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  • 1. Abbasi, Saeed
    et al.
    Jansson, Anders
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Olander, Lars
    Olofsson, Ulf
    Sellgren, Ulf
    A pin-on-disc study of the rate of airborne wear particle emissions from railway braking materials2012In: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 284, p. 18-29Article in journal (Refereed)
    Abstract [en]

    The current study investigates the characteristics of particles generated from the wear of braking materials, and provides an applicable index for measuring and comparing wear particle emissions. A pin-on-disc tribometer equipped with particle measurement instruments was used. The number concentration, size, morphology, and mass concentration of generated particles were investigated and reported for particles 10 nm-32 mu m in diameter. The particles were also collected on filters and investigated using EDS and SEM. The effects of wear mechanisms on particle morphology and changes in particle concentration are discussed. A new index, the airborne wear particle emission rate (AWPER), is suggested that could be used in legislation to control non-exhaust emissions from transport modes, particularly rail transport.

  • 2. Abbasi, Saeed
    et al.
    Olander, Lars
    Larsson, Christina
    Olofsson, Ulf
    Jansson, Anders
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Sellgren, Ulf
    A field test study of airborne wear particles from a running regional train2012In: Proceedings of the Institution of mechanical engineers. Part F, journal of rail and rapid transit, ISSN 0954-4097, E-ISSN 2041-3017, Vol. 226, no 1, p. 95-109Article in journal (Refereed)
    Abstract [en]

    Inhalable airborne particles have inverse health effects. In railways, mechanical brakes, the wheel–rail contact, current collectors, ballast, sleepers, and masonry structures yield particulate matter. Field tests examined a Swedish track using a train instrumented with particle measurement devices, brake pad temperature sensors, and speed and brake sensors. The main objective of this field test was to study the characteristics of particles generated from disc brakes on a running train with an on-board measuring set-up. Two airborne particle sampling points were designated, one near a pad–rotor disc brake contact and a second under the frame, not near a mechanical brake or the wheel–rail contact; the numbers and size distributions of the particles detected were registered and evaluated under various conditions (e.g. activating/deactivating electrical brakes or negotiating curves). During braking, three speed/temperature-dependent particle peaks were identified in the fine region, representing particles 280, 350, and 600 nm in diameter. In the coarse region, a peak was discerned for particles 3–6 µm in diameter. Effects of brake pad temperature on particle size distribution were also investigated. Results indicate that the 280 nm peak increased with increasing temperature, and that electrical braking significantly reduced airborne particle numbers. Field emission scanning electron microscope images captured particles sizing down to 50 nm. The inductively coupled plasma mass spectrometry results indicated that Fe, Cu, Zn, Al, Ca, and Mg were the main elements constituting the particles.

  • 3. Abu-Omar, Mahdi M.
    et al.
    Barta, Katalin
    Beckham, Gregg T.
    Luterbacher, Jeremy S.
    Ralph, John
    Rinaldi, Roberto
    Román-Leshkov, Yuriy
    Samec, Joseph S. M.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Sels, Bert F.
    Wang, Feng
    Guidelines for performing lignin-first biorefining2021In: Energy & Environmental Science, ISSN 1754-5692, E-ISSN 1754-5706, Vol. 14, no 1, p. 262-292Article, review/survey (Refereed)
    Abstract [en]

    The valorisation of the plant biopolymer lignin is now recognised as essential to enabling the economic viability of the lignocellulosic biorefining industry. In this context, the lignin-first biorefining approach, in which lignin valorisation is considered in the design phase, has demonstrated the fullest utilisation of lignocellulose. We define lignin-first methods as active stabilisation approaches that solubilise lignin from native lignocellulosic biomass while avoiding condensation reactions that lead to more recalcitrant lignin polymers. This active stabilisation can be accomplished by solvolysis and catalytic conversion of reactive intermediates to stable products or by protection-group chemistry of lignin oligomers or reactive monomers. Across the growing body of literature in this field, there are disparate approaches to report and analyse the results from lignin-first approaches, thus making quantitative comparisons between studies challenging. To that end, we present herein a set of guidelines for analysing critical data from lignin-first approaches, including feedstock analysis and process parameters, with the ambition of uniting the lignin-first research community around a common set of reportable metrics. These guidelines comprise standards and best practices or minimum requirements for feedstock analysis, stressing reporting of the fractionation efficiency, product yields, solvent mass balances, catalyst efficiency, and the requirements for additional reagents such as reducing, oxidising, or capping agents. Our goal is to establish best practices for the research community at large primarily to enable direct comparisons between studies from different laboratories. The use of these guidelines will be helpful for the newcomers to this field and pivotal for further progress in this exciting research area.

