| 1. |
- Abelev, Betty, et al.
(författare)
-
Long-range angular correlations on the near and away side in p-Pb collisions at root S-NN=5.02 TeV
- 2013
-
Ingår i: Physics Letters. Section B: Nuclear, Elementary Particle and High-Energy Physics. - : Elsevier BV. - 0370-2693. ; 719:1-3, s. 29-41
-
Tidskriftsartikel (refereegranskat)abstract
- Angular correlations between charged trigger and associated particles are measured by the ALICE detector in p-Pb collisions at a nucleon-nucleon centre-of-mass energy of 5.02 TeV for transverse momentum ranges within 0.5 < P-T,P-assoc < P-T,P-trig < 4 GeV/c. The correlations are measured over two units of pseudorapidity and full azimuthal angle in different intervals of event multiplicity, and expressed as associated yield per trigger particle. Two long-range ridge-like structures, one on the near side and one on the away side, are observed when the per-trigger yield obtained in low-multiplicity events is subtracted from the one in high-multiplicity events. The excess on the near-side is qualitatively similar to that recently reported by the CMS Collaboration, while the excess on the away-side is reported for the first time. The two-ridge structure projected onto azimuthal angle is quantified with the second and third Fourier coefficients as well as by near-side and away-side yields and widths. The yields on the near side and on the away side are equal within the uncertainties for all studied event multiplicity and p(T) bins, and the widths show no significant evolution with event multiplicity or p(T). These findings suggest that the near-side ridge is accompanied by an essentially identical away-side ridge. (c) 2013 CERN. Published by Elsevier B.V. All rights reserved.
|
|
| 2. |
- Abelev, Betty, et al.
(författare)
-
Measurement of prompt J/psi and beauty hadron production cross sections at mid-rapidity in pp collisions at root s=7 TeV
- 2012
-
Ingår i: Journal of High Energy Physics. - 1029-8479. ; :11
-
Tidskriftsartikel (refereegranskat)abstract
- The ALICE experiment at the LHC has studied J/psi production at mid-rapidity in pp collisions at root s = 7 TeV through its electron pair decay on a data sample corresponding to an integrated luminosity L-int = 5.6 nb(-1). The fraction of J/psi from the decay of long-lived beauty hadrons was determined for J/psi candidates with transverse momentum p(t) > 1,3 GeV/c and rapidity vertical bar y vertical bar < 0.9. The cross section for prompt J/psi mesons, i.e. directly produced J/psi and prompt decays of heavier charmonium states such as the psi(2S) and chi(c) resonances, is sigma(prompt J/psi) (p(t) > 1.3 GeV/c, vertical bar y vertical bar < 0.9) = 8.3 +/- 0.8(stat.) +/- 1.1 (syst.)(-1.4)(+1.5) (syst. pol.) mu b. The cross section for the production of b-hadrons decaying to J/psi with p(t) > 1.3 GeV/c and vertical bar y vertical bar < 0.9 is a sigma(J/psi <- hB) (p(t) > 1.3 GeV/c, vertical bar y vertical bar < 0.9) = 1.46 +/- 0.38 (stat.)(-0.32)(+0.26) (syst.) mu b. The results are compared to QCD model predictions. The shape of the p(t) and y distributions of b-quarks predicted by perturbative QCD model calculations are used to extrapolate the measured cross section to derive the b (b) over bar pair total cross section and d sigma/dy at mid-rapidity.
|
|
| 3. |
- Abelev, Betty, et al.
(författare)
-
Underlying Event measurements in pp collisions at root s=0.9 and 7 TeV with the ALICE experiment at the LHC
- 2012
-
Ingår i: Journal of High Energy Physics. - 1029-8479. ; :7
-
Tidskriftsartikel (refereegranskat)abstract
- We present measurements of Underlying Event observables in pp collisions at root s = 0 : 9 and 7 TeV. The analysis is performed as a function of the highest charged-particle transverse momentum p(T),L-T in the event. Different regions are defined with respect to the azimuthal direction of the leading (highest transverse momentum) track: Toward, Transverse and Away. The Toward and Away regions collect the fragmentation products of the hardest partonic interaction. The Transverse region is expected to be most sensitive to the Underlying Event activity. The study is performed with charged particles above three different p(T) thresholds: 0.15, 0.5 and 1.0 GeV/c. In the Transverse region we observe an increase in the multiplicity of a factor 2-3 between the lower and higher collision energies, depending on the track p(T) threshold considered. Data are compared to PYTHIA 6.4, PYTHIA 8.1 and PHOJET. On average, all models considered underestimate the multiplicity and summed p(T) in the Transverse region by about 10-30%.
|
|
| 4. |
- Ardo, Shane, et al.
