Effects of the MV Rena oil spill on intertidal rocky reefs in the Bay of Plenty,New Zealand

In the weeks following the 2011 Rena oil spill, a series of surveys was initiated on eight rocky intertidal reefs to describe the distribution of oil and to assess the impacts of oil on ecological communities. Consistent but relatively low cover of oil occurred at two sites (Mt Maunganui and Moturiki). The area covered by oil had decreased by c. 90% after 5 months due to natural weathering processes. There were immediate effects of oil fouling on the mussel Limnoperna pulex and its associated fauna, with reductions in the number of mussels and infaunal taxonomic richness. However, no ecological effects on any of the communities were detectable after 1 month. Overall, the ecological effects of the Rena oil spill on rocky shore intertidal communities were small and not long-lasting, but we stress that this does not consider potential sublethal effects and their consequences on organisms.     

Le zooplancton du lac de Bret en 1902/03, 1943 et 1951

Summary The Lac de Bret, formerly an “oligotrophic” lake, has by several artificial risings of its level become “eutrophic” with the drawbacks of that state during the summer stagnation. A plant of partial underwater aeration has improved the situation and has been described in this Review (11, 423 [1949]). The above study compares the zooplancton of this lake in the years 1902/03 when it was yet oligotrophic with its plancton in the year 1943 during the investigations in the lake become eutrophic and finally in the year 1951 when it had again grown sound after five seasons of estival acration.      

Recherches hydrobiologiques au lac de barrage de Barberine (Valais)

Sans résumé Avec 2 illustrations     

Comparative analysis of Venus and Mars magnetotails

We have an unique opportunity to compare the magnetospheres of two non-magnetic planets as Mars and Venus with identical instrument sets Aspera-3 and Aspera-4 on board of the Mars Express and Venus Express missions. We have performed both statistical and case studies of properties of the magnetosheath ion flows and the flows of planetary ions behind both planets. We have shown that the general morphology of both magnetotails is generally identical. In both cases the energy of the light (H⁺) and the heavy (O⁺, etc.) ions decreases from the tail periphery (several keV) down to few eV in the tail center. At the same time the wake center of both planets is occupied by plasma sheet coincident with the current sheet of the tail. Both plasma sheets are filled by accelerated (500-1000 eV) heavy planetary ions. We report also the discovery of a new feature never observed before in the tails of non-magnetic planets: the plasma sheet is enveloped by consecutive layers of He⁺ and H⁺ with decreasing energies.     

The calibration of the Cassini-Huygens CAPS Electron Spectrometer

We present the two-stage method used to calibrate the electron spectrometer (ELS), part of the plasma spectrometer (CAPS) on board the Cassini spacecraft currently in orbit around Saturn. The CAPS-ELS is a top-hat electrostatic analyser designed to measure electron fluxes between 0.5 eV and 26 keV. The on-ground calibration method described here includes the production of photoelectrons, which are energised and passed into the CAPS-ELS in a purpose designed calibration facility. Knowledge of the intensity of these incident electrons and the subsequent instrument output provides an on-ground calibrated geometric factor. Comparative studies of physical quantities such as plasma density and electron differential flux calculated using on-ground calibration factor with the quantities deduced from the wave experiment and high energy electron detector provide in-flight calibration. The results of this are presented together with a comparison of the experimentally calibrated values with simulated calibration values.     

40Ar39Ar dating of glauconites: Measured 39Ar recoil loss from well-crystallized specimens

Nine glauconite samples with relatively high K concentrations and which appear to be well crystallized using normal X-ray diffraction techniques have been studied using the ${}^{40}\text{Ar}{}^{39}\text{Ar}$ method. The glauconite ${}^{40}\text{Ar}{}^{39}\text{Ar}$ apparent ages exceed their KAr, RbSr and, in most cases, stratigraphic ages by substantial amounts. ${}^{40}\text{Ar}{}^{39}\text{Ar}$ release spectra sometimes yield plateaus but these apparent ages have no geological significance. The results indicate that ³⁹Ar is lost by recoil from mineral grains during neutron irradiation, consistent with previously reported observations. The amount of ³⁹Ar loss was measured by isotope dilution for four samples and varied from 29% to 17%. In contrast, radiogenic ⁴⁰Ar is quantitatively retained during irradiation. The very fine blades which make up glauconite grains yield the mineral susceptible to large amounts of ³⁹Ar loss and unsuitable for ${}^{40}\text{Ar}{}^{39}\text{Ar}$ dating.     

First ENA observations at Mars: Charge exchange ENAs produced in the magnetosheath

Measurements of energetic neutral atoms (ENA) generated in the magnetosheath at Mars are reported. These ENAs are the result of charge exchange collisions between solar wind protons and neutral oxygen and hydrogen in the exosphere of Mars. The peak of the observed ENA flux is . For the case studied here, i.e., the passage of Mars Express through the martian magnetosheath around 20:15 UT on 3 May 2004, the measurements agree with an analytical model of the ENA production at the planet. It is possible to find parameter values in the model such that the observed peak in the ENA count rate during the spacecraft passage through the magnetosheath is reproduced.     

The massive star binary fraction in young open clusters – I. NGC 6231 revisited

We present the results of a long-term high-resolution spectroscopy campaign on the O-type stars in NGC 6231. We revise the spectral classification and multiplicity of these objects and we constrain the fundamental properties of the O-star population. Almost three quarters of the O-type stars in the cluster are members of a binary system. The minimum binary fraction is 0.63, with half the O-type binaries having an orbital period of the order of a few days. The eccentricities of all the short-period binaries are revised downward, and henceforth match a normal period–eccentricity distribution. The mass ratio distribution shows a large preference for O + OB binaries, ruling out the possibility that, in NGC 6231, the companion of an O-type star is randomly drawn from a standard initial mass function. Obtained from a complete and homogeneous population of O-type stars, our conclusions provide interesting observational constraints to be confronted with the formation and early evolution theories of O-stars.