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| 2. |
- Appeltans, W., et al.
(författare)
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The Magnitude of Global Marine Species Diversity
- 2012
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Ingår i: Current Biology. - : Elsevier BV. - 0960-9822 .- 1879-0445. ; 22:23, s. 2189-2202
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Tidskriftsartikel (refereegranskat)abstract
- Background: The question of how many marine species exist is important because it provides a metric for how much we do and do not know about life in the oceans. We have compiled the first register of the marine species of the world and used this baseline to estimate how many more species, partitioned among all major eukaryotic groups, may be discovered. Results: There are similar to 226,000 eukaryotic marine species described. More species were described in the past decade (similar to 20,000) than in any previous one. The number of authors describing new species has been increasing at a faster rate than the number of new species described in the past six decades. We report that there are similar to 170,000 synonyms, that 58,000-72,000 species are collected but not yet described, and that 482,000-741,000 more species have yet to be sampled. Molecular methods may add tens of thousands of cryptic species. Thus, there may be 0.7-1.0 million marine species. Past rates of description of new species indicate there may be 0.5 +/- 0.2 million marine species. On average 37% (median 31%) of species in over 100 recent field studies around the world might be new to science. Conclusions: Currently, between one-third and two-thirds of marine species may be undescribed, and previous estimates of there being well over one million marine species appear highly unlikely. More species than ever before are being described annually by an increasing number of authors. If the current trend continues, most species will be discovered this century.
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| 3. |
- Bradley, L. E., et al.
(författare)
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Effect of laser temporal intensity skew on enhancing pair production in laser-electron-beam collisions
- 2021
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Ingår i: New Journal of Physics. - : IOP Publishing. - 1367-2630. ; 23:9
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Tidskriftsartikel (refereegranskat)abstract
- Recent high-intensity laser experiments (Cole et al 2018 Phys. Rev. X 8 011020; Poder et al 2018 Phys. Rev. X 8 031004) have shown evidence of strong radiation reaction in the quantum regime. Experimental evidence of quantum effects on radiation reaction and electron-positron pair cascades has, however, proven challenging to obtain and crucially depends on maximising the quantum parameter of the electron (defined as the ratio of the electric field it feels in its rest frame to the Schwinger field). The quantum parameter can be suppressed as the electrons lose energy by radiation reaction as they traverse the initial rise in the laser intensity. As a result the shape of the intensity temporal envelope becomes important in enhancing quantum radiation reaction effects and pair cascades. Here we show that a realistic laser pulse with a faster rise time on the leading edge, achieved by skewing the temporal envelope, results in curtailing of pair yields as the peak power is reduced. We find a reduction in pair yields by orders of magnitude in contrast to only small reductions reported previously in large-scale particle-in-cell code simulations (Hojbota et al 2018 Plasma Phys. Control. Fusion 60 064004). Maximum pairs per electron are found in colliding 1.5 GeV electrons with a laser wakefield produced envelope 7.90 x 10(-2) followed by a short 50 fs Gaussian envelope, 1.90 x 10(-2), while it is reduced to 8.90 x 10(-5), a factor of 100, for an asymmetric envelope.
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| 4. |
- Metson, Genevieve, 1988-, et al.
