| 1. |
- Abt, I, et al.
(författare)
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Inclusive V-0 production cross sections from 920 GeV fixed target proton-nucleus collisions
- 2003
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Ingår i: European Physical Journal C. Particles and Fields. - : Springer Science and Business Media LLC. - 1434-6044. ; 29:2, s. 181-190
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Tidskriftsartikel (refereegranskat)abstract
- Inclusive differential cross sections dsigma(pA)/dx(F) and dsigma(pA)/dp(t)(2) for the production of K-S(0), Lambda, and (&ULambda;) over bar particles are measured at HERA in proton-induced reactions on C, Al, Ti, and W targets. The incident beam energy is 920 GeV, corresponding to roots = 41.6 GeV in the proton-nucleon system. The ratios of differential cross sections dsigma(pA)(K-S(0))/dsigma(pA)(Lambda) and dsigma(pA)((&ULambda;) over bar)/dsigma(pA) (Lambda) are measured to be 6.2 +/- 0.5 and 0.66 +/- 0.07, respectively, for x(F) approximate to -0.06. No significant dependence upon the target material is observed. Within errors, the slopes of the transverse momentum distributions da,Ald t also show no significant dependence upon the target material. The dependence of the extrapolated total cross sections sigma(pA) on the atomic mass A of the target material is discussed, and the deduced cross sections per nucleon sigma(pN) are compared with results obtained at other energies.
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| 2. |
- Abt, I, et al.
(författare)
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Measurement of the b(b)over-bar production cross section in 920 GeV fixed-target proton-nucleus collisions
- 2003
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Ingår i: European Physical Journal C. Particles and Fields. - : Springer Science and Business Media LLC. - 1434-6044. ; 26:3, s. 345-355
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Tidskriftsartikel (refereegranskat)abstract
- Using the HERA-B detector, the b (b) over bar production cross section has been measured in 920 GeV proton collisions on carbon and titanium targets. The b (b) over bar production was tagged via inclusive bottom quark decays into J/psi by exploiting the longitudinal separation of J/psi --> l(+)l(-) decay vertices from the primary proton-nucleus interaction. Both e(+)e(-) and mu(+)mu(-) channels have been reconstructed and the combined analysis yields the cross section sigma(b (b) over bar) = 32(-12)(+14)(stat) (+6)(-7)(sys) nb/nucleon.
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| 3. |
- Faatz, B., et al.
(författare)
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Simultaneous operation of two soft x-ray free-electron lasers driven by one linear accelerator
- 2016
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Ingår i: New Journal of Physics. - : IOP Publishing. - 1367-2630. ; 18
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Tidskriftsartikel (refereegranskat)abstract
- Extreme-ultraviolet to x-ray free-electron lasers (FELs) in operation for scientific applications are up to now single-user facilities. While most FELs generate around 100 photon pulses per second, FLASH at DESY can deliver almost two orders of magnitude more pulses in this time span due to its superconducting accelerator technology. This makes the facility a prime candidate to realize the next step in FELs-dividing the electron pulse trains into several FEL lines and delivering photon pulses to several users at the same time. Hence, FLASH has been extended with a second undulator line and self-amplified spontaneous emission (SASE) is demonstrated in both FELs simultaneously. FLASH can now deliver MHz pulse trains to two user experiments in parallel with individually selected photon beam characteristics. First results of the capabilities of this extension are shown with emphasis on independent variation of wavelength, repetition rate, and photon pulse length.
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| 4. |
- Allison, J, et al.
(författare)
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Geant4 developments and applications
- 2006
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Ingår i: IEEE TRANSACTIONS ON NUCLEAR SCIENCE. - 0018-9499. ; 53:1, s. 270-278
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
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| 5. |
- Li, Jian-Yang, et al.
(författare)
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Ejecta from the DART-produced active asteroid Dimorphos
- 2023
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Ingår i: Nature. - : Springer Nature. - 0028-0836 .- 1476-4687. ; 616, s. 452-456
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Tidskriftsartikel (refereegranskat)abstract
- Some active asteroids have been proposed to be formed as a result of impact events1. Because active asteroids are generally discovered by chance only after their tails have fully formed, the process of how impact ejecta evolve into a tail has, to our knowledge, not been directly observed. The Double Asteroid Redirection Test (DART) mission of NASA2, in addition to having successfully changed the orbital period of Dimorphos3, demonstrated the activation process of an asteroid resulting from an impact under precisely known conditions. Here we report the observations of the DART impact ejecta with the Hubble Space Telescope from impact time T + 15 min to T + 18.5 days at spatial resolutions of around 2.1 km per pixel. Our observations reveal the complex evolution of the ejecta, which are first dominated by the gravitational interaction between the Didymos binary system and the ejected dust and subsequently by solar radiation pressure. The lowest-speed ejecta dispersed through a sustained tail that had a consistent morphology with previously observed asteroid tails thought to be produced by an impact4,5. The evolution of the ejecta after the controlled impact experiment of DART thus provides a framework for understanding the fundamental mechanisms that act on asteroids disrupted by a natural impact1,6.
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| 6. |
- Dotti, N., et al.
