We use measurements from the Rosetta plasma consortium Langmuir probe and mutual impedance probe to study the spatial distribution of low‐energy plasma in the near‐nucleus coma of comet 67P/Churyumov‐Gerasimenko. The spatial distribution is highly structured with the highest density in the summer hemisphere and above the region connecting the two main lobes of the comet, i.e., the neck region. There is a clear correlation with the neutral density and the plasma to neutral density ratio is found to be ∼1–2·10−6, at a cometocentric distance of 10 km and at 3.1 AU from the Sun. A clear 6.2 h modulation of the plasma is seen as the neck is exposed twice per rotation. The electron density of the collisionless plasma within 260 km from the nucleus falls off with radial distance as ∼1/r. The spatial structure indicates that local ionization of neutral gas is the dominant source of low‐energy plasma around the comet.

Supercritical carbon dioxide (scCO 2 ) has been investigated for the generation of valuable waxy compounds and as an added-value technology in a holistic maize stover biorefinery. ScCO 2 extraction and fractionation was carried out prior to hydrolysis and fermentation of maize stover. Fractionation of the crude extracts by scCO 2 resulted in wax extracts having different compositions and melting temperatures, enabling their utilisation in different applications. One such fraction demonstrated significant potential as a renewable defoaming agent in washing machine detergent formulations. Furthermore, scCO 2 extraction has been shown to have a positive effect on the downstream processing of the maize stover. Fermentation of the scCO 2 extracted maize stover hydrolysates exhibited a higher glucose consumption and greater potential growth for surfactant (in comparison with non-scCO 2 treated stover) and ethanol production (a 40% increase in overall ethanol production after scCO 2 pre-treatment). This work represents an important development in the extraction of high value components from low value wastes and demonstrates the benefits of using scCO 2 extraction as a first-step in biomass processing, including enhancing downstream processing of the biomass for the production of 2 nd generation biofuels as part of an integrated holistic biorefinery.

The Radio and Plasma Waves (RPW) instrument on the ESA Solar Orbiter mission is described in this paper. This instrument is designed to measure in-situ magnetic and electric fields and waves from the continuous to a few hundreds of kHz. RPW will also observe solar radio emissions up to 16 MHz. The RPW instrument is of primary importance to the Solar Orbiter mission and science requirements since it is essential to answer three of the four mission overarching science objectives. In addition RPW will exchange on-board data with the other in-situ instruments in order to process algorithms for interplanetary shocks and type III langmuir waves detections.

The abundance of exoplanets with orbits smaller than that of Mercury most likely implies that there are exoplanets exposed to a quasiparallel stellar-wind magnetic field. Many of the generic features of stellar-wind interaction depend on the existence of a nonzero perpendicular interplanetary magnetic field component. However, for closer orbits the perpendicular component becomes smaller and smaller. The resulting quasiparallel interplanetary magnetic field may imply new types of magnetospheres and interactions not seen in the solar system. We simulate the Venus-like interaction between a supersonic stellar wind and an Earth-sized, unmagnetized terrestrial planet with ionosphere, orbiting a Sun-like star at 0.2 AU. The importance of a quasiparallel stellar-wind interaction is then studied by comparing three simulation runs with different angles between stellar wind direction and interplanetary magnetic field. The plasma simulation code is a hybrid code, representing ions as particles and electrons as a massless, charge-neutralizing adiabatic fluid. Apart from being able to observe generic features of supersonic stellar-wind interaction we observe the following changes and trends when reducing the angle between stellar wind and interplanetary magnetic field 1) that a large part of the bow shock is replaced by an unstable quasiparallel bow shock; 2) weakening magnetic draping and pile-up; 3) the creation of a second, flanking current sheet due to the need for the interplanetary magnetic field lines to connect to almost antiparallel draped field lines; 4) stellar wind reaching deeper into the dayside ionosphere; and 5) a decreasing ionospheric mass loss. The speed of the last two trends seems to accelerate at low angles.

Cloud compression by external shocks is believed to be an important triggering mechanism for gravitational collapse and star formation in the interstellar medium. We have performed MHD simulations to investigate whether the radiative interaction between a shock wave and a small interstellar cloud can induce the conditions for Jeans instability and how the interaction is influenced by magnetic fields of different strengths and orientation. The simulations use the NIRVANA code in three dimensions with anisotropic heat conduction and radiative heating/cooling at an effective resolution of 100 cells per cloud radius. Our cloud has radius 1.5 pc, has density 17 cm −3 , is embedded in a medium of density 0.17 cm −3 , and is struck by a planar Mach 30 shock wave. The simulations produce dense, cold fragments similar to those of Mellema et al. and Fragile et al. We do not find any regions that are Jeans unstable but do record transient cloud density enhancements of factors ∼10 3 -10 5 for the bulk of the cloud mass, which then decline and converge toward seemingly stable net density enhancement factors ∼10 2 -10 4 . Our run with a weak, initial magnetic field (β = 10 3 ) perpendicular to the shock normal stands out as producing the most lasting density enhancements. We interpret this field strength as being the compromise between weak internal magnetic pressure preventing compression and sufficiently strong magnetic field to thermally insulate the condensations, thus helping them cool radiatively.