(författare)
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Phosphorus in Phoenix : a budget and spatial representation of phosphorus in an urban ecosystem
- 2012
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Ingår i: Ecological Applications. - : John Wiley & Sons. - 1051-0761 .- 1939-5582. ; 22:2, s. 705-721
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Tidskriftsartikel (refereegranskat)abstract
- As urban environments dominate the landscape, we need to examine how limiting nutrients such as phosphorus (P) cycle in these novel ecosystems. Sustainable management of P resources is necessary to ensure global food security and to minimize freshwater pollution. We used a spatially explicit budget to quantify the pools and fluxes of P in the Greater Phoenix Area in Arizona, USA, using the boundaries of the Central Arizonaï¿œPhoenix Long-Term Ecological Research site. Inputs were dominated by direct imports of food and fertilizer for local agriculture, while most outputs were small, including water, crops, and material destined for recycling. Internally, fluxes were dominated by transfers of food and feed from local agriculture and the recycling of human and animal excretion. Spatial correction of P dynamics across the city showed that human density and associated infrastructure, especially asphalt, dominated the distribution of P pools across the landscape. Phosphorus fluxes were dominated by agricultural production, with agricultural soils accumulating P. Human features (infrastructure, technology, and waste management decisions) and biophysical characteristics (soil properties, water fluxes, and storage) mediated P dynamics in Phoenix. P cycling was most notably affected by water management practices that conserve and recycle water, preventing the loss of waterborne P from the ecosystem. P is not intentionally managed, and as a result, changes in land use and demographics, particularly increased urbanization and declining agriculture, may lead to increased losses of P from this system. We suggest that city managers should minimize cross-boundary fluxes of P to the city. Reduced P fluxes may be accomplished through more efficient recycling of waste, therefore decreasing dependence on external nonrenewable P resources and minimizing aquatic pollution. Our spatial approach and consideration of both pools and fluxes across a heterogeneous urban ecosystem increases the utility of nutrient budgets for city managers. Our budget explicitly links processes that affect P cycling across space with the management of other resources (e.g., water). A holistic management strategy that deliberately couples the management of P and other resources should be a priority for cities in achieving urban sustainability.
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| 5. |
- Altavilla, A., et al.
(författare)
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Impact of the new european paediatric regulatory framework on ethics committees: overview and perspectives
- 2012
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Ingår i: Acta Paediatrica. - : Wiley. - 1651-2227 .- 0803-5253. ; 101:1
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Tidskriftsartikel (refereegranskat)abstract
- Aim: To evaluate the impact of the new European paediatric regulatory framework on the activities of Ethics Committees operating in Europe and to assess their involvement and interest in paediatric research. Methods: Task-force in Europe for Drug Development for the Young Network of Excellence and Relating Expectations and Needs to the Participation and Empowerment of Children in Clinical Trials project set up an inventory of Ethics Committees existing in Europe and conducted a survey on their approach to paediatric trials. Results: Ethics Committees operating in 22 European Countries participated in this survey. Results showed a high lack of knowledge, understanding and awareness of the current European paediatric regulatory framework and a lack of involvement of Ethics Committees in paediatric research, especially in terms of training and education, demonstrated also by the decreasing number of Ethics Committees answering exhaustively to the whole questionnaire. The majority of participating Ethics Committees expressed interest in future initiatives related to paediatric research. Conclusions: Despite a limited knowledge and understanding of the current paediatric regulatory framework, a significant number of Ethics Committees operating in Europe show interest in initiatives related to paediatric research. Networking may be an essential tool to be used to enhance Ethics Committees role in supporting paediatric research. Any initiative should be undertaken at European level in collaboration with European Union Institutions.
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| 6. |
- Galletti, L., et al.
(författare)
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Influence of topological edge states on the properties of Al/Bi2Se3/Al hybrid Josephson devices
- 2014
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Ingår i: Physical Review B - Condensed Matter and Materials Physics. - 2469-9950 .- 2469-9969. ; 89:13
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Tidskriftsartikel (refereegranskat)abstract
- In superconductor-topological insulator-superconductor hybrid junctions, the barrier edge states are expected to be protected against backscattering, to generate unconventional proximity effects, and, possibly, to signal the presence of Majorana fermions. The standards of proximity modes for these types of structures have to be settled for a neat identification of possible new entities. Through a systematic and complete set of measurements of the Josephson properties we find evidence of ballistic transport in coplanar Al-Bi2Se3-Al junctions that we attribute to a coherent transport through the topological edge state. The shunting effect of the bulk only influences the normal transport. This behavior, which can be considered to some extent universal, is fairly independent of the specific features of superconducting electrodes. A comparative study of Shubnikov-de Haas oscillations and scanning tunneling spectroscopy gave an experimental signature compatible with a two-dimensional electron transport channel with a Dirac dispersion relation. A reduction of the size of the Bi2Se3 flakes to the nanoscale is an unavoidable step to drive Josephson junctions in the proper regime to detect possible distinctive features of Majorana fermions.
