In Takagi Phys. Rev. E 92 (2015) 023020, based on copepod observations, Takagi proposed a model to interpret the swimming behaviour of these microorganisms using sinusoidal paddling or sequential ...paddling followed by a recovery stroke in unison, and compares them invoking the concept of efficiency. Our aim is to provide an interpretation of Takagi’s results in the frame of optimal control theory and sub-Riemannian geometry. The maximum principle is used to select two types of periodic control candidates as minimizers: sinusoidal up to time reparameterization and the sequential paddling, interpreted as an abnormal stroke in sub-Riemannian geometry. Geometric analysis combined with numerical simulations are decisive tools to compute the optimal solutions, refining Takagi computations. A family of simple strokes with small amplitudes emanating from a center is characterized as an invariant of SR-geometry and allows to identify the metric used by the swimmer. The notion of efficiency is discussed in detail and related with normality properties of minimizers.
Hypertriglyceridemia is infrequently reported as a cause of suboptimal delivery of dialytic therapy in critically ill patients. We report the case of a critically ill liver transplant patient in the ...Intensive Care Unit who was found to have recurrent filter clotting during continuous renal replacement therapy (CRRT). The patient had increased serum triglycerides (TGs), which was identified approximately 2 weeks into hospitalization and initially believed to be due to prolonged propofol use. The patient's elevated TGs ultimately caused her blood to become lipemic, causing the dialytic circuit to become nonfunctional and placed the patient in imminent danger due to hyperkalemia and metabolic acidosis. Therapeutic plasma exchange was emergently used to lower TG levels, and renal replacement therapy was resumed without any other issues. The patient's persistent hypertriglyceridemia was attributed to a combination of adverse effect of medications and liver graft failure. The high TG level and abnormal liver functions improved after a repeat liver transplantation.
Single-mode waveguides for GRAVITY Perraut, K.; Jocou, L.; Berger, J. P. ...
Astronomy and astrophysics (Berlin),
06/2018, Volume:
614
Journal Article
Peer reviewed
Open access
Context.
Within the framework of the second-generation instrumentation of the Very Large Telescope Interferometer of the European Southern Observatory we have developed the four-telescope beam ...combiner in integrated optics.
Aims.
We optimized the performance of such beam combiners, for the first time in the near-infrared
K
band, for the GRAVITY instrument dedicated to the study of the close environment of the galactic centre black hole by precision narrow-angle astrometry and interferometric imaging.
Methods.
We optimized the design of the integrated optics chip and the manufacturing technology as well, to fulfil the very demanding throughput specification. We also designed an integrated optics assembly able to operate at 200 K in the GRAVITY cryostat to reduce thermal emission.
Results.
We manufactured about 50 beam combiners by silica-on-silicon etching technology. We glued the best combiners to single-mode fluoride fibre arrays that inject the VLTI light into the integrated optics beam combiners. The final integrated optics assemblies have been fully characterized in the laboratory and through on-site calibrations: their global throughput over the
K
band is higher than 55% and the instrumental contrast reaches more than 95% in polarized light, which is well within the GRAVITY specifications.
Conclusions.
While integrated optics technology is known to be mature enough to provide efficient and reliable beam combiners for astronomical interferometry in the
H
band, we managed to successfully extend it to the longest wavelengths of the
K
band and to manufacture the most complex integrated optics beam combiner in this specific spectral band.
In this article, the model of swimming at low Reynolds number introduced by D. Takagi (2015) to analyze the displacement of an abundant variety of zooplankton is used as a testbed to analyze the ...motion of symmetric microswimmers in the framework of optimal control theory assuming that the motion occurs minimizing the energy dissipated by the fluid drag forces in relation with the concept of efficiency of a stroke. The maximum principle is used to compute periodic controls candidates as minimizing controls and is a decisive tool combined with appropriate numerical simulations using indirect optimal control schemes to determine the most efficient stroke compared with standard computations using Stokes theorem and curvature control. Also the concept of graded approximations in SR-geometry is used to evaluate strokes with small amplitudes providing a fixed displacement and minimizing the dissipated energy.