  • 4.
    Ahrens, Maryon
    et al.
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Bohm, Christian
    Stockholm University, Faculty of Science, Department of Physics.
    Deoskar, Kunal
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Finley, Chad
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Hultqvist, Klas
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    O'Sullivan, Erin
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Walck, Christian
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Computational techniques for the analysis of small signals in high-statistics neutrino oscillation experiments2020In: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, ISSN 0168-9002, E-ISSN 1872-9576, Vol. 977, article id 164332Article in journal (Refereed)
    Abstract [en]

    The current and upcoming generation of Very Large Volume Neutrino Telescopes - collecting unprecedented quantities of neutrino events - can be used to explore subtle effects in oscillation physics, such as (but not restricted to) the neutrino mass ordering. The sensitivity of an experiment to these effects can be estimated from Monte Carlo simulations. With the high number of events that will be collected, there is a trade-off between the computational expense of running such simulations and the inherent statistical uncertainty in the determined values. In such a scenario, it becomes impractical to produce and use adequately-sized sets of simulated events with traditional methods, such as Monte Carlo weighting. In this work we present a staged approach to the generation of expected distributions of observables in order to overcome these challenges. By combining multiple integration and smoothing techniques which address limited statistics from simulation it arrives at reliable analysis results using modest computational resources.

  • 5. Ainsbury, Elizabeth A.
    et al.
    Higueras, Manuel
    Puig, Pedro
    Einbeck, Jochen
    Samaga, Daniel
    Francesc Barquinero, Joan
    Barrios, Lleonard
    Brzozowska, Beata
    Stockholm University, Faculty of Science, Department of Molecular Biosciences, The Wenner-Gren Institute. University of Warsaw, Poland.
    Fattibene, Paola
    Gregoire, Eric
    Jaworska, Alicja
    Lloyd, David
    Oestreicher, Ursula
    Romm, Horst
    Rothkamm, Kai
    Roy, Laurence
    Sommer, Sylwester
    Terzoudi, Georgia
    Thierens, Hubert
    Trompier, Francois
    Vral, Anne
    Woda, Clemens
    Uncertainty of fast biological radiation dose assessment for emergency response scenarios2017In: International Journal of Radiation Biology, ISSN 0955-3002, E-ISSN 1362-3095, Vol. 93, no 1, p. 127-135Article in journal (Refereed)
    Abstract [en]

    Purpose: Reliable dose estimation is an important factor in appropriate dosimetric triage categorization of exposed individuals to support radiation emergency response. Materials and methods: Following work done under the EU FP7 MULTIBIODOSE and RENEB projects, formal methods for defining uncertainties on biological dose estimates are compared using simulated and real data from recent exercises. Results: The results demonstrate that a Bayesian method of uncertainty assessment is the most appropriate, even in the absence of detailed prior information. The relative accuracy and relevance of techniques for calculating uncertainty and combining assay results to produce single dose and uncertainty estimates is further discussed. Conclusions: Finally, it is demonstrated that whatever uncertainty estimation method is employed, ignoring the uncertainty on fast dose assessments can have an important impact on rapid biodosimetric categorization.

