An efficient parallel immersed boundary algorithm using a pseudo-compressible fluid solver

We propose an efficient algorithm for the immersed boundary method on distributed-memory architectures, with the computational complexity of a completely explicit method and excellent parallel scaling. The algorithm utilizes the pseudo-compressibility method recently proposed by Guermond and Minev [Comptes Rendus Mathematique, 348:581-585, 2010] that uses a directional splitting strategy to discretize the incompressible Navier-Stokes equations, thereby reducing the linear systems to a series of one-dimensional tridiagonal systems. We perform numerical simulations of several fluid-structure interaction problems in two and three dimensions and study the accuracy and convergence rates of the proposed algorithm. For these problems, we compare the proposed algorithm against other second-order projection-based fluid solvers. Lastly, the strong and weak scaling properties of the proposed algorithm are investigated

WAMDII observation of an auroral atmosphere wave event

Field tests of WAMDII (Wide Angle Michelson Doppler Imaging Interferometer) on February 23 to 24, 1984 in Saskatoon produced wind images of the aurora that show well defined wave structures in lambda 5577. Wavelengths and velocities of these structures suggest an acoustic-gravity wave interpretation, but their short duration warrants their being termed an event. The Dopplergrams are presented with emphasis on the interpretation of the waves and a discussion of possible sources

Cell cycle-dependent phosphorylation of Theileria annulata schizont surface proteins

The invasion of Theileria sporozoites into bovine leukocytes is rapidly followed by the destruction of the surrounding host cell membrane, allowing the parasite to establish its niche within the host cell cytoplasm. Theileria infection induces host cell transformation, characterised by increased host cell proliferation and invasiveness, and the activation of anti-apoptotic genes. This process is strictly dependent on the presence of a viable parasite. Several host cell kinases, including PI3-K, JNK, CK2 and Src-family kinases, are constitutively activated in Theileria-infected cells and contribute to the transformed phenotype. Although a number of host cell molecules, including IkB kinase and polo-like kinase 1 (Plk1), are recruited to the schizont surface, very little is known about the schizont molecules involved in host-parasite interactions. In this study we used immunofluorescence to detect phosphorylated threonine (p-Thr), serine (p-Ser) and threonine-proline (p-Thr-Pro) epitopes on the schizont during host cell cycle progression, revealing extensive schizont phosphorylation during host cell interphase. Furthermore, we established a quick protocol to isolate schizonts from infected macrophages following synchronisation in S-phase or mitosis, and used mass spectrometry to detect phosphorylated schizont proteins. In total, 65 phosphorylated Theileria proteins were detected, 15 of which are potentially secreted or expressed on the surface of the schizont and thus may be targets for host cell kinases. In particular, we describe the cell cycle-dependent phosphorylation of two T. annulata surface proteins, TaSP and p104, both of which are highly phosphorylated during host cell S-phase. TaSP and p104 are involved in mediating interactions between the parasite and the host cell cytoskeleton, which is crucial for the persistence of the parasite within the dividing host cell and the maintenance of the transformed state

Brightness variations of the northern 630nm intertropical arc and the midnight pressure bulge over Eritrea

The nightglow brightness at 630nm from the thermospheric O(<sup>1</sup>D) layer was monitored nightly at Asmara, Eritrea (15.4° N, 39.9° E, 7° N dip) with an all-sky imager. Averages of north-south strips of the images enabled contour plots of brightness on a latitude vs. local time grid. The contours show the movement of the intertropical arc southward before midnight, staying just north of Asmara after midnight, and gradually brightening to a maximum at 02:00h local civil time, 02:00 LT, after which it disappears before dawn. It is argued that all features of the plots can be explained by known mechanisms capable of driving ions along magnetic field lines, including the fountain effect, summer to winter transequatorial winds, and the midnight pressure bulge. <P style="line-height: 20px;"> The 02:00 LT brightness maximum is the most striking and the most persistent feature in the data. The persistence of the location of the 02:00 LT brightening is attributed to a pressure bulge centered on the geographic equator at midnight and extending to higher latitudes with increasing local time in both the winter and the summer hemispheres. The bulge is shown to be stronger near solstice than near equinox, confirming earlier work

Genesis capsule yields solar wind samples

NASA's Genesis capsule, carrying the first samples ever returned from beyond the Moon, took a hard landing in the western Utah desert on 8 September after its parachutes failed to deploy Despite the impact, estimated at 310 km per hour, some valuable solar wind collector materials have been recovered. With these samples, the Genesis team members are hopeful that nearly all of the primary science goals may be met. The Genesis spacecraft was launched in August 2001 to collect and return samples of solar wind for precise isotopic and elemental analysis. The spacecraft orbited the Earth-Sun Lagrangian point (LI), ˜1.5 million km sunward of Earth, for 2.3 years. It exposed ultrapure materials—including wafers of silicon, silicon carbide, germanium, chemically deposited diamond, gold, aluminum, and metallic glass— to solar wind ions, which become embedded within the substrates' top 100 nm of these materials

Constraints on the Mode and Extent of Sedimentary Rock Alteration in Hyper-Arid and Hypo-Thermal Environments

Geologic evidence suggests that the surface of Mars has been dominated by cold, dry, and relatively stable environmental conditions over the past ~3.5 Ga. These conditions differ from those pre-sumed to be present prior to ~3.5 Ga, when observa-tions indicate that the martian surface was at least in-termittently able to support the prolonged flow of liq-uid water. Despite the more than 75% of martian his-tory dominated by cold, dry, and stable conditions, few investigations have studied weathering and alteration processes that may influence the martian surface dur-ing this time. Please see attachment

Fractionation of MG Isotopes between the Sun’s Photosphere and the Solar Wind

The Genesis mission goal is to precisely determine the elemental and isotopic composition of the solar photosphere through measurements of solar wind; the photospheric composition being a proxy for the early solar nebula. So, how elements and isotopes are fractionated (or not) when accelerated out of the photosphere is fundamental to interpreting Genesis data

Reconciling mantle attenuation-temperature relationships from seismology, petrology, and laboratory measurements

Seismic attenuation measurements provide a powerful tool for sampling mantle properties. Laboratory experiments provide calibrations at seismic frequencies and mantle temperatures for dry melt-free rocks, but require ∼10²−10³ extrapolations in grain size to mantle conditions; also, the effects of water and melt are not well understood. At the same time, body wave attenuation measured from dense broadband arrays provides reliable estimates of shear wave attenuation (Q_S⁻¹), affording an opportunity for calibration. We reanalyze seismic data sets that sample arc and back-arc mantle in Central America, the Marianas, and the Lau Basin, confirming very high attenuation (Q_S ∼ 25–80) at 1 Hz and depths of 50–100 km. At each of these sites, independent petrological studies constrain the temperature and water content where basaltic magmas last equilibrated with the mantle, 1300–1450°C. The Q_S measurements correlate inversely with the petrologically inferred temperatures, as expected. However, dry attenuation models predict Q_S too high by a factor of 1.5–5. Modifying models to include effects of H₂O and rheology-dependent grain size shows that the effects of water-enhanced dissipation and water-enhanced grain growth nearly cancel, so H₂O effects are modest. Therefore, high H₂O in the arc source region cannot explain the low Q_S, nor in the back arc where lavas show modest water content. Most likely, the high attenuation reflects the presence of melt, and some models of melt effects come close to reproducing observations. Overall, body wave Q_S can be reconciled with petrologic and laboratory inferences of mantle conditions if melt has a strong influence beneath arcs and back arcs