On the relevance of subcritical hydrodynamic turbulence to accretion disk transport

Hydrodynamic unstratified keplerian flows are known to be linearly stable at all Reynolds numbers, but may nevertheless become turbulent through nonlinear mechanisms. However, in the last ten years, conflicting points of view have appeared on this issue. We have revisited the problem through numerical simulations in the shearing sheet limit. It turns out that the effect of the Coriolis force in stabilizing the flow depends on whether the flow is cyclonic (cooperating shear and rotation vorticities) or anticyclonic (competing shear and rotation vorticities); keplerian flows are anticyclonic. We have obtained the following results: i/ The Coriolis force does not quench turbulence in subcritical flows; ii/ The resolution demand, when moving away from the marginal stability boundary, is much more severe for anticyclonic flows than for cyclonic ones. Presently available computer resources do not allow numerical codes to reach the keplerian regime. iii/ The efficiency of turbulent transport is directly correlated to the Reynolds number of transition to turbulence $Rg$, in such a way that the Shakura-Sunyaev parameter $\alpha\sim 1/Rg$. iv/ Even the most optimistic extrapolations of our numerical data show that subcritical turbulent transport would be too inefficient in keplerian flows by several orders of magnitude for astrophysical purposes. v/ Our results suggest that the data obtained for keplerian-like flows in a Taylor-Couette settings are largely affected by secondary flows, such as Ekman circulation.Comment: 21 pages, 17 figures, accepted in Astronomy and Astrophysic

Combined effects of prevention and quarantine on a breakout in SIR model

Recent breakouts of several epidemics, such as flu pandemics, are serious threats to human health. The measures of protection against these epidemics are urgent issues in epidemiological studies. Prevention and quarantine are two major approaches against disease spreads. We here investigate the combined effects of these two measures of protection using the SIR model. We use site percolation for prevention and bond percolation for quarantine applying on a lattice model. We find a strong synergistic effect of prevention and quarantine under local interactions. A slight increase in protection measures is extremely effective in the initial disease spreads. Combination of the two measures is more effective than a single protection measure. Our results suggest that the protection policy against epidemics should account for both prevention and quarantine measures simultaneously

Carbon cycling and budget in a forested basin of southwestern Hokkaido, northern Japan

Quantification of annual carbon sequestration is very important in order to assess the function of forest ecosystems in combatting global climate change and the ecosystem responses to those changes. Annual cycling and budget of carbon in a forested basin was investigated to quantify the carbon sequestration of a cool-temperate deciduous forest ecosystem in the Horonai stream basin, Tomakomai Experimental Forest, northern Japan. Net ecosystem exchange, soil respiration, biomass increment, litterfall, soil-solution chemistry, and stream export were observed in the basin from 1999–2001 as a part of IGBP-TEMA project. We found that 258 g C m–2 year–1 was sequestered annually as net ecosystem exchange (NEE) in the forested basin. Discharge of carbon to the stream was 4 g C m–2 year–1 (about 2% of NEE) and consisted mainly of dissolved inorganic carbon (DIC). About 43% of net ecosystem productivity (NEP) was retained in the vegetation, while about 57% of NEP was sequestered in soil, suggesting that the movement of sequestered carbon from aboveground to belowground vegetation was an important process for net carbon accumulation in soil. The derived organic carbon from aboveground vegetation that moved to the soil mainly accumulated in the solid phase of the soil, with the result that the export of dissolved organic carbon to the stream was smaller than that of dissolved inorganic carbon. Our results indicated that the aboveground and belowground interaction of carbon fluxes was an important process for determining the rate and retention time of the carbon sequestration in a cool-temperate deciduous forest ecosystem in the southwestern part of Hokkaido, northern Japan

Distinct stem cells subpopulations isolated from human adipose tissue exhibit different chondrogenic and osteogenic differentiation potential

Recently adipose tissue has become a research topic also for the searching for an alternative stem cells source to use in cell based therapies such as tissue engineer. In fact Adipose Stem Cells (ASCs) exhibit an important differentiation potential for several cell lineages such as chondrogenic, osteogenic, myogenic, adipogenic and endothelial cells. ASCs populations isolated using standard methodologies (i.e., based on their adherence ability) are very heterogeneous but very few studies have analysed this aspect. Consequently, several questions are still pending, as for example, on what regard the existence/ or not of distinct ASCs subpopulations. The present study is originally aimed at isolating selected ASCs subpopulations, and to analyse their behaviour towards the heterogeneous population regarding the expression of stem cell markers and also regarding their osteogenic and chondrogenic differentiation potential. Human Adipose derived Stem Cells (hASCs) subpopulations were isolated using immunomagnetic beads coated with several different antibodies (CD29, CD44, CD49d, CD73, CD90, CD 105, Stro-1 and p75) and were characterized by Real Time RT-PCR in order to assess the expression of mesenchymal stem cells markers (CD44, CD73, Stro-1, CD105 and CD90) as well as known markers of the chondrogenic (Sox 9, Collagen II) and osteogenic lineage (Osteopontin, Osteocalcin). The obtained results underline the complexity of the ASCs population demonstrating that it is composed of several subpopulations, which express different levels of ASCs markers and exhibit distinctive differentiation potentials. Furthermore, the results obtained clearly evidence of the advantages of using selected populations in cell-based therapies, such as bone and cartilage regenerative medicine approaches.EU funded Marie Curie Actions Alea Jacta Est for a PhD fellowship. This work was carried out under the scope of the European NoE EXPERTISSUES (NMP3-CT-2004-500283)

