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- Aamodt, K., et al.
(författare)
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The ALICE experiment at the CERN LHC
- 2008
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Ingår i: Journal of Instrumentation. - 1748-0221. ; 3:S08002
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Forskningsöversikt (refereegranskat)abstract
- ALICE (A Large Ion Collider Experiment) is a general-purpose, heavy-ion detector at the CERN LHC which focuses on QCD, the strong-interaction sector of the Standard Model. It is designed to address the physics of strongly interacting matter and the quark-gluon plasma at extreme values of energy density and temperature in nucleus-nucleus collisions. Besides running with Pb ions, the physics programme includes collisions with lighter ions, lower energy running and dedicated proton-nucleus runs. ALICE will also take data with proton beams at the top LHC energy to collect reference data for the heavy-ion programme and to address several QCD topics for which ALICE is complementary to the other LHC detectors. The ALICE detector has been built by a collaboration including currently over 1000 physicists and engineers from 105 Institutes in 30 countries, Its overall dimensions are 16 x 16 x 26 m(3) with a total weight of approximately 10 000 t. The experiment consists of 18 different detector systems each with its own specific technology choice and design constraints, driven both by the physics requirements and the experimental conditions expected at LHC. The most stringent design constraint is to cope with the extreme particle multiplicity anticipated in central Pb-Pb collisions. The different subsystems were optimized to provide high-momentum resolution as well as excellent Particle Identification (PID) over a broad range in momentum, up to the highest multiplicities predicted for LHC. This will allow for comprehensive studies of hadrons, electrons, muons, and photons produced in the collision of heavy nuclei. Most detector systems are scheduled to be installed and ready for data taking by mid-2008 when the LHC is scheduled to start operation, with the exception of parts of the Photon Spectrometer (PHOS), Transition Radiation Detector (TRD) and Electro Magnetic Calorimeter (EMCal). These detectors will be completed for the high-luminosity ion run expected in 2010. This paper describes in detail the detector components as installed for the first data taking in the summer of 2008.
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- Zaborowski, AM, et al.
(författare)
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Microsatellite instability in young patients with rectal cancer: molecular findings and treatment response
- 2022
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Ingår i: The British journal of surgery. - : Oxford University Press (OUP). - 1365-2168 .- 0007-1323. ; 109:3, s. 251-255
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Tidskriftsartikel (refereegranskat)abstract
- In this study of 400 patients with early-onset rectal cancer, 12.5 per cent demonstrated microsatellite instability (MSI). MSI was associated with a reduced likelihood of nodal positivity, an increased rate of pathological complete response, and improved disease-specific survival.
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- Alme, J., et al.
(författare)
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The ALICE TPC, a large 3-dimensional tracking device with fast readout for ultra-high multiplicity events
- 2010
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Ingår i: Nuclear Instruments & Methods in Physics Research. Section A: Accelerators, Spectrometers, Detectors, and Associated Equipment. - : Elsevier BV. - 0167-5087 .- 0168-9002. ; 622:1, s. 316-367
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Tidskriftsartikel (refereegranskat)abstract
- The design, construction, and commissioning of the ALICE Time-Projection Chamber (TPC) is described. It is the main device for pattern recognition, tracking, and identification of charged particles in the ALICE experiment at the CERN LHC. The TPC is cylindrical in shape with a volume close to 90 m(3) and is operated in a 0.5T solenoidal magnetic field parallel to its axis. In this paper we describe in detail the design considerations for this detector for operation in the extreme multiplicity environment of central Pb-Pb collisions at LHC energy. The implementation of the resulting requirements into hardware (field cage, read-out chambers, electronics), infrastructure (gas and cooling system, laser-calibration system), and software led to many technical innovations which are described along with a presentation of all the major components of the detector, as currently realized. We also report on the performance achieved after completion of the first round of stand-alone calibration runs and demonstrate results close to those specified in the TPC Technical Design Report. (C) 2010 CERN for the benefit of the ALICE collaboration. Published by Elsevier B.V. All rights reserved.
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- Cortes, Andres J., et al.
(författare)
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Small-scale patterns in snowmelt timing affect gene flow and the distribution of genetic diversity in the alpine dwarf shrub Salix herbacea
- 2014
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Ingår i: Heredity. - : Springer Science and Business Media LLC. - 0018-067X .- 1365-2540. ; 113:3, s. 233-239
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Tidskriftsartikel (refereegranskat)abstract
- Current threats to biodiversity, such as climate change, are thought to alter the within-species genetic diversity among microhabitats in highly heterogeneous alpine environments. Assessing the spatial organization and dynamics of genetic diversity within species can help to predict the responses of organisms to environmental change. In this study, we evaluated whether small-scale heterogeneity in snowmelt timing restricts gene flow between microhabitats in the common long-lived dwarf shrub Salix herbacea L. We surveyed 273 genets across 12 early-and late-snowmelt sites (that is, ridges and snowbeds) in the Swiss Alps for phenological variation over 2 years and for genetic variation using seven SSR markers. Phenological differentiation triggered by differences in snowmelt timing did not correlate with genetic differentiation between microhabitats. On the contrary, extensive gene flow appeared to occur between microhabitats and slightly less extensively among adjacent mountains. However, ridges exhibited significantly lower levels of genetic diversity than snowbeds, and patterns of effective population size (Ne) and migration (Nem) between microhabitats were strongly asymmetric, with ridges acting as sources and snowbeds as sinks. As no recent genetic bottlenecks were detected in the studied sites, this asymmetry is likely to reflect current metapopulation dynamics of the species dominated by gene flow via seeds rather than ancient re-colonization after the last glacial period. Overall, our results suggest that seed dispersal prevents snowmelt-driven genetic isolation, and snowbeds act as sinks of genetic diversity. We discuss the consequences of such small-scale variation in gene flow and diversity levels for population responses to climate change.
