisheries

Tumor Necrosis Factor Alpha and Insulin-Like Growth Factor 1 Induced Modifications of the Gene Expression Kinetics of Differentiating Skeletal Muscle Cells

Introduction TNF-alpha levels are increased during muscle wasting and chronic muscle degeneration and regeneration processes, which are characteristic for primary muscle disorders. Pathologically increased TNF-alpha levels have a negative effect on muscle cell differentiation efficiency, while IGF1 can have a positive effect;therefore, we intended to elucidate the impact of TNF-alpha and IGF1 on gene expression during the early stages of skeletal muscle cell differentiation. Methodology/Principal Findings This study presents gene expression data of the murine skeletal muscle cells PMI28 during myogenic differentiation or differentiation with TNF-alpha or IGF1 exposure at 0 h, 4 h, 12 h, 24 h, and 72 h after induction. Our study detected significant coregulation of gene sets involved in myoblast differentiation or in the response to TNF-alpha. Gene expression data revealed a time-and treatment-dependent regulation of signaling pathways, which are prominent in myogenic differentiation. We identified enrichment of pathways, which have not been specifically linked to myoblast differentiation such as doublecortin-like kinase pathway associations as well as enrichment of specific semaphorin isoforms. Moreover to the best of our knowledge, this is the first description of a specific inverse regulation of the following genes in myoblast differentiation and response to TNF-alpha: Aknad1, Cmbl, Sepp1, Ndst4, Tecrl, Unc13c, Spats2l, Lix1, Csdc2, Cpa1, Parm1, Serpinb2, Aspn, Fibin, Slc40a1, Nrk, and Mybpc1. We identified a gene subset (Nfkbia, Nfkb2, Mmp9, Mef2c, Gpx, and Pgam2),which is robustly regulated by TNF-alpha across independent myogenic differentiation studies. Conclusions This is the largest dataset revealing the impact of TNF-alpha or IGF1 treatment on gene expression kinetics of early in vitro skeletal myoblast differentiation. We identified novel mRNAs, which have not yet been associated with skeletal muscle differentiation or response to TNF-alpha. Results of this study may facilitate the understanding of transcriptomic networks underlying inhibited muscle differentiation in inflammatory diseases

Exploring Terrestrial Planet Formation in the TW Hydrae Association

Spitzer Space Telescope infrared measurements are presented for 24 members of the TW Hydrae association (TWA). High signal-to-noise 24-micron (um) photometry is presented for all of these stars, including 20 stars that were not detected by IRAS. Among these 20 stars, only a single object, TWA 7, shows excess emission at 24um and at the level of only 40% above the star's photosphere. TWA 7 also exhibits a strong 70um excess that is a factor of 40 brighter than the stellar photosphere at this wavelength. At 70um, an excess of similar magnitude is detected for TWA 13, though no 24um excess was detected for this binary. For the 18 stars that failed to show measurable IR excesses, the sensitivity of the current 70um observations does not rule out substantial cool excesses at levels 10-40x above their stellar continua. Measurements of two T Tauri stars, TW Hya and Hen 6-300, confirm that their spectacular IR spectral energy distributions (SEDs) do not turn over even by 160um, consistent with the expectation for their active accretion disks. In contrast, the Spitzer data for the luminous planetary debris systems in the TWA, HD 98800B and HR 4796A, are consistent with single-temperature blackbody SEDs. The major new result of this study is the dramatic bimodal distribution found for the association in the form of excess emission at a wavelength of 24um, indicating negligible amounts of warm (>100 K) dust and debris around 20 of 24 stars in this group of very young stars. This bimodal distribution is especially striking given that the four stars in the association with strong IR excesses are >100x brighter at 24um than their photospheres

The Neandertal genome and ancient DNA authenticity

Recent advances in high-thoughput DNA sequencing have made genome-scale analyses of genomes of extinct organisms possible. With these new opportunities come new difficulties in assessing the authenticity of the DNA sequences retrieved. We discuss how these difficulties can be addressed, particularly with regard to analyses of the Neandertal genome. We argue that only direct assays of DNA sequence positions in which Neandertals differ from all contemporary humans can serve as a reliable means to estimate human contamination. Indirect measures, such as the extent of DNA fragmentation, nucleotide misincorporations, or comparison of derived allele frequencies in different fragment size classes, are unreliable. Fortunately, interim approaches based on mtDNA differences between Neandertals and current humans, detection of male contamination through Y chromosomal sequences, and repeated sequencing from the same fossil to detect autosomal contamination allow initial large-scale sequencing of Neandertal genomes. This will result in the discovery of fixed differences in the nuclear genome between Neandertals and current humans that can serve as future direct assays for contamination. For analyses of other fossil hominins, which may become possible in the future, we suggest a similar ‘boot-strap' approach in which interim approaches are applied until sufficient data for more definitive direct assays are acquired

Large-scale Dynamo Action Driven by Velocity Shear and Rotating Convection

By incorporating a large-scale shear flow into turbulent rotating convection, we show that a sufficiently strong shear can promote dynamo action in flows that in the absence of shear do not act as dynamos. Our results are consistent with a dynamo driven by either the shear-current effect or by the interaction between a fluctuating $\alpha$-effect and the velocity shear; they are though inconsistent with either a classical $\alpha^2$ or $\alpha \omega$ mean field dynamo.Comment: 4 pages, 4 fig