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With the recent discovery of a dozen dusty star-forming galaxies and around 30 quasars at z > 5 that are hyper-luminous in the infrared (μ LIR > 1013 L⊙, where μ is a lensing magnification factor), the possibility has opened up for SPICA, the proposed ESA M5 mid-/far-infrared mission, to extend its spectroscopic studies toward the epoch of reionisation and beyond. In this paper, we examine the feasibility and scientific potential of such observations with SPICA’s far-infrared spectrometer SAFARI, which will probe a spectral range (35–230 μm) that will be unexplored by ALMA and JWST. Our simulations show that SAFARI is capable of delivering good-quality spectra for hyper-luminous infrared galaxies at z = 5 − 10, allowing us to sample spectral features in the rest-frame mid-infrared and to investigate a host of key scientific issues, such as the relative importance of star formation versus AGN, the hardness of the radiation field, the level of chemical enrichment, and the properties of the molecular gas. From a broader perspective, SAFARI offers the potential to open up a new frontier in the study of the early Universe, providing access to uniquely powerful spectral features for probing first-generation objects, such as the key cooling lines of low-metallicity or metal-free forming galaxies (fine-structure and H2 lines) and emission features of solid compounds freshly synthesised by Population III supernovae. Ultimately, SAFARI’s ability to explore the high-redshift Universe will be determined by the availability of sufficiently bright targets (whether intrinsically luminous or gravitationally lensed). With its launch expected around 2030, SPICA is ideally positioned to take full advantage of upcoming wide-field surveys such as LSST, SKA, Euclid, and WFIRST, which are likely to provide extraordinary targets for SAFARI.
Our current global food system – from food production to consumption, including manufacture, packaging, transport, retail and associated businesses – is responsible for extensive negative social and environmental impacts which threaten the long-term well-being of society. This has led to increasing calls from science–policy organizations for major reform and transformation of the global food system. However, our knowledge regarding food system transformations is fragmented and this is hindering the development of co-ordinated solutions. Here, we collate recent research across several academic disciplines and sectors in order to better understand the mechanisms that ‘lock-in’ food systems in unsustainable states.
Tidal flexure in ice shelf grounding zones has been used extensively in the past to determine grounding line position and ice properties. Although the rheology of ice is viscoelastic at tidal loading frequencies, most modelling studies have assumed some form of linear elastic beam approximation to match observed flexure profiles. Here we use density, radar and DInSAR measurements in combination with full-Stokes viscoelastic modelling to investigate a range of additional controls on the flexure of the Southern McMurdo Ice Shelf. We find that inclusion of observed basal crevasses and density dependent ice stiffness can greatly alter the flexure profile and yet fitting a simple elastic beam model to that profile will still produce an excellent fit. Estimates of the effective Young's modulus derived by fitting flexure profiles are shown to vary by over 200% depending on whether these factors are included, even when the local thickness is well constrained. Conversely, estimates of the grounding line position are relatively insensitive to these considerations for the case of a steep bed slope in our study region. By fitting tidal amplitudes only, and ignoring phase information, elastic beam theory can provide a good fit to observations in a wide variety of situations. This should, however, not be taken as an indication that the underlying rheological assumptions are correct.
Africa is experiencing a rapid increase in adult obesity and associated cardiometabolic diseases (CMDs). The H3Africa AWI-Gen Collaborative Centre was established to examine genomic and environmental factors that influence body composition, body fat distribution and CMD risk, with the aim to provide insights towards effective treatment and intervention strategies. It provides a research platform of over 10 500 participants, 40–60 years old, from Burkina Faso, Ghana, Kenya and South Africa. Following a process that involved community engagement, training of project staff and participant informed consent, participants were administered detailed questionnaires, anthropometric measurements were taken and biospecimens collected. This generated a wealth of demographic, health history, environmental, behavioural and biomarker data. The H3Africa SNP array will be used for genome-wide association studies. AWI-Gen is building capacity to perform large epidemiological, genomic and epigenomic studies across several African counties and strives to become a valuable resource for research collaborations in Africa.
D. R. Viete, G. J. H. Oliver and S. A. Wilde comment: First, we would like to commend Aoki et al. (2013) on a careful study and thought-provoking manuscript. Their interpretation of the Barrovian metamorphism as a fundamentally retrograde feature offers a refreshing alternative to the more conventional ‘peak-metamorphic’ models.
