An experimental study of rip channel flow

A laboratory study of the flow over a bar with a single rip channel has been performed. First, the well-known pattern of a bar circulation cell with a strong offshore-directed current out through the rip channel and a weaker onshore-directed return flow over the bar is documented. Then measurements of the three-dimensional structure of the flow in the area where the rip channel, the bar and the trough meet and well inside the rip channel are presented. These measurements reveal that 3D effects play an important role, and that a depth-integrated viewpoint may not always be sufficient for predicting the flow in the near bed region. Particle-tracking experiments illustrate the near bed flow pattern over the entire area. These demonstrate how the overall trajectory pattern changes as a function of the distance of wave breaking from the bar crest: For some conditions, the rip current is fed from the trough and for other conditions it is fed directly from the bar. Both the 3D measurements and the trajectory tests show the existence of a weaker onshore-directed near-bed drift in the area where the rip current ceases. Finally, in a series of sensitivity tests, measurements of the rip current intensity for different wave climate and water level conditions reveal a strong correlation between the rip current intensity and the wave height (both normalized).     

The production of cosmogenic nuclides in stony meteoroids by galactic cosmic‐ray particles

Abstract— We present a purely physical model for the calculation of depth‐ and size‐dependent production rates of cosmogenic nuclides by galactic cosmic‐ray (GCR) particles. besides the spectra of primary and secondary particles and the excitation functions of the underlying nuclear reactions, the model is based on only one free parameter—the integral number of gcr particles in the meteoroid orbits. We derived this value from analysis of radionuclide data in Knyahinya. We also show that the mean GCR proton spectrum in the meteoroid orbits has been constant over about the last 10 Ma. For the major target elements in stony meteoroids, we present depth‐ and size‐dependent production rates for ¹⁰Be, ¹⁴C, ²⁶Al, ³⁶Cl, and ⁵³Mn as well as for the rare gas isotopes ³He, ²⁰Ne, ²¹Ne, ²²Ne, ³⁶Ar, and ³⁸Ar. The new data differ from semi‐empirical estimates by up to a factor of 4 but agree within ～20% with results obtained by earlier parametric or physical approaches. The depth and size dependence of the shielding parameter ²²Ne/²¹Ne and the correlations ²⁶Al vs. ¹⁰Be, ²⁶Al vs. ⁵³Mn, ¹⁰Be/²¹Ne vs. ²²Ne/²¹Ne, and ³⁶Ar vs. ³⁶Cl for deciphering preatmospheric sizes, shielding depths, terrestrial residence times, and exposure histories are also discussed.     

Active Galactic Nuclei

D01 Direct evidence of the receding ‘torus’ around active galactic nuclei of FRII radio galaxies and quasars D02 Infrared emission from a clumpy and dusty torus around AGN D03 Size and properties of AGN narrow–line regions from emission–line diagnostics D04 Structural Variability of Intraday Variable Sources D05 Stability of self‐gravitating accretion disks in galactic centers D06 Supermassive Binary Black Holes in AGN D07 The extreme flare in III Zw 2: Evolution of a radio jet in a Seyfert galaxy D08 Radio Linear and Circular Polarization from M81* D09 A fundamental relation between Supermassive Black Holes and Dark Matter Haloes D10 Hunting for radio‐quiet BL Lacs – the 2dF BL Lac survey D11 The Eddington limit in accretion discs D12 Molecular Tori in AGN: A search using excited states of OH D13 The X‐Ray Properties of Radio‐Loud Core‐Dominated AGN: The 2 cm‐X‐Sample D14 The X‐Ray Properties of Radio‐Loud Core‐Dominated AGN: Extension to the High Redshift Regime D15 Line Profile Variability in AGN D16 Jet Superwind Interaction D17 Radio Interferometric Observations of AGN – Probing the Nucleus of M87 with 20 Schwarzschild radii resolution D18 The ISO–2MASS AGN survey D19 Supermassive binary black holes driving the activity of galactic nuclei D20 Proton acceleration at quasi‐perpendicular shocks: A case study for Active Galactic Nuclei D21 Super‐luminal shocks in Active Galactic Nuclei D22 Unconventional quasars from the variability and proper motion survey D23 Radio observations of starburst and AGN activity in Ultraluminous Infrared Galaxies D24 Kinematics in Active Galactic Nuclei at Parsec Scales: the VLBA 2cm Survey D25 Three‐dimensional models of clumpy tori in Seyfert galaxies D26 Silicate emission in active galaxies ‐ From LINERs to QSOs D27 Discovery of 10 µm silicate emission in quasars. – Evidence of the AGN unification scheme. D28 Near‐IR adaptive optics imaging of luminous infrared galaxies D29 Interferometric observations of the Circinus galaxy with MIDI D30 Infrared Interferometry of the Seyfert Galaxy NGC 1068     

The science process for selecting the landing site for the 2011 Mars Science Laboratory

The process of identifying the landing site for NASA’s 2011 Mars Science Laboratory (MSL) began in 2005 by defining science objectives, related to evaluating the potential habitability of a location on Mars, and engineering parameters, such as elevation, latitude, winds, and rock abundance, to determine acceptable surface and atmospheric characteristics. Nearly 60 candidate sites were considered at a series of open workshops in the years leading up to the launch. During that period, iteration between evolving engineering constraints and the relative science potential of candidate sites led to consensus on four final sites. The final site will be selected in the Spring of 2011 by NASA’s Associate Administrator for the Science Mission Directorate. This paper serves as a record of landing site selection activities related primarily to science, an inventory of the number and variety of sites proposed, and a summary of the science potential of the highest ranking sites.     

