Hydrodynamics of hypersonic jets: experiments and numerical simulations

Stars form in regions of the galaxy that are denser and cooler than the mean interstellar medium. These regions are called Giant Molecular Clouds. At the beginning of their life, up to 10⁵–10⁶ years, stars accrete matter from their rich surrounding environment and are origin of a peculiar phenomenon that is the jet emission. Jets from Young Stellar Objects (YSOs) are intensively studied by the astrophysical community by observations at different wavelengths, analytical and numerical modeling and laboratory experiments. Indications about the jet propagation and its resulting morphologies are here obtained by means of a combined study of hypersonic jets carried out both in the laboratory and by numerical simulations.     

Interplanetary dust detected by the Cassini CDA Chemical Analyser

During its cruise phase, prior to encountering Jupiter, the Cosmic Dust Analyser (CDA) onboard the Cassini spacecraft returned time of flight mass spectra (TOF MS) of two interplanetary dust particles. Both particles were found to be iron-rich, with possible traces of hydrogen, carbon, nickel, chromium, manganese, titanium, vanadium and minor silicates. Carbon, hydrogen, oxygen and potassium are also present as possible contaminants of the impact target of CDA. Silicates and magnesium do not feature predominantly in the spectra; this is surprising considering the expected dominance of silicate-rich minerals in interplanetary dust particles. The particle masses are and . The corresponding radii ranges for the particles, assuming densities from 7874-2500 kg m⁻³ are 0.7-4 μm and 2.6-6.8 μm, respectively. With the same density assumptions the β values (ratio of radiation pressure to gravitational force) are estimated as 0.027-0.21 and 0.016-0.06 respectively, allowing possible orbits to be calculated. The resulting orbits are bound and prograde with semi-major axes, eccentricities and inclinations in the region of 0.3-1.26 AU, 0.4-1.0 and 0-60° for the first particle and 0.8-2.5 AU, 0.2-0.9 and 0-30° for the second. The more probable orbits within these ranges indicate that the first particle is in an Aten-like orbit, whilst the second particle is in an Apollo-like orbit, despite both grains having very similar, predominantly metallic compositions. Other possible orbital solutions for both particles encompass orbits which more closely resemble those of Jupiter-family comets.     

Validation of boundary layer parameters of climate model REMO: estimation of leaf area index from NOAA-AVHRR data for the Baltimos region

The preparation of time- and space-dependent input surface parameters for the climate model REMO was one task of the Baltimos project “Validation of Boundary Layer Parameters and Extension of Boundary conditions of Climate Model REMO”. The leaf area index (LAI) is one of these parameters. It is used in REMO as defined value per month for each land-use class with a defined seasonal trend during the year. Since 1982 at the Institute of Meteorology of the Free University Berlin, a high-resolved AVHRR data set of the NOAA satellite has been available (1/100 degree, approximately 1?×?1 km at nadir in a geographic coordination system) (Koslowsky 1996). The vegetation periods of the years 1997 until 2001 were selected from the dataset to estimate the LAI within the Baltimos region on the basis of an algorithm by Sellers et al. (J Climate 9:706–737, 1996) and a modified United States Geological Survey (USGS) land-use classification. The calculated high-resolved NOAA LAI values were converted to the 1/6 degree grid of the REMO climate model. Then, they were compared to the fixed LAI values, which are used in the model.     

Temperature-sensitive line ratios of the lithium-like ion O vi

During the past decade a number of instruments designed for studying solar oscillations have been developed at the Sayan observatory. A double solar telescope using two Jensch-coelostats and two objective lenses provides the capability to filter lower-order modes. This instrument is also used (in the single-telescope mode) for making observations of the mean magnetic field of the Sun. Spatially-differential methods based on polarization separation of images are best suited for investigations of local oscillations and higher-order modes. These methods make it possible to carry out narrow-band spatial filtering of large wave numbers. They are useful when investigating contrast oscillations as well as the oscillations and rotation of sunspots and other solar features.     

The evolution of spokes in Saturn's B ring

The optical appearance of spokes was studied in high resolution (?200 km/lp) images obtained by Voyager 2. Spokes are classified into three categories. (1) Extended spokes are seen in the distance interval of 100,000 to 112,000 km from Saturn's center. They have diffuse edges and are slightly wedge shaped. Their width at the base (towards Saturn) is about 20,000 km. Their active times (during which they increase in width) range from 4000 to 12,000 sec. (2) Narrow spokes are found in the distance range 104,000 to 116,000 km, have sharply defined edges, and are narrowest at the corotation distance (112, 300 km). Their typical radial extension and width is 6000 and 2,000 km, respectively. (3) Filamentary spokes are found outside 110,000 km mostly joined with a wider spoke further in. They are typically 3000 km in length and 500 km in width. Their active time is less than 1000 sec. Several narrow spokes were observed during formation along radial lines in the sunlit portion of the ring. The formation time is typically ?5 min for a 6000-km-long spoke. The rate of spoke formation is highest at the morning ansa outside Saturn's shadow. Several spokes have been found where one edge revolves with Keplerian speed whereas the other edge stays radial. Recurrent spoke patterns have been observed at the period of Saturn's rotation. From edge-on views of the ring system, an upper limit for the height of spokes of 80 km is derived.     