  • 6. Ainsbury, Elizabeth
    et al.
    Badie, Christophe
    Barnard, Stephen
    Manning, Grainne
    Moquet, Jayne
    Abend, Michael
    Antunes, Ana Catarina
    Barrios, Lleonard
    Bassinet, Celine
    Beinke, Christina
    Bortolin, Emanuela
    Bossin, Lily
    Bricknell, Clare
    Brzoska, Kamil
    Buraczewska, Iwona
    Huertas Castano, Carlos
    Cemusova, Zina
    Christiansson, Maria
    Mateos Cordero, Santiago
    Coster, Guillaume
    Della Monac, Sara
    Desangles, Francois
    Discher, Michael
    Dominguez, Inmaculada
    Doucha-Senf, Sven
    Eakins, Jon
    Fattibene, Paola
    Filippi, Silvia
    Frenzel, Monika
    Georgieva, Dimka
    Gregoire, Eric
    Guogyte, Kamile
    Hadjidekova, Valeria
    Hadjiiska, Ljubomira
    Hristova, Rositsa
    Karakosta, Maria
    Kis, Eniko
    Kriehuber, Ralf
    Lee, Jungil
    Lloyd, David
    Lumniczky, Katalin
    Lyng, Fiona
    Macaeva, Ellina
    Majewski, Matthaeus
    Vanda Martins, S.
    McKeever, Stephen W. S.
    Meade, Aidan
    Medipally, Dinesh
    Meschini, Roberta
    M'kacher, Radhia
    Gil, Octavia Monteiro
    Montero, Alegria
    Moreno, Mercedes
    Noditi, Mihaela
    Oestreicher, Ursula
    Oskamp, Dominik
    Palitti, Fabrizio
    Palma, Valentina
    Pantelias, Gabriel
    Pateux, Jerome
    Patrono, Clarice
    Pepe, Gaetano
    Port, Matthias
    Jesus Prieto, Maria
    Quattrini, Maria Cristina
    Quintens, Roel
    Ricoul, Michelle
    Roy, Laurence
    Sabatier, Laure
    Sebastia, Natividad
    Sholom, Sergey
    Sommer, Sylwester
    Staynova, Albena
    Strunz, Sonja
    Terzoudi, Georgia
    Testa, Antonella
    Trompier, Francois
    Valente, Marco
    Van Hoey, Olivier
    Veronese, Ivan
    Wojcik, Andrzej
    Stockholm University, Faculty of Science, Department of Molecular Biosciences, The Wenner-Gren Institute.
    Woda, Clemens
    Integration of new biological and physical retrospective dosimetry methods into EU emergency response plans - joint RENEB and EURADOS inter-laboratory comparisons2017In: International Journal of Radiation Biology, ISSN 0955-3002, E-ISSN 1362-3095, Vol. 93, no 1, p. 99-109Article in journal (Refereed)
    Abstract [en]

    Purpose: RENEB, 'Realising the European Network of Biodosimetry and Physical Retrospective Dosimetry,' is a network for research and emergency response mutual assistance in biodosimetry within the EU. Within this extremely active network, a number of new dosimetry methods have recently been proposed or developed. There is a requirement to test and/or validate these candidate techniques and inter-comparison exercises are a well-established method for such validation. Materials and methods: The authors present details of inter-comparisons of four such new methods: dicentric chromosome analysis including telomere and centromere staining; the gene expression assay carried out in whole blood; Raman spectroscopy on blood lymphocytes, and detection of radiation induced thermoluminescent signals in glass screens taken from mobile phones. Results: In general the results show good agreement between the laboratories and methods within the expected levels of uncertainty, and thus demonstrate that there is a lot of potential for each of the candidate techniques. Conclusions: Further work is required before the new methods can be included within the suite of reliable dosimetry methods for use by RENEB partners and others in routine and emergency response scenarios.

  • 7. Antosz, Patrycja
    et al.
    Rembiasz, Tomasz
    Verhagen, Harko
    Stockholm University, Faculty of Social Sciences, Department of Computer and Systems Sciences.
    Employee shirking and overworking: modelling the unintended consequences of work organisation2020In: Ergonomics, ISSN 0014-0139, E-ISSN 1366-5847, Vol. 63, no 8, p. 997-1009Article in journal (Refereed)
    Abstract [en]

    Underworking (i.e. shirking) and overworking of employees can have detrimental effects for the individual and the organisation. We develop a computational model to investigate how work structure, specifically the way in which managers distribute work tasks amongst employees, impacts work intensity and working time. The model draws on theories from economics, psychology and management, and on empirical observations. The simulations show that when managers correctly estimate task difficulty, but undervalue the employee's competence, opportunities for shirking are provided due to longer deadlines. Similarly, if managers overvalue the employee's competence, they set tighter deadlines leading to overwork. If task difficulty is misjudged, initially only influence on employee working time is observed. However, it gradually generates competence misjudgements, indirectly impacting the employee's effort level. An interaction between competence misjudgement and task uncertainty slows the manager's ability to correctly estimate employee competence and prolongs initial competence misjudgements. The study highlights the importance of applying dynamic modelling methods, which allows for testing theory assumptions in silico, generating new hypotheses and offers a foundation for future research. Practitioner summary: A computational model was developed to investigate how the structure of work allocation influences opportunities for shirking and overworking by employees. The paper demonstrates how dynamic modelling can be used to explain workplace phenomena and develop new hypotheses for further research.

