| 1. |
- Accomando, E., et al.
(författare)
-
Physics with e + e - linear colliders
- 1998
-
Ingår i: Physics Reports. - 0370-1573. ; 299:1, s. 1-78
-
Tidskriftsartikel (refereegranskat)abstract
- The physics potential of e + e - linear colliders is summarized in this report. These machines are planned to operate in the first phase at a center-of-mass energy of 500 GeV, before being scaled up to about 1 TeV. In the second phase of the operation, a final energy of about 2 TeV is expected. The machines will allow us to perform precision tests of the heavy particles in the Standard Model, the top quark and the electroweak bosons. They are ideal facilities for exploring the properties of Higgs particles, in particular in the intermediate mass range. New vector bosons and novel matter particles in extended gauge theories can be searched for and studied thoroughly. The machines provide unique opportunities for the discovery of particles in supersymmetric extensions of the Standard Model, the spectrum of Higgs particles, the supersymmetric partners of the electroweak gauge and Higgs bosons, and of the matter particles. High precision analyses of their properties and interactions will allow for extrapolations to energy scales close to the Planck scale where gravity becomes significant. In alternative scenarios, i.e. compositeness models, novel matter particles and interactions can be discovered and investigated in the energy range above the existing colliders up to the TeV scale. Whatever scenario is realized in Nature, the discovery potential of e + e - linear colliders and the high precision with which the properties of particles and their interactions can be analyzed, define an exciting physics program complementary to hadron machines.
|
|
| 2. |
|
|
| 3. |
- Ammann, B, et al.
(författare)
-
The Würmian Late-glacial in lowland Switzerland
- 1994
-
Ingår i: Journal of Quaternary Science. - : Wiley. - 0267-8179 .- 1099-1417. ; 9:2, s. 119-125
-
Tidskriftsartikel (refereegranskat)abstract
- A synthesis is provided of Late-glacial (14-9 ka BP) environmental changes in lowland Switzerland (the 'Swiss Plateau'). The chronology of deglaciation and subsequent developments in vegetation cover in the area are summarised. The sequence of climatic variations experienced in the region during the Late-glacial is then described and a curve representing the main palaeotemperature variations is presented.
|
|
| 4. |
- Bigler, Christian, et al.
(författare)
-
Quantifying human-induced eutrophication in Swiss mountain lakes since AD 1800 using diatoms
- 2007
-
Ingår i: The Holocene. - : SAGE Publications. - 0959-6836 .- 1477-0911. ; 17:8, s. 1141-1154
-
Tidskriftsartikel (refereegranskat)abstract
- Sedimentary diatom assemblages from three lakes in the southeastern Swiss Alps were analysed at high temporal resolution since AD 1800. Altered land-use patterns, increasing population and exploitation through tourism are clearly reflected in annually laminated sediments of Lej da San Murezzan (Lake St Moritz) and Lej da Silvaplauna (Lake Silvaplana). Diatom assemblages originally dominated by Cyclotella taxa are replaced by taxa indicating higher total phosphorus (TP) concentrations, such as Asterionella formosa, Fragilaria crotonensis and Stephanodiscus parvus. In Lej da la Tscheppa, located well above the treeline in a catchment that was hardly exposed to human impact, Cyclotella comensis prevails throughout the entire sediment sequence. Quantitative estimates of past TP concentrations were inferred using a newly developed regional diatom-TP inference model based on 119 modern samples. In Lej da la Tscheppa diatoms imply stable, low TP concentrations (~10 µg/l), which can be considered as natural background concentration. Elevated TP levels are inferred for Lej da San Murezzan (max. 60 µg/l) since AD 1910 and for Lej da Silvaplauna (max. 40 µg/l) since AD 1950, corroborated by changes in sedimentary biogenic silica concentration and organic carbon content. Since ~AD 1970 improved waste water management led to a considerable reduction in TP loading in Lej da Silvaplauna and Lej da San Murezzan.
|
|
| 5. |
- van Hardenbroek, M., et al.