Evidence for beamed electrons in a limb X-ray flare observed by HXIS

X-ray images taken by the Hard X-Ray Imaging Spectrometer (HXIS) aboard SMM during the 1980, November 18 limb flare are analysed. The temporal and spatial evolutions of the X-radiation are described. They differ significantly for hard and soft X-rays. During the elementary flare bursts energetic photons are predominantly emitted from a region close to the solar limb. In contrast, the soft X-ray sources are situated higher in the solar atmosphere. The observed X-ray spectra, in particular those emitted from small source regions at various altitudes, were fitted to power laws. Analysis of the spatial variation of the spectral index shows that there is a systematic tendency of the spectra to get harder with decreasing source altitude, especially during the elementary flare bursts. This fact is in agreement with the existence of nonthermal electron beams precipitating from the corona towards the denser layers of the solar atmosphere.     

Evaluating the Global Environment Facility: A goodwill gesture or a serious attempt to deliver global benefits?

Over its 17 years, the UN's Global Environment Facility (GEF) has allocated US $7.5 billion intended to develop and implement scientifically and socially credible solutions to key global environmental problems such as climate change, biological diversity loss and degradation of transboundary aquatic systems. We studied 906 GEF projects to analyse the challenges that it is facing in delivering solutions that are likely to be sustainable in the long-term. The research included desk reviews of relevant documents and follow-up interviews with a wide range of stakeholders. Some of the challenges the GEF faces are deeply rooted in temporal and spatial mismatches of scale between human economies and their environmental consequences and the strongly sectoral way current society is managed. We conclude that the GEF obtained impressive results for tackling problems of limited complexity and easily quantified benefits but progress is slower on more complex and less tangible problems impeding sustainable development. Potentially, the GEF could enable adaptive management through a ‘learning by doing’ process, transforming it into an innovative mechanism for delivering global benefits. Continued emphasis on ‘easy wins’ would not allow it to achieve this goal.     

Sample return of interstellar matter (SARIM)

The scientific community has expressed strong interest to re-fly Stardust-like missions with improved instrumentation. We propose a new mission concept, SARIM, that collects interstellar and interplanetary dust particles and returns them to Earth. SARIM is optimised for the collection and discrimination of interstellar dust grains. Improved active dust collectors on-board allow us to perform in-situ determination of individual dust impacts and their impact location. This will provide important constraints for subsequent laboratory analysis. The SARIM spacecraft will be placed at the L2 libration point of the Sun–Earth system, outside the Earth’s debris belts and inside the solar-wind charging environment. SARIM is three-axes stabilised and collects interstellar grains between July and October when the relative encounter speeds with interstellar dust grains are lowest (4 to 20 km/s). During a 3-year dust collection period several hundred interstellar and several thousand interplanetary grains will be collected by a total sensitive area of 1 m². At the end of the collection phase seven collector modules are stored and sealed in a MIRKA-type sample return capsule. SARIM will return the capsule containing the stardust to Earth to allow for an extraction and investigation of interstellar samples by latest laboratory technologies.     

DuneXpress

The DuneXpress observatory will characterize interstellar and interplanetary dust in-situ, in order to provide crucial information not achievable with remote sensing astronomical methods. Galactic interstellar dust constitutes the solid phase of matter from which stars and planetary systems form. Interplanetary dust, from comets and asteroids, represents remnant material from bodies at different stages of early solar system evolution. Thus, studies of interstellar and interplanetary dust with DuneXpress in Earth orbit will provide a comparison between the composition of the interstellar medium and primitive planetary objects. Hence DuneXpress will provide insights into the physical conditions during planetary system formation. This comparison of interstellar and interplanetary dust addresses directly themes of highest priority in astrophysics and solar system science, which are described in ESA’s Cosmic Vision. The discoveries of interstellar dust in the outer and inner solar system during the last decade suggest an innovative approach to the characterization of cosmic dust. DuneXpress establishes the next logical step beyond NASA’s Stardust mission, with four major advancements in cosmic dust research: (1) analysis of the elemental and isotopic composition of individual interstellar grains passing through the solar system, (2) determination of the size distribution of interstellar dust at 1 AU from 10^− 14 to 10^− 9 g, (3) characterization of the interstellar dust flow through the planetary system, (4) establish the interrelation of interplanetary dust with comets and asteroids. Additionally, in supporting the dust science objectives, DuneXpress will characterize dust charging in the solar wind and in the Earth’s magnetotail. The science payload consists of two dust telescopes of a total of 0.1 m² sensitive area, three dust cameras totaling 0.4 m² sensitive area, and a nano-dust detector. The dust telescopes measure high-resolution mass spectra of both positive and negative ions released upon impact of dust particles. The dust cameras employ different detection methods and are optimized for (1) large area impact detection and trajectory analysis of submicron sized and larger dust grains, (2) the determination of physical properties, such as flux, mass, speed, and electrical charge. A nano-dust detector searches for nanometer-sized dust particles in interplanetary space. A plasma monitor supports the dust charge measurements, thereby, providing additional information on the dust particles. About 1,000 grains are expected to be recorded by this payload every year, with 20% of these grains providing elemental composition. During the mission submicron to micron-sized interstellar grains are expected to be recorded in statistically significant numbers. DuneXpress will open a new window to dusty universe that will provide unprecedented information on cosmic dust and on the objects from which it is derived.     

德国南部索伦霍芬石板印灰岩中翼龙纤维状头骨脊连续矿物化的证据

The Solnhofen Lithographic Limestone and other Upper Jurassic “Solnhofen type” plattenkalks of southeast Germany are famous for pterosaur fossils with soft tissue preservation. Flight membranes, integumentary structures such as pedal scales and bristles as well as pedal webbing are known from these deposits.