  • 8. Ashraf, M.
    et al.
    Wehgal, A. R.
    Stockholm University, Faculty of Science, Department of Mathematics. Bahauddin Zakariya University, Pakistan.
    MHD flow and heat transfer of micropolar fluid between two porous disks2012In: Applied mathematics and mechanics, ISSN 0253-4827, E-ISSN 1573-2754, Vol. 33, no 1, p. 51-64Article in journal (Refereed)
    Abstract [en]

    A numerical study is carried out for the axisymmetric steady laminar incompressible flow of an electrically conducting micropolar fluid between two infinite parallel porous disks with the constant uniform injection through the surface of the disks. The fluid is subjected to an external transverse magnetic field. The governing nonlinear equations of motion are transformed into a dimensionless form through von Karman's similarity transformation. An algorithm based on a finite difference scheme is used to solve the reduced coupled ordinary differential equations under associated boundary conditions. The effects of the Reynolds number, the magnetic parameter, the micropolar parameter, and the Prandtl number on the flow velocity and temperature distributions are discussed. The results agree well with those of the previously published work for special cases. The investigation predicts that the heat transfer rate at the surfaces of the disks increases with the increases in the Reynolds number, the magnetic parameter, and the Prandtl number. The shear stresses decrease with the increase in the injection while increase with the increase in the applied magnetic field. The shear stress factor is lower for micropolar fluids than for Newtonian fluids, which may be beneficial in the flow and thermal control in the polymeric processing.

  • 9.
    Axelsson, Magnus
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Hitomi (ASTRO-H) X-ray Astronomy Satellite2018In: Journal of Astronomical Telescopes Instruments and Systems, ISSN 2329-4124, Vol. 4, no 2, article id 021402Article in journal (Refereed)
    Abstract [en]

    The Hitomi (ASTRO-H) mission is the sixth Japanese x-ray astronomy satellite developed by a large international collaboration, including Japan, USA, Canada, and Europe. The mission aimed to provide the highest energy resolution ever achieved at E > 2 keV, using a microcalorimeter instrument, and to cover a wide energy range spanning four decades in energy from soft x-rays to gamma rays. After a successful launch on February 17, 2016, the spacecraft lost its function on March 26, 2016, but the commissioning phase for about a month provided valuable information on the onboard instruments and the spacecraft system, including astrophysical results obtained from first light observations. The paper describes the Hitomi (ASTRO-H) mission, its capabilities, the initial operation, and the instruments/spacecraft performances confirmed during the commissioning operations for about a month.

  • 10. Battistin, Claudia
    et al.
    Hertz, John
    Stockholm University, Nordic Institute for Theoretical Physics (Nordita). Niels Bohr Institute, Denmark.
    Tyrcha, Joanna
    Stockholm University, Faculty of Science, Department of Mathematics.
    Roudi, Yasser
    Stockholm University, Nordic Institute for Theoretical Physics (Nordita). Kavli Institute for Systems Neuroscience/Centre for Neural Computation, Norway.
    Belief propagation and replicas for inference and learning in a kinetic Ising model with hidden spins2015In: Journal of Statistical Mechanics: Theory and Experiment, E-ISSN 1742-5468, article id P05021Article in journal (Refereed)
    Abstract [en]

    We propose a new algorithm for inferring the state of hidden spins and reconstructing the connections in a synchronous kinetic Ising model, given the observed history. Focusing on the case in which the hidden spins are conditionally independent of each other given the state of observable spins, we show that calculating the likelihood of the data can be simplified by introducing a set of replicated auxiliary spins. Belief propagation (BP) and susceptibility propagation (SusP) can then be used to infer the states of hidden variables and to learn the couplings. We study the convergence and performance of this algorithm for networks with both Gaussian-distributed and binary bonds. We also study how the algorithm behaves as the fraction of hidden nodes and the amount of data are changed, showing that it outperforms the Thouless-Anderson-Palmer (TAP) equations for reconstructing the connections.

  • 11.
    Bhatnagar, Akshay
    et al.
    Stockholm University, Nordic Institute for Theoretical Physics (Nordita).
    Pandey, Vikash
    Perlekar, Prasad
    Mitra, Dhrubaditya
    Stockholm University, Nordic Institute for Theoretical Physics (Nordita).
    Rate of formation of caustics in heavy particles advected by turbulence2022In: Philosophical Transactions. Series A: Mathematical, physical, and engineering science, ISSN 1364-503X, E-ISSN 1471-2962, Vol. 380, no 2219, article id 20210086Article in journal (Refereed)
    Abstract [en]

    The rate of collision and the relative velocities of the colliding particles in turbulent flows are a crucial part of several natural phenomena, e.g. rain formation in warm clouds and planetesimal formation in protoplanetary discs. The particles are often modelled as passive, but heavy and inertial. Within this model, large relative velocities emerge due to formation of singularities (caustics) of the gradient matrix of the velocities of the particles. Using extensive direct numerical simulations of heavy particles in both two (direct and inverse cascade) and three-dimensional turbulent flows, we calculate the rate of formation of caustics, J as a function of the Stokes number (St). The best approximation to our data is J∼exp(−C/St), in the limit St→0 where C is a non-universal constant.