(författare)
-
Evidence for past variations in methane availability in a Siberian thermokarst lake based on delta C-13 of chitinous invertebrate remains
- 2013
-
Ingår i: Quaternary Science Reviews. - : Elsevier BV. - 0277-3791 .- 1873-457X. ; 66, s. 74-84
-
Tidskriftsartikel (refereegranskat)abstract
- Understanding past methane dynamics in arctic wetlands and lakes is crucial for estimating future methane release. Methane fluxes from lake ecosystems have increasingly been studied, yet only few reconstructions of past methane emissions from lakes are available. In this study, we develop an approach to assess changes in methane availability in lakes based on delta C-13 of chitinous invertebrate remains and apply this to a sediment record from a Siberian thermokarst lake. Diffusive methane fluxes from the surface of ten newly sampled Siberian lakes and seven previously studied Swedish lakes were compared to taxon-specific delta C-13 values of invertebrate remains from lake surface sediments to investigate whether these invertebrates assimilated C-13-depleted carbon typical for methane. Remains of chironomid larvae of the tribe Orthocladiinae that, in the study lakes, mainly assimilate plant-derived carbon had higher delta C-13 than other invertebrate groups. delta C-13 of other invertebrates such as several chironomid groups (Chironomus, Chironomini, Tanytarsini, and Tanypodinae), cladocerans (Daphnia), and ostracods were generally lower. delta C-13 of Chironomini and Daphnia, and to a lesser extent Tanytarsini was variable in the lakes and lower at sites with higher diffusive methane fluxes. delta C-13 of Chironomini, Tanytarsini, and Daphnia were correlated significantly with diffusive methane flux in the combined Siberian and Swedish dataset (r = -0.72, p = 0.001, r = -0.53, p = 0.03, and r = -0.81, p < 0.001, respectively), suggesting that delta C-13 in these invertebrates was affected by methane availability. In a second step, we measured delta C-13 of invertebrate remains from a sediment record of Lake S1, a shallow thermokarst lake in northeast Siberia. In this record, covering the past ca 1000 years, delta C-13 of taxa most sensitive to methane availability (Chironomini, Tanytarsini, and Daphnia) was lowest in sediments deposited from ca AD 1250 to ca AD 1500, and after AD 1970, coinciding with warmer climate as indicated by an independent local temperature record. As a consequence the offset in delta C-13 between methane-sensitive taxa and bulk organic matter was higher in these sections than in other parts of the core. In contrast, delta C-13 of other invertebrate taxa did not show this trend. Our results suggest higher methane availability in the study lake during warmer periods and that thermokarst lakes can respond dynamically in their methane output to changing environmental conditions. (C) 2012 Elsevier Ltd. All rights reserved.
|
|
| 6. |
- Ammann, B, et al.
(författare)
-
Switzerland
- 1996
-
Annan publikation (övrigt vetenskapligt/konstnärligt)
|
|
| 7. |
|
|
| 8. |
|
|
| 9. |
- van Hardenbroek, M, et al.
(författare)
-
Relationship between d13C of chironomid remains and methane flux in Swedish lakes
- 2012
-
Ingår i: Freshwater Biology. - : Blackwell Publishing. - 0046-5070 .- 1365-2427. ; 57:1, s. 166-177
-
Tidskriftsartikel (refereegranskat)abstract
- 1. Methanogenic carbon can be incorporated by methane-oxidising bacteria, leading to a 13C-depleted stable carbon isotopic composition (d13C) of chironomids that feed on these microorganisms. This has been shown for the chironomid tribe Chironomini, but very little information is available about the d13C of other abundant chironomid groups and the relationship between chironomid d13C and methane production in lakes.
|
|
| 10. |
- van Hardenbroek, M., et al.