Atomic force microscopy (AFM) can be combined with fluorescence microscopy to measure the changes in intracellular calcium levels (indicated by fluorescence of Ca2+ sensitive dye fluo-4) in response to mechanical stimulation performed by AFM. Mechanical stimulation using AFM is associated with cantilever movement, which may interfere with the fluorescence signal. The motion of the AFM cantilever with respect to the sample resulted in changes of the reflection of light back to the sample and a subsequent variation in the fluorescence intensity, which was not related to changes in intracellular Ca2+ levels. When global Ca2+ responses to a single stimulation were assessed, the interference of reflected light with the fluorescent signal was minimal. However, in experiments where local repetitive stimulations were performed, reflection artifacts, correlated with cantilever motion, represented a significant component of the fluorescent signal. We developed a protocol to correct the fluorescence traces for reflection artifacts, as well as photobleaching. An added benefit of our method is that the cantilever reflection in the fluorescence recordings can be used for precise temporal correlation of the AFM and fluorescence measurements.
The UK was one of few European countries to document a substantial wave of pandemic (H1N1) 2009 influenza in summer 2009. The First Few Hundred (FF100) project ran from April–June 2009 gathering information on early laboratory-confirmed cases across the UK. In total, 392 confirmed cases were followed up. Children were predominantly affected (median age 15 years, IQR 10–27). Symptoms were mild and similar to seasonal influenza, with the exception of diarrhoea, which was reported by 27%. Eleven per cent of all cases had an underlying medical condition, similar to the general population. The majority (92%) were treated with antiviral drugs with 12% reporting adverse effects, mainly nausea and other gastrointestinal complaints. Duration of illness was significantly shorter when antivirals were given within 48 h of onset (median 5 vs. 9 days, P=0·01). No patients died, although 14 were hospitalized, of whom three required mechanical ventilation. The FF100 identified key clinical and epidemiological characteristics of infection with this novel virus in near real-time.
The Outer Hebrides Fault Zone is a major easterly dipping reactivated shear zone which displaces Lewisian gneiss of the Laurentian craton, NW Scotland. Despite a number of detailed field studies, the fault zone remains poorly understood with regard to both its age of inception and precise conditions of reactivation. The island of Scalpay in the northern portion of the Outer Hebrides Fault Zone provides exceptional exposures through a variety of reactivated fault rock types and therefore represents an ideal location to investigate fault zone evolution via fluid inclusion studies of syn-tectonic quartz veins. This fluid inclusion study constrains reactivation temperatures more precisely than hitherto possible with top-to-the-NW ductile thrusting occurring at 500 ± 30°C. Subsequent phyllonitization is associated with oblique sinistral top-to-the-NE strike-slip at 230 ± 20°C, followed by a discrete system of top-to-the-NE/SE extensional detachments at 150 ± 20°C. Other recent fluid inclusion studies in the southern portion of the Outer Hebrides Fault Zone constrain phyllonitization associated with top-to-the-E displacement to 370 ± 20°C, with subsequent top-to-the-NE extensional detachments operating at 150–210°C. Thus, late-stage extensional detachment systems record consistent conditions of reactivation along the strike length of the Outer Hebrides Fault Zone. However, our results also clearly emphasize that conditions of earlier fault zone reactivation and phyllonitization were highly heterogeneous between the northern and southern portions, thus suggesting a spatial and temporal variation in the deformation and/or fluid flux system.
We have analysed a rare occurrence of orange-brown manganotantalite lamellae (visible in hand specimen), intergrown with microlite [(Ca,Na)2(Ta,Nb)2(O,OH,F)7], aggregates of ferrotapiolite, bismuth minerals and apatite to understand more about the mechanisms of crystal growth and secondary modification in Ta-rich minerals. The intergrowth occurs within amblygonite/montebrasite nodules near the quartz core of the highly fractionated rare-metal Li/Be/Ta pegmatite at Rubicon, Karibib, Namibia. Electron microprobe analyses show that manganotantalite lamellae are variable in composition. Primary microlite (Ta2O5 82%, 1.97 Ta a.p.f.u.) forms the matrix mineral between the lamellae. Textural relations suggest an exsolution origin for the lamellae. Manganotantalite is represented by three generations: (1) primary late magmatic; (2) disequilibrium exsolution lamellae; and (3) subsolidus replacement. Crystallization commenced with primary microlite and likely simultaneous intergrowth between ferrotapiolite and a first generation of late-magmatic primary manganotantalite with low Ta (1.1—1.5 a.p.f.u.). On cooling this was followed by exsolution of manganotantalite lamellae, generation (2) with low—medium Ta (1.27—1.7 a.p.f.u.). The replacement of microlite by a highly fractionated late-stage melt rich in Mn2+, Ca2+ with low Na+ finally produces a third generation (3) of manganotantalite with high Ta (1.72—1.99 a.p.f.u.) at the contact with microlite. Native bismuth and bismutite cut across microlite and pseudomorph lamellae as a final hydrothermal replacement. Apatite is ubiquitous at the contact with amblygonite. The stability field of microlite may be extended by incorporation of CaTa2O6-rynersonite and Ca2Ta2O7 — idealized, components in solid solution. However, rynersonite-CaTa2O6 with distorted octahedra has some structural templates which are similar to the structure of pyrochlore (microlite). Hence, via the perovskite/pyrochlore analogy, hypothetical exsolution of manganotantalite-type structures may occur from a microlite (pyrochlore) host by solid-state diffusion via metastable rynersonite-type intermediates. Such a mechanism has the potential to explain the crystallographically controlled intergrowth textures and the compositional heterogeneity.
