Inertial Coupling Method for particles in an incompressible fluctuating fluid

We develop an inertial coupling method for modeling the dynamics of point-like 'blob' particles immersed in an incompressible fluid, generalizing previous work for compressible fluids. The coupling consistently includes excess (positive or negative) inertia of the particles relative to the displaced fluid, and accounts for thermal fluctuations in the fluid momentum equation. The coupling between the fluid and the blob is based on a no-slip constraint equating the particle velocity with the local average of the fluid velocity, and conserves momentum and energy. We demonstrate that the formulation obeys a fluctuation-dissipation balance, owing to the non-dissipative nature of the no-slip coupling. We develop a spatio-temporal discretization that preserves, as best as possible, these properties of the continuum formulation. In the spatial discretization, the local averaging and spreading operations are accomplished using compact kernels commonly used in immersed boundary methods. We find that the special properties of these kernels make the discrete blob a particle with surprisingly physically-consistent volume, mass, and hydrodynamic properties. We develop a second-order semi-implicit temporal integrator that maintains discrete fluctuation-dissipation balance, and is not limited in stability by viscosity. Furthermore, the temporal scheme requires only constant-coefficient Poisson and Helmholtz linear solvers, enabling a very efficient and simple FFT-based implementation on GPUs. We numerically investigate the performance of the method on several standard test problems...Comment: Contains a number of corrections and an additional Figure 7 (and associated discussion) relative to published versio

Hydrodynamics of Suspensions of Passive and Active Rigid Particles: A Rigid Multiblob Approach

We develop a rigid multiblob method for numerically solving the mobility problem for suspensions of passive and active rigid particles of complex shape in Stokes flow in unconfined, partially confined, and fully confined geometries. As in a number of existing methods, we discretize rigid bodies using a collection of minimally-resolved spherical blobs constrained to move as a rigid body, to arrive at a potentially large linear system of equations for the unknown Lagrange multipliers and rigid-body motions. Here we develop a block-diagonal preconditioner for this linear system and show that a standard Krylov solver converges in a modest number of iterations that is essentially independent of the number of particles. For unbounded suspensions and suspensions sedimented against a single no-slip boundary, we rely on existing analytical expressions for the Rotne-Prager tensor combined with a fast multipole method or a direct summation on a Graphical Processing Unit to obtain an simple yet efficient and scalable implementation. For fully confined domains, such as periodic suspensions or suspensions confined in slit and square channels, we extend a recently-developed rigid-body immersed boundary method to suspensions of freely-moving passive or active rigid particles at zero Reynolds number. We demonstrate that the iterative solver for the coupled fluid and rigid body equations converges in a bounded number of iterations regardless of the system size. We optimize a number of parameters in the iterative solvers and apply our method to a variety of benchmark problems to carefully assess the accuracy of the rigid multiblob approach as a function of the resolution. We also model the dynamics of colloidal particles studied in recent experiments, such as passive boomerangs in a slit channel, as well as a pair of non-Brownian active nanorods sedimented against a wall.Comment: Under revision in CAMCOS, Nov 201

Breaking Corn Yield Barriers: A Cropping Systems Approach

During 2015, four corn research trials were conducted in dryland and irrigated environments. Two trials were at Scandia, KS and two were in Topeka, KS. The objective of these trials was to study the contribution of different farming management approaches for developing efficient and high-yielding corn production systems. Treatment layout consisted of five combinations: common practices (CP), comprehensive fertilization (CF), production intensity (PI), ecological intensification (CF + PI), and advanced plus (AD). Under dryland and irrigation scenarios, EI and AD treatments presented the highest yields relative to the other combinations. Under irrigation, absolute yield gap was larger in both locations as compared to the dryland scenario. The EI and AP treatments produced better yields than all other treatments at all sites and water conditions

Breaking Soybean Yield Barriers: A Cropping Systems Approach

During 2015, four soybean research trials were conducted in dryland and irrigated environments. Two trials were at Scandia, KS, and two were in Topeka, KS. The objective of these trials was to study the contribution of different farming systems to developing efficient and high-yielding soybean production systems. Each experiment had five treatments: common practices (CP), comprehensive fertilization (CF), production intensity (PI), ecological intensification (CF + PI), and advanced plus (AD). Under dryland and irrigation EI and AD treatments had the maximum yield in both locations. Under irrigation, yield gap was the largest as compared to the dryland environment in both locations. In all four experiments common practices had the lowest yield

Breaking Corn Yield Barriers: A Cropping Systems Approach

A corn research trial was conducted at Scandia, KS, during the 2014 growing season. The objective was to study the contribution of different farming systems in developing efficient and high-yielding corn production systems. The experiment had five treatments: farmer practices, comprehensive fertilization, production intensity, ecological intensification, and advanced plus. Farmer practice was the lowest-yielding treatment, and ecological intensification and advanced plus treatment presented similar yields

Group V Phospholipase A2-Derived Lysophosphatidylcholine Mediates Cyclooxygenase-2 Induction in Lipopolysaccharide-Stimulated Macrophages

