Low-dimensional dynamics embedded in a plane Poiseuille flow turbulence : Traveling-wave solution is a saddle point ?

The instability of a streak and its nonlinear evolution are investigated by direct numerical simulation (DNS) for plane Poiseuille flow at Re=3000. It is suggested that there exists a traveling-wave solution (TWS). The TWS is localized around one of the two walls and notably resemble to the coherent structures observed in experiments and DNS so far. The phase space structure around this TWS is similar to a saddle point. Since the stable manifold of this TWS is extended close to the quasi two dimensional (Q2D) energy axis, the approaching process toward the TWS along the stable manifold is approximately described as the instability of the streak (Q2D flow) and the succeeding nonlinear evolution. Bursting corresponds to the escape from the TWS along the unstable manifold. These manifolds constitute part of basin boundary of the turbulent state.Comment: 5 pages, 6 figure

Definitive Management of Failure After Pyeloplasty

Introduction: Failure after pyeloplasty is difficult to manage. We report our experience managing pyeloplasty failures. Methods: We retrospectively reviewed the case log of a single surgeon, from August 1996 to August 2014, to identify all patients undergoing a surgical procedure after failed pyeloplasty. We excluded patients without follow-up exceeding 1 year from initial postpyeloplasty procedure. Failure was defined as a need for additional definitive intervention. Results: Of 247 laparoscopic pyeloplasties, 68 endopyelotomies and 305 simple laparoscopic nephrectomies reviewed, 41 were performed after previous pyeloplasty and had sufficient follow-up. Laparoscopic nephrectomy was performed in nine patients. All three secondary laparoscopic pyeloplasties were successful. Of 29 secondary endopyelotomies, 10 (34%) were successful. Of the 19 failures after secondary endopyelotomy, 12 patients had tertiary pyeloplasty (5 laparoscopic and 7 open surgical), 5 (26%) underwent tertiary endopyelotomy, and 2 (11%) required nephrectomy. Our overall endopyelotomy success rate was 38% (13/34) vs 100% (11/11) for secondary or tertiary pyeloplasty (4 patients lost to follow-up). Median time to failure was 5 months for endopyelotomy. Median follow-up for patients free from intervention was 40.2 months. Conclusions: Secondary pyeloplasty (including both laparoscopic and open surgical approach) is more than twice as successful as endopyelotomy after failed pyeloplasty. Secondary pyeloplasty is an excellent alternative to endopyelotomy in select patients with failure after initial pyeloplasty.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/140085/1/end.2015.0837.pd

Resolving the gap and AU-scale asymmetries in the pre-transitional disk of V1247 Orionis

Pre-transitional disks are protoplanetary disks with a gapped disk structure, potentially indicating the presence of young planets in these systems. In order to explore the structure of these objects and their gap-opening mechanism, we observed the pre-transitional disk V1247 Orionis using the Very Large Telescope Interferometer, the Keck Interferometer, Keck-II, Gemini South, and IRTF. This allows us spatially resolve the AU-scale disk structure from near- to mid-infrared wavelengths (1.5 to 13 {\mu}m), tracing material at different temperatures and over a wide range of stellocentric radii. Our observations reveal a narrow, optically-thick inner-disk component (located at 0.18 AU from the star) that is separated from the optically thick outer disk (radii >46 AU), providing unambiguous evidence for the existence of a gap in this pre-transitional disk. Surprisingly, we find that the gap region is filled with significant amounts of optically thin material with a carbon-dominated dust mineralogy. The presence of this optically thin gap material cannot be deduced solely from the spectral energy distribution, yet it is the dominant contributor at mid-infrared wavelengths. Furthermore, using Keck/NIRC2 aperture masking observations in the H, K', and L' band, we detect asymmetries in the brightness distribution on scales of about 15-40 AU, i.e. within the gap region. The detected asymmetries are highly significant, yet their amplitude and direction changes with wavelength, which is not consistent with a companion interpretation but indicates an inhomogeneous distribution of the gap material. We interpret this as strong evidence for the presence of complex density structures, possibly reflecting the dynamical interaction of the disk material with sub-stellar mass bodies that are responsible for the gap clearing.Comment: 16 pages, 17 Figures, accepted by Astrophysical Journa

Panchromatic Imaging of a Transitional Disk: The Disk of GM Aur in Optical and FUV Scattered Light

We have imaged GM Aur with HST, detected its disk in scattered light at 1400A and 1650A, and compared these with observations at 3300A, 5550A, 1.1 microns, and 1.6 microns. The scattered light increases at shorter wavelengths. The radial surface brightness profile at 3300A shows no evidence of the 24AU radius cavity that has been previously observed in sub-mm observations. Comparison with dust grain opacity models indicates the surface of the entire disk is populated with sub-micron grains. We have compiled an SED from 0.1 microns to 1 mm, and used it to constrain a model of the star+disk system that includes the sub-mm cavity using the Monte Carlo Radiative Transfer code by Barbara Whitney. The best-fit model image indicates that the cavity should be detectable in the F330W bandpass if the cavity has been cleared of both large and small dust grains, but we do not detect it. The lack of an observed cavity can be explained by the presence of sub-microns grains interior to the sub-mm cavity wall. We suggest one explanation for this which could be due to a planet of mass <9 Jupiter masses interior to 24 AU. A unique cylindrical structure is detected in the FUV data from the Advanced Camera for Surveys/Solar Blind Channel. It is aligned along the system semi-minor axis, but does not resemble an accretion-driven jet. The structure is limb-brightened and extends 190 +/- 35 AU above the disk midplane. The inner radius of the limb-brightening is 40 +/- 10 AU, just beyond the sub-millimeter cavity wall.Comment: 40 pages, 11 figures, 4 tables, accepted to Ap

Prospectus, February 28, 2008

https://spark.parkland.edu/prospectus_2008/1004/thumbnail.jp

Planting Food or Fuel: Developing an Interdisciplinary Approach to Understanding the Role of Culture in Farmers’ Decisions to Grow Second-Generation Biofuel Feedstock Crops

Recent interest in biofuels as an alternative energy source has spurred considerable changes in agricultural practice worldwide. These changes will be more pronounced as second-generation biofuels, such as switch grass, gain prominence; this article examines the cultural factors associated with the decisions U.S. farmers face in targeting crops for fuel production instead of food. Through an interdisciplinary assessment of the dynamics of farmers' behavior, developed herein is a theoretical framework to analyze how farmers grapple with shifting expectations of their function.National Science Foundation EPS-0903806, KU-Transportation Research Institut

Prospectus, April 10, 2008

https://spark.parkland.edu/prospectus_2008/1009/thumbnail.jp

Prospectus, March 13, 2008

https://spark.parkland.edu/prospectus_2008/1006/thumbnail.jp

Prospectus, April 17, 2008

https://spark.parkland.edu/prospectus_2008/1010/thumbnail.jp