GRAVITY is the second generation Very Large Telescope Interferometer instrument for precision narrow-angle astrometry and interferometric imaging. With its fibre-fed integrated optics, wavefront ...sensors, fringe tracker, beam stabilisation and a novel metrology concept, GRAVITY will push the sensitivity and accuracy of astrometry and interferometric imaging far beyond what is offered today. Providing precision astrometry of order 10 microarcseconds, and imaging with 4-milliarcsecond resolution, GRAVITY will revolutionise dynamical measurements of celestial objects: it will probe physics close to the event horizon of the Galactic Centre black hole; unambiguously detect and measure the masses of black holes in massive star clusters throughout the Milky Way; uncover the details of mass accretion and jets in young stellar objects and active galactic nuclei; and probe the motion of binary stars, exoplanets and young stellar discs. The instrument capabilities of GRAVITY are outlined and the science opportunities that will open up are summarised.
This paper presents the design, technological realization, and characterization of a four telescopes combiner in silica on silicon integrated optics for Gravity. Complete work was performed through ...collaboration between CEA-LETI, IPAG, and CIP Technologies.
GRAVITY is an adaptive optics assisted Beam Combiner for the second generation VLTI instrumentation. The instrument will provide high-precision narrow-angle astrometry and phase-referenced ...interferometric imaging in the astronomical K-band for faint objects. We describe the wide range of science that will be tackled with this instrument, highlighting the unique capabilities of the VLTI in combination with GRAVITY. The most prominent goal is to observe highly relativistic motions of matter close to the event horizon of Sgr A*, the massive black hole at center of the Milky Way. We present the preliminary design that fulfils the requirements that follow from the key science drivers: It includes an integrated optics, 4-telescope, dual feed beam combiner operated in a cryogenic vessel; near-infrared wavefrontsensing adaptive optics; fringe-tracking on secondary sources within the field of view of the VLTI and a novel metrology concept. Simulations show that 10 {\mu}as astrometry within few minutes is feasible for a source with a magnitude of mK = 15 like Sgr A*, given the availability of suitable phase reference sources (mK = 10). Using the same setup, imaging of mK = 18 stellar sources in the interferometric field of view is possible, assuming a full night of observations and the corresponding UV coverage of the VLTI.
•The design of entire cropping systems to mitigate N leaching was tested.•Six cropping systems based on grain legumes and cover crops were compared during 6 years.•STICS was used to simulate water ...drainage and N leaching.•Grain-legume based rotations need to include cover crops to valorize N2 fixation and reduce nitrate leaching.
Grain legume-based cropping systems need to be designed holistically by taking profit of their advantages (e.g. symbiotic fixation of N2) while reducing environmental risks. In this experiment we studied the impact of the incorporation of cover crops in grain legume-based rotations on the mitigation of nitrate leaching and recycling of N for the subsequent cash crop. A cropping system experiment (2004–2010) with three 3-year rotations of different number of grain legumes (GL0, GL1 and GL2, none, one and two grain legumes, respectively) with (CC) or without (BF, bare fallow) cover crops was established at INRA Auzeville (SW France). Soil water and mineral N contents of the entire profile (0–120cm depth) were measured three times per season at key stages. Shoot cash and cover crop biomass and biomass N concentration were measured and the N acquisition of the different crops was calculated. In addition, the STICS soil–crop dynamic model was used to simulate the amount of daily water drained and N leached under the different rotations studied. STICS performed reasonably well when simulating soil water and soil nitrate contents, crop biomass and N acquired, allowing water drainage and nitrate leaching fluxes to be modelled with confidence. Globally, simulated N leaching was low due to amount of rainfall received during the experimental period which was lower than the 30-year average. As an average of the different crop sequences the cumulative N leaching during the experimental period (i.e. 2004–2010) increased when increasing the number of grain legumes in the rotation when no cover crops were used. However, the use of cover crops reduced N leaching. Within each rotation, cash crop N uptake did not differ between the BF and CC treatments. Our study highlights the importance of a proper design of entire cropping systems, i.e. simultaneously cash crop succession and cover crop, by adapting the crop rotation and the different management practices (i.e. N fertilization, irrigation, etc.) to mitigate the environmental impact of N leaching and reduce as much as possible pre-emptive competition phenomena due to cover crops.
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