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- Pustovalova, Y., et al.
(författare)
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NUScon: a community-driven platform for quantitative evaluation of nonuniform sampling in NMR
- 2021
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Ingår i: Magnetic Resonance. - : Copernicus GmbH. - 2699-0016. ; 2:2, s. 843-861
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Tidskriftsartikel (refereegranskat)abstract
- Although the concepts of nonuniform sampling (NUS) and non-Fourier spectral reconstruction in multidimensional NMR began to emerge 4 decades ago (Bodenhausen and Ernst, 1981; Barna and Laue, 1987), it is only relatively recently that NUS has become more commonplace. Advantages of NUS include the ability to tailor experiments to reduce data collection time and to improve spectral quality, whether through detection of closely spaced peaks (i.e., “resolution”) or peaks of weak intensity (i.e., “sensitivity”). Wider adoption of these methods is the result of improvements in computational performance, a growing abundance and flexibility of software, support from NMR spectrometer vendors, and the increased data sampling demands imposed by higher magnetic fields. However, the identification of best practices still remains a significant and unmet challenge. Unlike the discrete Fourier transform, non-Fourier methods used to reconstruct spectra from NUS data are nonlinear, depend on the complexity and nature of the signals, and lack quantitative or formal theory describing their performance. Seemingly subtle algorithmic differences may lead to significant variabilities in spectral qualities and artifacts. A community-based critical assessment of NUS challenge problems has been initiated, called the “Nonuniform Sampling Contest” (NUScon), with the objective of determining best practices for processing and analyzing NUS experiments. We address this objective by constructing challenges from NMR experiments that we inject with synthetic signals, and we process these challenges using workflows submitted by the community. In the initial rounds of NUScon our aim is to establish objective criteria for evaluating the quality of spectral reconstructions. We present here a software package for performing the quantitative analyses, and we present the results from the first two rounds of NUScon. We discuss the challenges that remain and present a roadmap for continued community-driven development with the ultimate aim of providing best practices in this rapidly evolving field. The NUScon software package and all data from evaluating the challenge problems are hosted on the NMRbox platform.
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| 9. |
- Wheeler, J. A., et al.
(författare)
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Increased spring freezing vulnerability for alpine shrubs under early snowmelt
- 2014
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Ingår i: Oecologia. - : Springer Science and Business Media LLC. - 0029-8549 .- 1432-1939. ; 175:1, s. 219-229
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Tidskriftsartikel (refereegranskat)abstract
- Alpine dwarf shrub communities are phenologically linked with snowmelt timing, so early spring exposure may increase risk of freezing damage during early development, and consequently reduce seasonal growth. We examined whether environmental factors (duration of snow cover, elevation) influenced size and the vulnerability of shrubs to spring freezing along elevational gradients and snow microhabitats by modelling the past frequency of spring freezing events. We sampled biomass and measured the size of Salix herbacea, Vaccinium myrtillus, Vaccinium uliginosum and Loiseleuria procumbens in late spring. Leaves were exposed to freezing temperatures to determine the temperature at which 50 % of specimens are killed for each species and sampling site. By linking site snowmelt and temperatures to long-term climate measurements, we extrapolated the frequency of spring freezing events at each elevation, snow microhabitat and per species over 37 years. Snowmelt timing was significantly driven by microhabitat effects, but was independent of elevation. Shrub growth was neither enhanced nor reduced by earlier snowmelt, but decreased with elevation. Freezing resistance was strongly species dependent, and did not differ along the elevation or snowmelt gradient. Microclimate extrapolation suggested that potentially lethal freezing events (in May and June) occurred for three of the four species examined. Freezing events never occurred on late snow beds, and increased in frequency with earlier snowmelt and higher elevation. Extrapolated freezing events showed a slight, non-significant increase over the 37-year record. We suggest that earlier snowmelt does not enhance growth in four dominant alpine shrubs, but increases the risk of lethal spring freezing exposure for less freezing-resistant species.
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| 10. |
- Wheeler, J. A., et al.
(författare)
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With a little help from my friends : community facilitation increases performance in the dwarf shrub Salix herbacea
- 2015
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Ingår i: Basic and Applied Ecology. - : Elsevier BV. - 1439-1791 .- 1618-0089. ; 16:3, s. 202-209
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Tidskriftsartikel (refereegranskat)abstract
- Shifts between positive and negative plant interactions along environmental stress gradients can affect alpine plant performance. We removed neighbours around Salix herbacea, a common arctic and alpine dwarf shrub, along elevational and snowmelt gradients on three mountains in Switzerland. The objectives of our study were to determine the effect of neighbours on phenological, morphological, and fitness traits ofS. herbacea, and to determine whether neighbour interactions shift from competition to facilitation along environmental stress gradients.Target plants without neighbours required less time for fruit production; however, they also were more likely to be damaged by caterpillar herbivory. Effects of neighbour removal changed along the environmental gradients: plants without neighbours had smaller leaves on earlier snowmelt sites, and increased fungal damage with increasing elevation. Without neighbour removal, damage generally led to reduced female flowering under later snowmelt conditions in the following summer.Our results indicate that the majority of neighbour interactions influencing S. herbacea are facilitative, particularly at stressful early snowmelt and high elevation sites. We suggest that neighbours moderate environmental conditions by protecting plants from temperature extremes, and reduce plant apparency to caterpillars. Neighbours also indirectly increase fitness by reducing damage. Facilitation by neighbours may become more important under climate change, as early snowmelt may increase stress.
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