Producción CientíficaActivation of macrophages and macrophage cell lines by bacterial LPS elicits a delayed phase of PG biosynthesis that appears to be entirely mediated by cyclooxygenase-2 (COX-2). In previous work, we found that a catalytically active group V secreted phospholipase A2 (sPLA2-V) was required for COX-2 induction, but the nature of the sPLA2-V metabolite involved was not defined. In this study, we identify lysophosphatidylcholine (lysoPC) as the sPLA2-V downstream mediator involved in COX-2 induction by LPS-stimulated macrophages. Inhibition of sPLA2-V by RNA interference or by the cell-permeable compound scalaradial blocked LPS-induced COX-2 expression, and this inhibition was overcome by incubating the cells with a nonhydro- lyzable lysoPC analog, but not by arachidonic acid or oleic acid. Moreover, inhibition of sPLA2-V by scalaradial also prevented the activation of the transcription factor c-Rel, and such an inhibition was also selectively overcome by the lysoPC analog. Collectively, these results support a model whereby sPLA2-V hydrolysis of phospholipids upon LPS stimulation results in lysoPC generation, which in turn regulates COX-2 expression by a mechanism involving the transcriptional activity of c-Rel

Overexpression of cytosolic group IVA phospholipase A2 protects cells from Ca2+ -dependent death

El pdf del artículo es la versión post-print.-- et al.The calcium ionophore ionomycin induces apoptosis-like events in the human embryonic kidney cell line at early times. Plasma membrane blebbing, mitochondrial depolarization, externalization of phosphatidylserine, and nuclear permeability changes can all be observed within 15 min of treatment. However, there is no activation of caspases or chromatin condensation. Expression of a fusion protein containing the enhanced green fluorescent protein (EGFP) and human cytosolic Group IVA phospholipase A2α (EGFP-cPLA 2α) in these cells prevents ionomycin-induced phosphatidylserine externalization and death. Cells expressing the cPLA 2α mutant D43N, which does not bind calcium, retain their susceptibility to ionomycin-induced cell death. Both nonexpressing and EGFP-D43N-cPLA2α-expressing human embryonic kidney cells can be spared from ionomycin-induced cell death by pretreating them with exogenous arachidonic acid. Moreover, during calcium overload, mitochondrial depolarization is significantly lower in the EGFP-cPLA2α- expressing cells than in cells expressing normal amounts of cPLA 2α. These results suggest that early cell death events promoted by an overload of calcium can be prevented by the presence of high levels of arachidonic acid. © 2006 by The American Society for Biochemistry and Molecular Biology, Inc.This work was supported in part by Grant BMC2001- 2244 from the Spanish Ministry of Science and Technology, Grants BFU2004-01886/BMC, SAF2004-04676, and SAF2004-01232 from the Spanish Ministry of Education and Science, and Red Brucella, Red Respira, and Red Temática de Investigación Cardiovascular, from the Instituto de Salud Carlos III.Peer Reviewe

Drought-Tolerant Corn Hybrids Yield More in Drought-Stressed Environments with No Penalty in Non-stressed Environments

Citation: Adee, E., Roozeboom, K., Balboa, G. R., Schlegel, A., & Ciampitti, I. A. (2016). Drought-Tolerant Corn Hybrids Yield More in Drought-Stressed Environments with No Penalty in Non-stressed Environments. Frontiers in Plant Science, 7, 9. doi:10.3389/fpls.2016.01534The potential benefit of drought-tolerant (DT) corn (Zea mays L.) hybrids may depend on drought intensity, duration, crop growth stage (timing), and the array of drought tolerance mechanisms present in selected hybrids. We hypothesized that corn hybrids containing DT traits would produce more consistent yields compared to non-DT hybrids in the presence of drought stress. The objective of this study was to define types of production environments where DT hybrids have a yield advantage compared to non-DT hybrids. Drought tolerant and non-DT hybrid pairs of similar maturity were planted in six site-years with different soil types, seasonal evapotranspiration (ET), and vapor pressure deficit (VPD), representing a range of macro-environments. Irrigation regimes and seeding rates were used to create several micro-environments within each macro-environment. Hybrid response to the range of macro and micro-environmental stresses were characterized in terms of water use efficiency, grain yield, and environmental index. Yield advantage of DT hybrids was positively correlated with environment ET and VPD. Drought tolerant hybrids yielded 5 to 7% more than non-DT hybrids in high and medium ET environments (>430 mm ET), corresponding to seasonal VPD greater than 1200 Pa. Environmental index analysis confirmed that DT hybrids were superior in stressful environments. Yield advantage for DT hybrids appeared as yield dropped below 10.8 Mg ha(-1) and averaged as much as 0.6-1 Mg ha(-1) at the low yield range. Hybrids with DT technology can offer a degree of buffering against drought stress by minimizing yield reduction, but also maintaining a comparable yield potential in high yielding environments. Further studies should focus on the physiological mechanisms presented in the commercially available corn drought tolerant hybrids

Closing Corn Yield Gaps via Improved Management: A Systems Approach

Three corn research trials were conducted during the 2016 growing season. Two studies were conducted at Scandia, KS, (dryland and irrigated) and one at Topeka, KS (dryland). The objective of these trials was to investigate the contribution of different farming systems for closing corn yield gaps. Each experiment consisted of five treatments: common practices (CP), comprehensive fertilization (CF), production intensity (PI), ecological intensification (CF + PI), and advanced plus (AD). Across all three experiments and under dryland and irrigation scenarios, CP presented the lowest yield. In environments with yield response, intensifying production without a balanced nutrition program did not increase yields. A balanced nutrition program substantially increased yields in corn with more relative impact in dryland environments. The absolute yield gap was 86 bu/a for dryland and 75 bu/a for irrigated condition