| 1. |
- Hickler, Thomas, et al.
(författare)
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Precipitation controls Sahel greening trend
- 2005
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Ingår i: Geophysical Research Letters. - 1944-8007. ; 32:21
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Tidskriftsartikel (refereegranskat)abstract
- The Sahel region has been identified as a "hot spot'' of global environmental change, but understanding of the roles of different climatic and anthropogenic forcing factors driving change in the region is incomplete. We show that a process-based ecosystem model driven by climatic and atmospheric CO2 data alone closely reproduces the satellite-observed greening trend of the Sahel vegetation and its interannual variability between 1982 and 1998. Changes in precipitation were identified as the primary driver of the aggregated simulated vegetation changes. According to the model, the increasing carbon uptake through vegetation was associated with an increasing relative carbon sink; but integrated over the whole period, the Sahel was predicted to be a net source of carbon.
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| 2. |
- Jakobsson, Martin, et al.
(författare)
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Potential links between Baltic Sea submarine terraces and groundwater seeping
- 2020
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Ingår i: Earth Surface Dynamics. - : Copernicus GmbH. - 2196-6311 .- 2196-632X. ; 8:1, s. 1-15
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Tidskriftsartikel (refereegranskat)abstract
- Submarine groundwater discharge (SGD) influences ocean chemistry, circulation, and the spreading of nutrients and pollutants; it also shapes sea floor morphology. In the Baltic Sea, SGD was linked to the development of terraces and semicircular depressions mapped in an area of the southern Stockholm archipelago, Sweden, in the 1990s. We mapped additional parts of the Stockholm archipelago, areas in Blekinge, southern Sweden, and southern Finland using high-resolution multibeam sonars and sub-bottom profilers to investigate if the sea floor morphological features discovered in the 1990s are widespread and to further address the hypothesis linking their formation to SGD. Sediment coring and sea floor photography conducted with a remotely operated vehicle (ROV) and divers add additional information to the geophysical mapping results. We find that terraces, with general bathymetric expressions of about 1 m and lateral extents of sometimes > 100 m, are widespread in the surveyed areas of the Baltic Sea and are consistently formed in glacial clay. Semicircular depressions, however, are only found in a limited part of a surveyed area east of the island of Asko, southern Stockholm archipelago. While submarine terraces can be produced by several processes, we interpret our results to be in support of the basic hypothesis of terrace formation initially proposed in the 1990s; i.e. groundwater flows through siltier, more permeable layers in glacial clay to discharge at the sea floor, leading to the formation of a sharp terrace when the clay layers above seepage zones are undermined enough to collapse. By linking the terraces to a specific geologic setting, our study further refines the formation hypothesis and thereby forms the foundation for a future assessment of SGD in the Baltic Sea that may use marine geological mapping as a starting point. We propose that SGD through the submarine sea floor terraces is plausible and could be intermittent and linked to periods of higher groundwater levels, implying that to quantify the contribution of freshwater to the Baltic Sea through this potential mechanism, more complex hydrogeological studies are required.
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| 3. |
- Lewis, Jeffrey, et al.
(författare)
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PFAS – A threat for groundwater and drinking water supply in Sweden?
- 2015
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Ingår i: EGU General Assembly 2015. ; 17
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Perfluoroalkyl substances (PFAS) are a group of anthropogenic environmental pollutants that are widely distributed in the global environment. They have multiple industrial uses, including water repellents in clothing, paper coatings and firefighting foam. According to a study released by the Environmental Directorate of the OECD, they are persistent, bioaccumulative and toxic to mammalian species (OECD, 2002). In some municipal drinking water wells in Sweden, measured concentrations of PFAS found to be several hundred times higher than the allowed threshold values. This has created a huge public concern and has recently attracted much media attention in Sweden (e.g. Afzelius et al., 2014; Bergman et al., 2014; Lewis et al., 2014). PFAS findings raised questions such as “What can we do to solve the problem?” When it comes to drinking water, there are a number of techniques that can ensure that PFAS levels are reduced to acceptable levels. This may be a costly challenge, but from a technical point of view it is possible. To ensure the safety of drinking water from a public health perspective is obviously a top priority. However, international experience shows that the cost of cleaning up PFAS in groundwater may be significantly higher than continuously treat drinking water in water works. Approximately fifty percent of Sweden’s drinking water comes from groundwater. As a result, there are several ongoing and planned PFAS-related environmental and drinking-water investigations in Sweden. Many aquifers that supply municipal water plants are located in areas of sand and gravel deposits. Such soils have relatively high permeabilities, which permits extraction of large volumes of water. However, the downside to high permeabilities is that they also allow dissolved contaminants as PFAS to spread over large areas. If one disregards the health risks linked to its presence in drinking water, PFAS have an impact on three of Sweden’s national environmental quality objectives, namely, A Non-Toxic Environment, Flourishing Lakes and Streams and Good-Quality Groundwater. Although the survey of PFAS in our groundwater supplies will take time, it is feasible. Much research in the field of hydrogeology and geochemistry remains before a viable and cost-effective groundwater remediation method can be operational. Until then, it is essential that measures are taken to identify the present distribution and magnitude of PFAS in groundwater and prevents its further spread in our most important aquifers. Afzelius, H. et al., 2014. Vågar vi dricka kranvattnet? (Do we dare drinking tap water?), Svenska Dagbladet. Bergman, Å., Hansson, S.O., Hellsten, E., 2014. En miljöskandal av historiska mått (An environmental scandal of historic proportions), Svenska Dagbladet. Lewis, J. et al., 2014. Kartlägg det förorenade dricksvattnet (Survey the contaminated drinking water), Svenska Dagbladet. OECD, 2002. Hazard Assessment of Perfluorooctane Sulfonate (PFOS) and its Salt.
