739 research outputs found

    Optimal active control for Burgers equations

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    A method for active fluid flow control based on control theory is discussed. Dynamic programming and fixed point successive approximations are used to accommodate the nonlinear control problem. The long-term goal of this project is to establish an effective method applicable to complex flows such as turbulence and jets. However, in this report, the method is applied to stochastic Burgers equation as an intermediate step towards this goal. Numerical results are compared with those obtained by gradient search methods

    Stronger Radial Attraction: A Generalization of Radial Curvature bounded from above

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    This paper introduces and investigates a generalization of the notion of a pointed Riemannian manifold having its radial curvature bounded from above by that of a model surface of revolution.Comment: 29 pages, 4 figure

    The correlation between the 500 pc scale molecular gas masses and AGN powers for massive elliptical galaxies

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    Massive molecular clouds have been discovered in massive elliptical galaxies at the center of galaxy clusters. Some of this cold gas is expected to flow in the central supermassive black holes and activate galactic nucleus (AGN) feedback. In this study, we analyze archival ALMA data of 9 massive elliptical galaxies, focusing on CO line emissions, to explore the circumnuclear gas. We show that the mass of the molecular gas within a fixed radius (500 pc) from the AGNs (M_mol ~ 10^7-10^8 M_sun) is correlated with the jet power estimated from X-ray cavities (P_cav ~ 10^42-10^45 erg/s). The mass accretion rate of the circumnuclear gas \dot{M} also has a correlation with P_cav. On the other hand, the continuum luminosities at ~1.4 GHz and ~100-300 GHz have no correlation with M_mol. These results indicate that the circumnuclear gas is sustaining the long-term AGN activities (~10^7 yr) rather than the current ones. The circumnuclear gas mass is a better indicator of the jet power than the continuum luminosity, which probably changes on a shorter time scale. We also study the origin of the continuum emission from the AGNs at ~100-300 GHz and find that it is mostly synchrotron radiation. For low-luminosity AGNs, however, dust emission appears to contaminate the continuum.Comment: Accepted for publication in PAS

    Laparoscopic total colectomy with lymph node dissection for familial adenomatous polyposis with multiple colorectal cancers

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     A 49-year-old Japanese man visited our hospital with chief complaints of difficulty with and bleeding during defecation. After a detailed examination, he was diagnosed with familial adenomatous polyposis (FAP) with multiple (five) colorectal cancers. The tumors were located in the right-sided, left-sided, and sigmoid colon, and the lower rectum. Regional lymph node involvement was observed, but no metastasis to other organs was detected. We, therefore, performed a laparoscopic total colectomy with superior mesenteric artery (SMA) and inferior mesenteric artery (IMA) lymph node dissection. We were able to perform minimally invasive and cosmetically acceptable surgery using laparoscopy instead of highly-invasive open abdominal surgery. Our search of the literature revealed no reported cases of laparoscopic total colectomy with lymph node dissection for FAP with multiple colorectal cancers, making the present case the first to be reported in the literature
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