(författare)
-
Taxon-specific δ13C analysis of chitinous invertebrate remains in sediments from Strandsjön, Sweden
- 2014
-
Ingår i: Journal of Paleolimnology. - : Springer Netherlands. - 0921-2728 .- 1573-0417. ; 52:1-2, s. 95-105
-
Tidskriftsartikel (refereegranskat)abstract
- Taxon-specific stable carbon isotope (delta C-13) analysis of chitinous remains of invertebrates can provide valuable information about the carbon sources used by invertebrates living in specific habitats of lake ecosystems (for example, sediments, water column, or aquatic vegetation). This is complementary to delta C-13 of sedimentary organic matter (SOM), which provides an integrated signal of organic matter produced in a lake and its catchment, and of diagenetic processes within sediments. In a sediment record from Strandsjon (Sweden) covering the past circa 140 years, we analyzed SOM geochemistry (delta C-13, C:N-atomic, organic carbon content) and delta C-13 of chitinous invertebrate remains in order to examine whether taxon-specific delta C-13 records could be developed for different invertebrate groups and whether these analyses provide insights into past changes of organic carbon sources for lacustrine invertebrates available in benthic and planktonic compartments of the lake. Invertebrate taxa included benthic chironomids (Chironomus, Chironomini excluding Chironomus, Tanytarsini, and Tanypodinae), filter-feeders on suspended particulate organic matter (Daphnia, Plumatella and Cristatella mucedo), and Rhabdocoela. delta C-13 of chironomid remains indicated periodic availability of C-13-depleted carbon sources in the benthic environment of the lake as delta C-13 values of the different chironomid taxa fluctuated simultaneously between -34.7 and -30.5 aEuro degrees (VPDB). Daphnia and Bryozoa showed parallel changes in their delta C-13 values which did not coincide with variations in delta C-13 of chironomids, though, and a 2-3 aEuro degrees decrease since circa AD 1960. The decrease in delta C-13 of Daphnia and Bryozoa could indicate a decrease in phytoplankton delta C-13 as a result of lower lake productivity, which is in accordance with historical information about the lake that suggests a shift to less eutrophic conditions after AD 1960. In contrast, Rhabdocoela cocoons were characterized by relatively high delta C-13 values (-30.4 to -28.2 aEuro degrees) that did not show a strong temporal trend, which could be related to the predatory feeding mode and wide prey spectrum of this organism group. The taxon-specific delta C-13 analyses of invertebrate remains indicated that different carbon sources were available for the benthic chironomid larvae than for the filter-feeding Daphnia and bryozoans. Our results therefore demonstrate that taxon-specific analysis of delta C-13 of organic invertebrate remains can provide complementary information to measurements on bulk SOM and that delta C-13 of invertebrate remains may allow the reconstruction of past changes in carbon sources and their delta C-13 in different habitats of lake ecosystems.
|
|
| 11. |
- von Gunten, L., et al.
(författare)
-
Seasonal temperatures for the past ~400 years reconstructed from diatom and chironomid assemblages in a high-altitude lake (Lej da la Tscheppa, Switzerland)
- 2008
-
Ingår i: Journal of Paleolimnology. - : Springer Science and Business Media LLC. - 0921-2728 .- 1573-0417. ; 39, s. 283–299-
-
Tidskriftsartikel (refereegranskat)abstract
- We analysed a 42 cm long sediment record from Lej da la Tscheppa, a high-altitude lake (2,616 m a.s.l.) in the Upper Engadine valley (Switzerland) for subfossil diatoms, chironomids and pollen. The chronology of the top 21 cm of the record was established using 210Pb analysis using a constant-rate-of-supply model, and validated with 137Cs measurements and the content of spheroidal carbonaceous particles. A tentative chronology for the lower part of the core was obtained through extrapolation of the sedimentation rates in the uppermost part of the record. Pollen assemblages in the record reflect regional changes in forestation and land-use patterns in the Upper Engadine valley and show no evidenceof significant local human activity in the lake’s catchment. Diatom assemblages record a distinct increase in planktonic taxa since the early 19th century, suggesting a decrease in the duration of ice-cover. In contrast, chironomid assemblages remained stable during a large part of the record. We applied an established chironomid-based July air temperature transfer function and a newly developed diatom-based spring air temperature transfer function to reconstruct past seasonal air temperature changes at Lej da la Tscheppa. The reconstructions indicate a diatom-inferred warming trend in spring temperatures during the past ca. 400 years, whereas chironomid-inferred summer temperatures suggest a slight cooling trend.
|
|