(författare)
-
Pathways to electrochemical solar-hydrogen technologies
- 2018
-
Ingår i: Energy & Environmental Science. - : Royal Society of Chemistry. - 1754-5692 .- 1754-5706. ; 11:10, s. 2768-2783
-
Forskningsöversikt (refereegranskat)abstract
- Solar-powered electrochemical production of hydrogen through water electrolysis is an active and important research endeavor. However, technologies and roadmaps for implementation of this process do not exist. In this perspective paper, we describe potential pathways for solar-hydrogen technologies into the marketplace in the form of photoelectrochemical or photovoltaic-driven electrolysis devices and systems. We detail technical approaches for device and system architectures, economic drivers, societal perceptions, political impacts, technological challenges, and research opportunities. Implementation scenarios are broken down into short-term and long-term markets, and a specific technology roadmap is defined. In the short term, the only plausible economical option will be photovoltaic-driven electrolysis systems for niche applications. In the long term, electrochemical solar-hydrogen technologies could be deployed more broadly in energy markets but will require advances in the technology, significant cost reductions, and/ or policy changes. Ultimately, a transition to a society that significantly relies on solar-hydrogen technologies will benefit from continued creativity and influence from the scientific community.
|
|
| 5. |
- Cuni-Sanchez, Aida, et al.
(författare)
-
High aboveground carbon stock of African tropical montane forests
- 2021
-
Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 596:7873, s. 536-542
-
Tidskriftsartikel (refereegranskat)abstract
- Tropical forests store 40–50 per cent of terrestrial vegetation carbon. However, spatial variations in aboveground live tree biomass carbon (AGC) stocks remain poorly understood, in particular in tropical montane forests. Owing to climatic and soil changes with increasing elevation, AGC stocks are lower in tropical montane forests compared with lowland forests. Here we assemble and analyse a dataset of structurally intact old-growth forests (AfriMont) spanning 44 montane sites in 12 African countries. We find that montane sites in the AfriMont plot network have a mean AGC stock of 149.4 megagrams of carbon per hectare (95% confidence interval 137.1–164.2), which is comparable to lowland forests in the African Tropical Rainforest Observation Network4 and about 70 per cent and 32 per cent higher than averages from plot networks in montane and lowland forests in the Neotropics, respectively. Notably, our results are two-thirds higher than the Intergovernmental Panel on Climate Change default values for these forests in Africa8. We find that the low stem density and high abundance of large trees of African lowland forests is mirrored in the montane forests sampled. This carbon store is endangered: we estimate that 0.8 million hectares of old-growth African montane forest have been lost since 2000. We provide country-specific montane forest AGC stock estimates modelled from our plot network to help to guide forest conservation and reforestation interventions. Our findings highlight the need for conserving these biodiverse and carbon-rich ecosystems.
|
|
| 6. |
- Jones, Geraint H., et al.
(författare)
-
The Comet Interceptor Mission
- 2024
-
Ingår i: Space Science Reviews. - : Springer Nature. - 0038-6308 .- 1572-9672. ; 220:1
-
Tidskriftsartikel (refereegranskat)abstract
- Here we describe the novel, multi-point Comet Interceptor mission. It is dedicated to the exploration of a little-processed long-period comet, possibly entering the inner Solar System for the first time, or to encounter an interstellar object originating at another star. The objectives of the mission are to address the following questions: What are the surface composition, shape, morphology, and structure of the target object? What is the composition of the gas and dust in the coma, its connection to the nucleus, and the nature of its interaction with the solar wind? The mission was proposed to the European Space Agency in 2018, and formally adopted by the agency in June 2022, for launch in 2029 together with the Ariel mission. Comet Interceptor will take advantage of the opportunity presented by ESA’s F-Class call for fast, flexible, low-cost missions to which it was proposed. The call required a launch to a halo orbit around the Sun-Earth L2 point. The mission can take advantage of this placement to wait for the discovery of a suitable comet reachable with its minimum Δ V capability of 600 ms − 1 . Comet Interceptor will be unique in encountering and studying, at a nominal closest approach distance of 1000 km, a comet that represents a near-pristine sample of material from the formation of the Solar System. It will also add a capability that no previous cometary mission has had, which is to deploy two sub-probes – B1, provided by the Japanese space agency, JAXA, and B2 – that will follow different trajectories through the coma. While the main probe passes at a nominal 1000 km distance, probes B1 and B2 will follow different chords through the coma at distances of 850 km and 400 km, respectively. The result will be unique, simultaneous, spatially resolved information of the 3-dimensional properties of the target comet and its interaction with the space environment. We present the mission’s science background leading to these objectives, as well as an overview of the scientific instruments, mission design, and schedule.