Aims. The aim of this work is to demonstrate that the probe-to-spacecraft potential measured by RPW on Solar Orbiter can be used to derive the plasma (electron) density measurement, which exhibits both a high temporal resolution and a high level of accuracy. To investigate the physical nature of the solar wind turbulence and waves, we analyze the density and magnetic field fluctuations around the proton cyclotron frequency observed by Solar Orbiter during the first perihelion encounter (∼0.5 AU away from the Sun). Methods. We used the plasma density based on measurements of the probe-to-spacecraft potential in combination with magnetic field measurements by MAG to study the fields and density fluctuations in the solar wind. In particular, we used the polarization of the wave magnetic field, the phase between the compressible magnetic field and density fluctuations, and the compressibility ratio (the ratio of the normalized density fluctuations to the normalized compressible fluctuations of B) to characterize the observed waves and turbulence. Results. We find that the density fluctuations are 180° out of phase (anticorrelated) with the compressible component of magnetic fluctuations for intervals of turbulence, whereas they are in phase for the circular-polarized waves. We analyze, in detail, two specific events with a simultaneous presence of left- and right-handed waves at different frequencies. We compare the observed wave properties to a prediction of the three-fluid (electrons, protons, and alphas) model. We find a limit on the observed wavenumbers, 10−6 < k < 7 × 10−6 m−1, which corresponds to a wavelength of 7 × 106 > λ > 106 m. We conclude that it is most likely that both the left- and right-handed waves correspond to the low-wavenumber part (close to the cut-off at ΩcHe + +) of the proton-band electromagnetic ion cyclotron (left-handed wave in the plasma frame confined to the frequency range ΩcHe + + < ω < Ωcp) waves propagating in the outwards and inwards directions, respectively. The fact that both wave polarizations are observed at the same time and the identified wave mode has a low group velocity suggests that the double-banded events occur in the source regions of the waves.

BackgroundContamination of bacteria in large-scale yeast fermentations is a serious problem and a threat to the development of successful biofuel production plants. Huge research efforts have been spent in order to solve this problem, but additional ways must still be found to keep bacterial contaminants from thriving in these environments. The aim of this project was to develop process conditions that would inhibit bacterial growth while giving yeast a competitive advantage.ResultsLactic acid bacteria are usually considered to be the most common contaminants in industrial yeast fermentations. Our observations support this view but also suggest that acetic acid bacteria, although not so numerous, could be a much more problematic obstacle to overcome. Acetic acid bacteria showed a capacity to drastically reduce the viability of yeast. In addition, they consumed the previously formed ethanol. Lactic acid bacteria did not show this detrimental effect on yeast viability. It was possible to combat both types of bacteria by a combined addition of NaCl and ethanol to the wood hydrolysate medium used. As a result of NaCl + ethanol additions the amount of viable bacteria decreased and yeast viability was enhanced concomitantly with an increase in ethanol concentration. The successful result obtained via addition of NaCl and ethanol was also confirmed in a real industrial ethanol production plant with its natural inherent yeast/bacterial community.ConclusionsIt is possible to reduce the number of bacteria and offer a selective advantage to yeast by a combined addition of NaCl and ethanol when cultivated in lignocellulosic medium such as wood hydrolysate. However, for optimal results, the concentrations of NaCl + ethanol must be adjusted to suit the challenges offered by each hydrolysate.

The atmospheres of close-in extrasolar planets are expected to both undergo hydrodynamic expansion due to strong heating and produce strong expanding ionospheres due to intense photoionization, while at the same time being exposed to strong stellar winds. This scenario can be expected to lead to new types of magnetospheres and previously unseen interactions between stellar wind plasma and ionospheres. Our aim is to start looking at these kinds of scenarios for close-in terrestrial planets using hybrid simulations. For this purpose we used a hybrid code, treating electrons as a massless, charge-neutralizing, adiabatic fluid and ions as macroparticles, to study the influence of a strongly expanding ionosphere on the stellar wind interaction for an unmagnetized close-in extrasolar terrestrial planet. For both with and without expansion, we can identify bow shock, magnetopause, and ion-composition boundary. The expanding ionosphere pushes the bow shock, magnetic draping, and ion composition boundary upstream and increases the size of the entire interaction region, creating a large wake behind the planet, largely void of electromagnetic fields and dominated only by the expanding ionosphere. On the dayside, little ionospheric radial bulk flow is actually observed since the ions are quickly thermalized after being added to the ionosphere.