(författare)
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Conduction mechanism of nitronyl-nitroxide molecular magnetic compounds
- 2016
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Ingår i: Physical Review B (Condensed Matter and Materials Physics). - 1098-0121. ; 93:16
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Tidskriftsartikel (refereegranskat)abstract
- We investigate the conduction mechanisms of nitronyl-nitroxide (NIT) molecular radicals, as useful for the creation of nanoscopic molecular spintronic devices, finding that it does not correspond to standard Mott behavior, as previously postulated. We provide a complete investigation using transport measurements, low-energy, sub-THz spectroscopy and introducing differently substituted phenyl appendages. We show that a nontrivial surface-charge-limited regime is present in addition to the standard low-voltage Ohmic conductance. Scaling analysis allows one to determine all the main transport parameters for the compounds and highlights the presence of charge-trapping effects. Comparison among the different compounds shows the relevance of intermolecular stacking between the aromatic ring of the phenyl appendix and the NIT motif in the creation of useful electron transport channels. The importance of intermolecular pathways is further highlighted by electronic structure calculations, which clarify the nature of the electronic channels and their effect on the Mott character of the compounds.
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| 7. |
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| 8. |
- Dressel, Sabrina, et al.
(författare)
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Evaluating the outcomes of collaborative wildlife governance : The role of social-ecological system context and collaboration dynamics
- 2020
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Ingår i: Land use policy. - : Elsevier. - 0264-8377 .- 1873-5754. ; 99
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Tidskriftsartikel (refereegranskat)abstract
- The acknowledgement of uncertainty and complexity in social-ecological systems has increased the implementation of collaborative governance regimes for environmental issues. The performance of these new regimes to deliver favourable social and ecological outcomes must therefore be evaluated. We focus on the case of Swedish wildlife governance, which has a tradition of using collaborative elements. In relation to moose (Alces alces), these collaborative aspects were recently formalized in an amended policy. We aim to assess some aspects of this new regime's performance with respect to intermediate ecological outcomes (i.e. quota fulfilment). We use path analysis to test the causal effects of system context and collaboration dynamics on governance outcomes. Collaboration dynamics were assessed using a web-based survey sent to all stakeholders in Moose Management Groups (response rate = 82 %). Our originally specified model yielded a good fit (SRMR of .030 and robust TLI of .996) and explained 20 % of the variation in outcomes. Context variables revealed significant direct effects on collaboration dynamics and outcomes. Larger Moose Management Areas and fluctuations in forage availability required more time investment from actors, while high land use diversity and density of other ungulate species negatively affected moose quota fulfilment. Moose Management Groups that invested more time and perceived to have a good knowledge base achieved better quota fulfilment. Collaboration dynamics thus had a positive direct effect on outcomes. From a policy perspective, our results raise questions regarding institutional fit because context factors had significant negative effects on collaboration dynamics and the outcomes of the collaborative process.
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| 9. |
- Gorshunov, B. P., et al.
(författare)
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Subterahertz electrodynamics of (TMTSF)(2)X (X = ClO4, PF6) salts
- 2013
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Ingår i: Journal of Experimental and Theoretical Physics. - 1063-7761 .- 1090-6509. ; 116:3, s. 460-466
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Tidskriftsartikel (refereegranskat)abstract
- The terahertz-subterahertz spectra of the complex permittivity and dynamic conductivity of polycrystalline (TMTSF)(2)ClO4 and (TMTSF)(2)PF6 samples are measured quantitatively. The spectra of (TMTSF)(2)ClO4 have absorption lines at frequencies of 7 and 30 cm(-1). The obtained temperature dependences of the line parameters in the range 5-300 K cast some doubt on the earlier concept of their phonon origin. An excitation is detected at temperatures below 20 K in the frequency range near 30 cm(-1), and its nature is related to the activation of a transverse acoustic phonon caused by the folding of the Brillouin zone due to the ordering of noncentrosymmetrical anions below 20 K. An increase in the carrier relaxation rate is found in this temperature range, which indicates a close relation between the electron and phonon subsystems in (TMTSF)(2)ClO4. Sings of additional low-energy excitations that should manifest themselves at frequencies below 1-2 cm(-1) are detected. (TMTSF)(2)PF6 containing centrosymmetrical anions has no absorption lines in the frequency range 3-20 cm(-1) and the temperature range 5-300 K.
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| 10. |
- Johansson, M., et al.
(författare)
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Expectations about voluntary efforts in collaborative governance and the fit with perceived prerequisites of intrinsic motivation in Sweden?s ecosystem-based moose management system
- 2022
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Ingår i: Ecology and Society. - : Resilience Alliance, Inc.. - 1708-3087. ; 27:2
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Tidskriftsartikel (refereegranskat)abstract
- Collaborative governance regimes may be vulnerable because of dependency on stakeholders??? voluntary engagement and efforts. This study focuses on the Swedish moose management system, a multi-level collaborative governance regime inspired by the ecosystem approach. Self-determination theory is used to explore perceived prerequisites of basic needs for intrinsic motivation across sub-groups of stakeholder representatives who are engaged across different social-ecological contexts. Questionnaire data collected among representatives at two governance levels, moose management groups (n = 624) and moose management units (n = 979), were subjected to two-step cluster analysis. The analyses revealed two sub-groups of representatives, characterized by differences in species composition and land ownership structure: managers of multi-ungulate areas and managers of large-carnivore areas. In several respects, these groups significantly differed in how they perceived the prerequisites. This included prerequisites of perceived competence with regard to their need for knowledge of topics and usefulness of monitoring methods, perceived autonomy operationalized as possibilities to perform their tasks with sufficient time, resources, and support from their organizations, and perceived relatedness to different groups of actors. Further efforts should be made to understand the conditions required for representatives to energize and direct their behavior. The institutional system must better fit the needs of stakeholder representatives across various local contexts, otherwise the space for local voluntary engagement might be hampered.
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