|
|
| 7. |
|
|
| 8. |
|
|
| 9. |
- Müller, Alexandra
(författare)
-
An evaluation of sources contributing to urban runoff pollution
- 2022
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Urban runoff is a significant pathway for the transport of diverse substances from the urban environment to receiving water bodies. Many of these substances are pollutants of environmental concern with potentially harmful effects on aquatic life. Detailed knowledge of the sources of pollutants entering stormwater runoff is needed to mitigate these effects.The overall aim of this doctoral thesis is therefore to provide new knowledge on the sources contributing to urban runoff pollution and to evaluate the specific contributions of micropollutants from two known major sources: building and structure surface materials, and vehicular activities. The work presented herein also (i) identifies pollutants that are expected to occur in runoff from buildings and other structure surfaces in the urban environment as well as in runoff from the road environment, (ii) estimates the concentrations of these pollutants released into runoff, and (iii) evaluates methods for identifying sources contributing to the pollution of urban stormwater runoff.The novel work presented in the thesis includes a critical review of the literature on sources contributing to urban runoff pollution, laboratory leaching tests and open-air sampling of pilot panels of building and structure surface materials, and field sampling of urban roadside snow. The literature review was not restricted in terms of type of pollution, while the experiments focused on selected metals and organic micropollutants including phthalates, alkylphenols, bisphenol A, and polycyclic aromatic hydrocarbons (PAHs).According to the literature review, atmospheric deposition, vehicular activities, and metallic building envelopes are the major pollution sources in the urban environment and have been studied far more extensively than other sources. Moreover, their dominance is likely to continue given their central roles in urban environments. The experimental results confirmed that vehicular activities were sources of octylphenols, bisphenol A, and phthalates as well as the metal(loid)s Sb and W, both of which were rarely determined in previous studies on urban runoff. Building and structure surface materials such as copper sheets, zinc sheets, and polyvinyl chloride (PVC) roofing membranes were found to release Cu, Zn, nonylphenols, and phthalates. Among alkylphenols, nonylphenols were predominantly found in building surface runoff while octylphenols occurred predominantly in roadside snow. Metals occurred more commonly in dissolved (<0.45 μm) form in building surface runoff than in roadside snow, where metals were mainly attached to particles.A comparison of methods for identifying building surface materials contributing to runoff pollution showed that laboratory leaching tests were generally effective for source identification but not for estimating concentrations in actual runoff, whereas open-air pilot studies were resource-intensive but give results that agree well with analyses of real runoff. In addition, the release of pollutants from building surface materials subjected to in-situ ageing was investigated and the water quality of rainwater-induced runoff was compared to that of snowmelt-induced runoff; neither of these issues were adequately addressed in the previous literature. These studies showed that pollutant concentrations were generally higher in rain runoff than in snowmelt runoff and that pollutant releases from most materials and substances exhibited no decreasing or increasing trend over time. However, the release of nonylphenols from one of the PVCs did decrease over time, possibly because of washing out and material ageing.
|
|
| 10. |
- Müller, Alexandra, et al.
(författare)
-
Building surface materials as sources of micropollutants in building runoff : A pilot study
- 2019
-
Ingår i: Science of the Total Environment. - : Elsevier. - 0048-9697 .- 1879-1026. ; 680, s. 190-197
-
Tidskriftsartikel (refereegranskat)abstract
- Control of diffuse pollution is critical for achieving good surface water quality status. In this context, pollutant contributions from building materials have received increased attention in recent decades. This study examined the releases of metals, nonylphenols and phthalates from ten common building surface materials (installed in triplicates) into rainwater runoff from six rain events. The highest releases of metals were from copper and zinc sheets (average concentrations of 3090 μg/L Cu and 7770 μg/L Zn respectively), while other metal materials, e.g., Corten weathering steel, exhibited lower releases. PVC roofing released high concentrations of nonylphenols and phthalates (average concentrations of up to 26 μg/L nonylphenols and 455 μg/L Diisononyl phthalate, DINP) which have not been investigated in the earlier studies. Pollutant releases varied between events, likely because of weather conditions and rainfall characteristics. Study findings should be valuable for environmentally responsible applications of the existing building materials and the development of new ones, as well as the investigations and risk assessment of specific pollutants in stormwater.
|
|