  • 12.
    Bo, Stefano
    et al.
    Stockholm University, Nordic Institute for Theoretical Physics (Nordita).
    Lim, Soon Hoe
    Stockholm University, Nordic Institute for Theoretical Physics (Nordita).
    Eichhorn, Ralf
    Stockholm University, Nordic Institute for Theoretical Physics (Nordita).
    Functionals in stochastic thermodynamics: how to interpret stochastic integrals2019In: Journal of Statistical Mechanics: Theory and Experiment, E-ISSN 1742-5468, article id 084005Article in journal (Refereed)
    Abstract [en]

    In stochastic thermodynamics standard concepts from macroscopic thermodynamics, such as heat, work, and entropy production, are generalized to small fluctuating systems by defining them on a trajectory-wise level. In Langevin systems with continuous state-space such definitions involve stochastic integrals along system trajectories, whose specific values depend on the discretization rule used to evaluate them (i.e. the 'interpretation' of the noise terms in the integral). Via a systematic mathematical investigation of this apparent dilemma, we corroborate the widely used standard interpretation of heat-and work-like functionals as Stratonovich integrals. We furthermore recapitulate the anomalies that are known to occur for entropy production in the presence of temperature gradients.

  • 13.
    Bodin Danielsson, Christina
    Stockholm University, Faculty of Social Sciences, Stress Research Institute.
    Vad är ett bra kontor?: olika perspektiv på Sveriges vanligaste arbetsplats2014 (ed. 1)Book (Other (popular science, discussion, etc.))
  • 14. Bogunovic, Lukas
    et al.
    Fliedner, Marc
    Eichhorn, Ralf
    Stockholm University, Nordic Institute for Theoretical Physics (Nordita).
    Wegener, Sonja
    Regtmeier, Jan
    Anselmetti, Dario
    Reimann, Peter
    Chiral Particle Separation by a Nonchiral Microlattice2012In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 109, no 10, p. 100603-Article in journal (Refereed)
    Abstract [en]

    We conceived a model experiment for a continuous separation strategy of chiral molecules (enantiomers) without the need of any chiral selector structure or derivatization agents: Microparticles that only differ by their chirality are shown to migrate along different directions when driven by a steady fluid flow through a square lattice of cylindrical posts. In accordance with our numerical predictions, the transport directions of the enantiomers depend very sensitively on the orientation of the lattice relative to the fluid flow.

  • 15. Bolin, Karl
    et al.
    Bluhm, Gosta
    Nilsson, Mats E.
    Stockholm University, Faculty of Social Sciences, Department of Psychology. Karolinska Institutet, Sweden.
    Listening Test Comparing A-Weighted and C-Weighted Sound Pressure Level as Indicator of Wind Turbine Noise Annoyance2014In: Acta Acoustica united with Acustica, ISSN 1610-1928, E-ISSN 1861-9959, Vol. 100, no 5, p. 842-847Article in journal (Refereed)
    Abstract [en]

    A listening test was conducted to investigate whether A-or C-weighed sound levels are most suitable as indicator of annoyance due to wind turbine noise. The tests consisted of fifteen different wind turbine noises presented at eight sound levels together with pink noise signals as reference sounds. A total number of 31 persons performed the listening test divided into two subgroups. The first group comprising of 20 students conducted the test in a semi anechoic chamber, and the second group of 11 residents annoyed by wind turbine noise in their homes, conducted the test in their own homes. Results from both subgroups showed that A-weighed sound levels were a more accurate description of wind turbine noise annoyance than C-weighed sound levels. The residents found the same wind turbine noises more annoying than the students, indicating a higher sensitivity to wind turbine noise among persons a priori annoyed by this noise and exposed to this source in their residential settings.