This paper addresses scientific and technological efforts to develop highly efficient silicon thin film solar modules on glass substrates. We present a comprehensive study of μc-Si:H p-i-n single junction and a-Si:H/μc-Si:H stacked solar cells prepared by plasma-enhanced chemical vapour deposition (PECVD) at 13.56 MHz excitation frequency. In the first step cell development was performed in a small area PECVD reactor showing the relationship between deposition process and resulting solar cell performance. Subsequent up-scaling to a substrate area of 30×30 cm2 confirmed the scalability to large area reactors. Moreover, we developed textured ZnO:Al films by sputtering and post deposition wet chemical etching as front contact TCO-material with excellent light scattering properties. A-Si:H/μc-Si:H tandem cells developed on this textured ZnO yielded stable efficiencies up to 11.2 % for a cell area of 1 cm2. First solar modules were prepared in our recently installed process technology, which includes PECVD, sputtering, texture etching and laser scribing on substrate sizes up to 30x30 cm2. Initial module efficiencies of 10.8 % and 10.1 % were achieved for aperture areas of 64 cm2 and 676 cm2, respectively.
Al-doped ZnO films were deposited on glass in an in-line system by reactive mid-frequency (MF) magnetron sputtering. The influence of substrate position on the film properties as well as the relation between static and dynamic deposition are studied. All films showed low resistivity (<4x10-4 Ωcm) and excellent transparency (> 80 % in the visible region). The resistivity ρ for substrate positions above the sputter craters (race tracks) is up to a factor of two higher than on other positions where the smallest ρ is 1.9 x 10-4 Ωcm. Major differences in statically deposited films as a function of the position on the substrate are found for the structural film properties as characterized by x-ray diffraction (XRD) and etching behaviour. The different surface textures obtained after etching are directly related to variations in the short-circuit current densities of amorphous silicon p-i-n solar cells prepared on these etched ZnO:Al films.
The Outer Hebrides Fault Zone is a major ESE-dipping reactivated structure within
Lewisian basement gneisses of the Laurentian craton, northwest Scotland. Detailed mapping in South
Uist reveals important new evidence that contributes to a better understanding of the kinematic evolution
of the fault zone. Large quantities of pseudotachylite which characterize the fault zone on South
Uist may in part be lithologically controlled, and therefore of little value in determining areas of greatest
deformation and displacement. Only limited evidence is preserved for ductile and brittle thrust-sense
movements along this portion of the fault zone. The tectonics of the fault zone on South Uist are
dominated by structures associated with several episodes of pervasive top-down-to-the-SE to -ENE
brittle extensional deformation, which are progressively overprinted by protophyllonitic and phyllonitic
fabrics associated with top-down-to-the-E to -ENE extension. A series of late-stage high-angle
normal faults record top-down-to-the-ESE to -ENE extension and cut the phyllonites. Fluid inclusion
studies from syntectonic quartz veins constrain the conditions of phyllonite formation at 370 ± 20 °C.
Field evidence suggests that this section of the Outer Hebrides Fault Zone may have been largely unaffected
by sinistral strike-slip reactivation as reported along-strike to the north, suggesting both a varied
and compartmentalized tectonic and evolutionary history along the length of the Outer Hebrides
Replacement phenomena in amblygonite–montebrasite in rare-element pegmatites from the Karibib-Usakos area, Namibia, have been investigated using the electron microprobe. The first African occurrence and analysis of the very rare mineral natromontebrasite NaAl(PO4)(OH,F) is reported from the Daheim pegmatite. In the Okatjimukuju pegmatite, montebrasite has been replaced by a number of phases including crandallite CaAl3(PO4)2(OH)5·H2O and brazilianite NaAl3(PO4)2(OH)4. In one example, montebrasite has been almost completely replaced by brazilianite which has also been found to contain not only crandallite but also its solid solution analogues: goyazite SrAl3(PO4)2(OH)5·H2O and gorceixite BaAl3(PO4)2(PO3OH)(OH)6. Apatite is common at the contacts with montebrasite and associated minerals and texturally is intimately intergrown with crandallite, goyazite and gorceixite at Okatjimukuju. The occurrence of these minerals offers insight into the chemistry of post-magmatic fluids in these pegmatites.