Sedimentary Trace Elements as Proxies to Depositional Changes Induced by a Holocene Fresh-Brackish Water Transition

A halocline developed in the GotlandDeep, Baltic Sea, at c. 8.0 ¹⁴C ky BP, as theresult of a transition from fresh to brackish water.The sediment-water interface changed from oxic topredominantly anoxic, depositional conditions wereperiodically euxinic and pyrite formation wasextensive. This environmental change led topyritization of the upper part of earlier depositedsediments. This study discusses how the distributionof trace elements (As, Ba, Cd, Cu, Co, Mo, Mn, Ni, Pb,U, Zn and V) were affected by the changing redoxconditions, productivity and salinity. The reducingconditions led to pyritization of Cu, Co, Ni, Cd, Mo,Mn and As. Lead and Zn concentrations are very low inpyrite, in agreement with their coordination tosulfide being tetrahedral. Certain elements areenriched in those sediments deposited under euxinicconditions. This enrichment was caused by scavengingof elements dissolved in the water column and isrestricted to elements that have a comparably longresidence time in the Baltic Sea. Molybdenum appearsto be the most unambigious proxy for euxinicconditions, whereas enrichment of U also requiresbrackish water in the productive zone. In the brackishenvironment, enrichment of Ba and V are linked to thecycling of organic carbon. Manganese and As are theonly elements that have been significantly remobiliseddue to the downward moving pyritization front.     

Importance of sulfate emission to sulfur deposition at urban and rural sites in China

Throughfall (TF) and wet only (WO) deposition along with SO₂ and sulfate (SO₄²⁻) concentration in air at 4 urban and rural sites in southwestern China were monitored in order to understand the role of different forms of sulfur (S) emission to the S deposition and its effect in China. The sites were located in Chongqing, Hunan, and Guizhou provinces. S deposition at the most polluted site reached 15 g S m^− 2 yr^− 1. At three of the sites, located in the vicinity of several emission sources, dry S deposition is 2.1–4.2 times that of wet deposition, which is significantly higher than what is found in most other parts of the world.Main components in airborne particles (PM₁₀) are (NH₄)₂SO₄ and CaSO₄ at the highly polluted Tie Shan Ping (TSP) site. Dust particles of gypsum (CaSO₄) in the air are partly due to direct emission and partly from the reaction of calcium oxides and carbonates with sulfuric acid in the air. To illustrate the importance of sulfate emission to total S deposition we analyzed the source of S deposition based on both measurements and models. Results indicated that direct emission of SO₄²⁻ particles could account for high proportion in total S deposition at the three most polluted sites.     

Oceanic Velocity Microstructure Measurements in the 20th Century

The science of ocean turbulence was started more than 50 years ago by a small research group using a surplus mine-sweeping paravane to measure the velocity and temperature fluctuations in the ocean. The field has grown considerably and measurements are now conducted by researchers in many countries. A wide variety of sophisticated instrument systems are used to profile horizontally and vertically through the marine environment. Here we review the historical development of velocity micro-structure profiles over the past four decades and summarize the basic requirements for successful measurements. We highlight critical technological developments and glance briefly at some of the scientific discoveries made with these instruments. This revised version was published online in August 2006 with corrections to the Cover Date.     

Cenozoic intra-plate magmatism in the Darfur volcanic province: mantle source, phonolite-trachyte genesis and relation to other volcanic provinces in NE Africa

Chemical and Sr, Nd and Pb isotopic compositions of Late Cenozoic to Quaternary small-volume phonolite, trachyte and related mafic rocks from the Darfur volcanic province/NW-Sudan have been investigated. Isotope signatures indicate variable but minor crustal contributions. Some phonolitic and trachytic rocks show the same isotopic composition as their primitive mantle-derived parents, and no crustal contributions are visible in the trace element patterns of these samples. The magmatic evolution of the evolved rocks is dominated by crystal fractionation. The Si-undersaturated strongly alkaline phonolite and the Si-saturated mildly alkaline trachyte can be modelled by fractionation of basanite and basalt, respectively. The suite of basanite–basalt–phonolite–trachyte with characteristic isotope signatures from the Darfur volcanic province fits the compositional features of other Cenozoic intra-plate magmatism scattered in North and Central Africa (e.g., Tibesti, Maghreb, Cameroon line), which evolved on a lithosphere that was reworked or formed during the Neoproterozoic.     

What can we Expect from a New Radio Telescope in Upper Egypt?

The selection criteria for the project of a new radio telescope in Egyptare described. The telescope will have a diameter of 32 m and will belocated in Abu Simbel (Upper Egypt). One major task of the telescope isthe participation in VLBI network operation.