α2,3-Sialyltransferase ST3Gal III Modulates Pancreatic Cancer Cell Motility and Adhesion In Vitro and Enhances Its Metastatic Potential In Vivo

Background: Cell surface sialylation is emerging as an important feature of cancer cell metastasis. Sialyltransferase expression has been reported to be altered in tumours and may account for the formation of sialylated tumour antigens. We have focused on the influence of alpha-2,3-sialyltransferase ST3Gal III in key steps of the pancreatic tumorigenic process. Methodology/Principal Findings: ST3Gal III overexpressing pancreatic adenocarcinoma cell lines Capan-1 and MDAPanc-28 were generated. They showed an increase of the tumour associated antigen sialyl-Lewis x. The transfectants ’ E-selectin binding capacity was proportional to cell surface sialyl-Lewis x levels. Cellular migration positively correlated with ST3Gal III and sialyl-Lewis x levels. Moreover, intrasplenic injection of the ST3Gal III transfected cells into athymic nude mice showed a decrease in survival and higher metastasis formation when compared to the mock cells. Conclusion: In summary, the overexpression of ST3Gal III in these pancreatic adenocarcinoma cell lines underlines the rol

Osteoinduction of Human Mesenchymal Stem Cells by Bioactive Composite Scaffolds without Supplemental Osteogenic Growth Factors

The development of a new family of implantable bioinspired materials is a focal point of bone tissue engineering. Implant surfaces that better mimic the natural bone extracellular matrix, a naturally nano-composite tissue, can stimulate stem cell differentiation towards osteogenic lineages in the absence of specific chemical treatments. Herein we describe a bioactive composite nanofibrous scaffold, composed of poly-caprolactone (PCL) and nano-sized hydroxyapatite (HA) or beta-tricalcium phosphate (TCP), which was able to support the growth of human bone marrow mesenchymal stem cells (hMSCs) and guide their osteogenic differentiation at the same time. Morphological and physical/chemical investigations were carried out by scanning, transmission electron microscopy, Fourier-transform infrared (FTIR) spectroscopy, mechanical and wettability analysis. Upon culturing hMSCs on composite nanofibers, we found that the incorporation of either HA or TCP into the PCL nanofibers did not affect cell viability, meanwhile the presence of the mineral phase increases the activity of alkaline phosphatase (ALP), an early marker of bone formation, and mRNA expression levels of osteoblast-related genes, such as the Runt-related transcription factor 2 (Runx-2) and bone sialoprotein (BSP), in total absence of osteogenic supplements. These results suggest that both the nanofibrous structure and the chemical composition of the scaffolds play a role in regulating the osteogenic differentiation of hMSCs

Manipulating the Hype: contemporary art's response to media cliches

Manipulating the Hype addresses art’s reaction to the barrage of signs produced by the media. The paper researches contemporary art’s response to clichéd media stereotypes and elucidates artists’ multifaceted perspective on overtly obvious yet widely embraced paradigms marketed by the media. Contemporary art’s strategic reconfiguration of media stereotypes is a valuable introspection upon the superficiality and impracticability of advertising and entertainment industry constructs. By reconsidering the mediated image, art has the ability to inspire reevaluation of cultural values. The thesis additionally attempts to ascertain the reinterpretation of media stereotypes as a common thread linking principal art movements and historically significant artworks from around the world since 1960. How does contemporary art respond to the extensive cultural influence of the media? Is a reaction to mass media a thematic commonality linking contemporary artists in the age of globalization? Manipulating the Hype is a dual outcome investigation comprised of written thesis and studio practice. The written thesis combines experience from a lengthy professional practice with historical and theoretical research. The visual thesis consists of twelve photographic works taken at on the Big Island of Hawaii. The images juxtapose artificial icons of power from popular culture with the natural force of the active lava flow. The process of research discloses how the advertising and entertainment industries capitalize upon innate human desires through the manipulative proliferation of archetypal imagery. Furthermore, the thesis establishes the widespread retort to media clichés as a palpable commonality in studio practices worldwide. The findings in the research make evident that although contemporary art does not have sufficient influence to reform the media, it can heighten public awareness of media tactics