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| 4. |
- Artursson, Tom, et al.
(författare)
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Drift correction for gas sensors using multivariate methods
- 2000
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Ingår i: Journal of Chemometrics. - 0886-9383 .- 1099-128X. ; 14:5-6, s. 711-723
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Tidskriftsartikel (refereegranskat)abstract
- Drift is one of the most serious impairments afflicting gas sensors. It can be seen as a gradual change in the sensor response over a long period of time when the external conditions an constant. This paper presents a new simple drift counteraction method based on PCA and PLS. The basic idea is to remove the drift direction component from the measurements. The direction of the drift, p, is calculated from measurements for a reference gas. Projecting the sample gas measurements on this vector gives the score vector t. The drift component tp(T) can then he removed from the sample gas data, which we call component correction (CC). The method is tested on a data set based on a reduced factorial design with four gases and a concentration gradient of hydrogen. It is found that the method works efficiently for both cases. Copyright (C) 2000 John Wiley & Sons, Ltd.
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| 5. |
- Dima, Elijs, et al.
(författare)
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LIFE: A Flexible Testbed For Light Field Evaluation
- 2018
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Konferensbidrag (refereegranskat)abstract
- Recording and imaging the 3D world has led to the use of light fields. Capturing, distributing and presenting light field data is challenging, and requires an evaluation platform. We define a framework for real-time processing, and present the design and implementation of a light field evaluation system. In order to serve as a testbed, the system is designed to be flexible, scalable, and able to model various end-to-end light field systems. This flexibility is achieved by encapsulating processes and devices in discrete framework systems. The modular capture system supports multiple camera types, general-purpose data processing, and streaming to network interfaces. The cloud system allows for parallel transcoding and distribution of streams. The presentation system encapsulates rendering and display specifics. The real-time ability was tested in a latency measurement; the capture and presentation systems process and stream frames within a 40 ms limit.
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| 6. |
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| 7. |
- Eriksson, Mikael, et al.
(författare)
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The MAX IV Facility
- 2013
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Ingår i: 11th International Conference on Synchrotron Radiation Instrumentation (SRI 2012). - : IOP Publishing. - 1742-6588 .- 1742-6596. ; 425
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Konferensbidrag (refereegranskat)abstract
- The MAX IV synchrotron radiation facility is currently being constructed in Lund, Sweden. The accelerator park consists of a 3 GeV linac injector and 2 storage rings operated at 1.5 and 3 GeV respectively. The linac injector will also be used for the generation of short Xray pulses. Close to 30 straight sections will be available for IDs at the rings. The three machines mentioned above are described below with some emphasis on the effort to create a very small emittance in the 3 GeV ring. Some unconventional technical solutions imposed by the emittance minimisation are discussed.
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| 8. |
- Eriksson, Mikael, et al.
(författare)
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The MAX IV Synchrotron Light Source
- 2011
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Ingår i: [Host publication title missing]. - 9789290833666 ; , s. 3026-3028
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Konferensbidrag (refereegranskat)abstract
- The MAX IV synchrotron radiation facility is currently being constructed in Lund, Sweden. It consists of a 3 GeV linac injector and 2 storage rings operated at 1.5 and 3 GeV respectively. The linac injector will also be used for the generation of short X-ray pulses. The three machines mentioned above are described with some emphasis on the effort to create a very small emittance in the 3 GeV ring. Some unconventional technical solutions will also be presented.
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| 9. |
- Leemann, Simon, et al.
(författare)
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Status of the MAX IV Storage Rings
- 2010
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Ingår i: Proceedings of IPAC’10. - 9789290833529 ; , s. 2618-2620
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Konferensbidrag (refereegranskat)abstract
- In 2009 the MAX IV facility was granted funding by Swedish authorities. Construction of the facility will begin this summer and user operation is expected by 2015. MAX IV will consist of a 3.4 GeV linac as a driver for a short-pulse radiation facility (with planned upgrade to a seeded/cascaded FEL) as well as an injector for two storage rings at different energies serving user communities in separate spectral ranges. Thanks to a novel compact multibend-achromat design, the 3 GeV ring will deliver a 500 mA electron beam with a horizontal emittance below 0.3 nmrad to x-ray insertion devices located in 19 dispersion-free 5 m straight sections. When the 3 GeV ring goes into operation in 2015 it is expected to become the highest electron-brightness storage ring light source world-wide. The 1.5 GeV ring will serve as a replacement for both present-day MAX II and MAX III storage rings. Its below 6 nm rad horizontal emittance electron beam will be delivered to IR and UV insertion devices in twelve 3.5 m straight sections. We report on design progress for the two new storage rings of the MAX IV facility.
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| 10. |
- Sjöström, Magnus, et al.
(författare)
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Orbit Feedback System for the MAX IV 3 GeV Storage Ring
- 2011
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Ingår i: [Host publication title missing]. - 9789290833666 ; , s. 499-501
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Konferensbidrag (refereegranskat)abstract
- The paper gives an overview of the planned orbit correc- tion system for the 3 GeV storage ring at the MAX IV lab- oratory, a light source facility currently under construction in Lund, Sweden[1, 2]. The ring will have a vertical beam size in the 1-4μm range in the insertion device (ID) straight sections depending on coupling[3], which places high re- quirements on the orbit stability. To meet this the ring will be equipped with 200 beam position monitors (BPMs) and two different sets of corrector magnets, which will be used by two separate orbit feedback loops; a slow orbit feedback (SOFB) loop to handle misalignments and drifts and a fast orbit feedback (FOFB) loop to reduce beam jitter. The pa- per also includes a brief description of the various engi- neering boundary conditions on the orbit feedback design for the MAX IV 3 GeV storage ring.
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