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| 7. |
- Ghaemi, Hirad, 1980, et al.
(författare)
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CLEAN technique in strip-map SAR for high-quality imaging
- 2009
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Ingår i: IEEE Aerospace Conference Proceedings. - 1095-323X. - 9781424426225 ; , s. Art. no. 4839474-
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Konferensbidrag (refereegranskat)abstract
- The maximum obtainable resolution of a strip-map synthetic aperture radar (SAR) system can be retained by simply avoiding weighting, or tapering, data samples in the along-track compression process. However, this will lead to hazardous artifacts caused by strong sidelobes of the corresponding adjacent scatterers whose interference might severely weaken the desired targets or even introduce false targets. On the other hand, some residual artifacts, even after tapering process, may still deteriorate the quality (contrast) of the SAR image. These issues can be remedied by applying the so-called CLEAN technique, which can mitigate these ill-effects in strip-map SAR imagery while maintaining the maximum resolution. This, indeed, is carried out as a post processing step, i.e., after the azimuth compression is accomplished, in the SAR system. The objective of this paper is to extend the CLEAN technique to strip-map SAR system to produce high-quality images with a very good along-track resolution. The algorithm is then applied to data from a ground-based circular SAR (CSAR) system to verify its implementation as well as this new application of the CLEAN technique.
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| 8. |
- Ghaemi, Hirad, 1980, et al.
(författare)
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RELAX-based autofocus algorithm for high-resolution strip-map SAR
- 2009
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Ingår i: IEEE National Radar Conference - Proceedings. - 1097-5659. - 9781424428717 ; , s. 1 - 6
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Konferensbidrag (refereegranskat)abstract
- This paper addresses the non-iterative quality phase gradient autofocus (QPGA) technique which was originally proposed to remove one-dimensional phase errors in spotlight-mode synthetic aperture radar (SAR) imagery. By enriching the source pool, the method is modified in a way suitable for autofocus in stripmap-mode SAR system with the advantage of being independent of any priori assumptions. Unlike the QPGA the potential candidates, i.e., dominant scatterers located along azimuth in each specific range bin, are automatically selected by exploiting the one-dimensional RELAX algorithm. Furthermore, RELAX is capable of estimating the size of blur window which is, in fact, associated with the Doppler spread of signal spectrum. The corresponding model includes four parameters i.e., complex amplitude, delay, Doppler center and spectral width. The proposed method has been applied to data extracted by a ground-based rotating coherent Doppler radar operating in strip-mapping mode SAR, with the aim of high-resolution clutter detection.
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| 9. |
- Razmadze, D., et al.
(författare)
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Supercurrent reversal in ferromagnetic hybrid nanowire Josephson junctions
- 2023
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Ingår i: Physical Review B. - 2469-9950. ; 107:8
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Tidskriftsartikel (refereegranskat)abstract
- We report supercurrent transport measurements in hybrid Josephson junctions comprising semiconducting InAs nanowires with epitaxial ferromagnetic insulator EuS and superconducting Al coatings. The wires display a hysteretic superconducting window close to the coercivity, away from zero external magnetic field. Using a multi-interferometer setup, we measure the current-phase relation of multiple magnetic junctions and find an abrupt switch between π and 0 phases within the superconducting window. We attribute the 0-π transition to the discrete flipping of the EuS domains and provide a qualitative theory showing that a sizable exchange field can polarize the junction and lead to the supercurrent reversal. Both 0 and π phases can be realized at zero external field by demagnetizing the wire.
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| 10. |
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