  • 16. Boman, Christoffer
    et al.
    Pettersson, Esbjorn
    Westerholm, Roger
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Bostrom, Dan
    Nordin, Anders
    Stove Performance and Emission Characteristics in Residential Wood Log and Pellet Combustion, Part 1: Pellet Stoves2011In: Energy & Fuels, ISSN 0887-0624, E-ISSN 1520-5029, Vol. 25, p. 307-314Article in journal (Refereed)
    Abstract [en]

    Stove performance, characteristics, and quantities of gaseous and particulate emissions were determined for two different pellet stoves, varying fuel load, pellet diameter, and chimney draft. This approach aimed at covering variations in emissions from stoves in use today. The extensive measurement campaign included CO, NO(x), organic gaseous carbon, volatile organic compounds (VOCs), polycyclic aromatic hydrocarbons (PAHs), total particulate matter (PM(tot)) as well as particle mass and number concentrations, size distributions, and inorganic composition. At high load, most emissions were similar. For stove B, operating at high residual oxygen and solely with primary air, the emissions of PM,, and particle numbers were higher while the particles were smaller. Lowering the fuel load, the emissions of CO and hydrocarbons increased dramatically for stove A, which operated continuously also at lower fuel loads. On the other hand for stove B, which had intermittent operation at lower fuel loads, the emissions of hydrocarbons increased only slightly lowering the fuel load, while CO emissions increased sharply, due to high emissions at the end of the combustion cycle. Beside methane, dominating VOCs were ethene, acetylene, and benzene and the emissions of VOC varied in the range 1.1-42 mg/MJ(fuel). PAH emissions (2-340 mu g/MJ(fuel)) were generally dominated by phenanthrene, fluoranthene and pyrene. The PM(tot) values (15-45 mg/MJ(fuel)) were in all cases dominated by fine particles with mass median diameters in the range 100-200 nm, peak mobility diameters of 50-85 nm, and number concentrations in the range 4 x 10(13) to 3 x 10(14) particles/MJ(fuel). During high load conditions, the particulate matter was totally dominated by inorganic particles at 15-25 mg/MJ(fuel) consisting of potassium, sodium, sulfur, and chlorine, in the form of K(2)SO(4), K(3)Na(SO(4))(2), and KCl. The study shows that differences in operation and modulation principles for the tested pellet stoves, relevant for appliances in use today, will affect the performance and emissions significantly, although with lower scattering in the present study compared to compiled literature data.

  • 17.
    Bonfils, Anthony F.
    et al.
    Stockholm University, Nordic Institute for Theoretical Physics (Nordita).
    Mitra, Dhrubaditya
    Stockholm University, Nordic Institute for Theoretical Physics (Nordita).
    Moon, Woosok
    Stockholm University, Nordic Institute for Theoretical Physics (Nordita). Stockholm University, Faculty of Science, Department of Mathematics.
    Wettlaufer, John S.
    Stockholm University, Nordic Institute for Theoretical Physics (Nordita).
    Asymptotic interpretation of the Miles mechanism of wind-wave instability2022In: Journal of Fluid Mechanics, ISSN 0022-1120, E-ISSN 1469-7645, Vol. 944, article id A8Article in journal (Refereed)
    Abstract [en]

    When wind blows over water, ripples are generated on the water surface. These ripples can be regarded as perturbations of the wind field, which is modelled as a parallel inviscid flow. For a given wavenumber k, the perturbed streamfunction of the wind field and the complex phase speed are the eigenfunction and the eigenvalue of the so-called Rayleigh equation in a semi-infinite domain. Because of the small air–water density ratio, ρa/ρw≡ϵ≪1, the wind and the ripples are weakly coupled, and the eigenvalue problem can be solved perturbatively. At the leading order, the eigenvalue is equal to the phase speed c0 of surface waves. At order ϵ, the eigenvalue has a finite imaginary part, which implies growth. Miles (J. Fluid Mech., vol. 3, 1957, pp. 185–204) showed that the growth rate is proportional to the square modulus of the leading-order eigenfunction evaluated at the so-called critical level z=zc, where the wind speed is equal to c0 and the waves extract energy from the wind. Here, we construct uniform asymptotic approximations of the leading-order eigenfunction for long waves, which we use to calculate the growth rate as a function of k. In the strong wind limit, we find that the fastest growing wave is such that the aerodynamic pressure is in phase with the wave slope. The results are confirmed numerically.

  • 18.
    Bonfils, Anthony
    et al.
    Stockholm University, Nordic Institute for Theoretical Physics (Nordita).
    Mitra, Dhrubaditya
    Stockholm University, Nordic Institute for Theoretical Physics (Nordita).
    Moon, W.
    Wettlaufer, John
    Stockholm University, Nordic Institute for Theoretical Physics (Nordita). Yale University, USA.
    Flow-driven interfacial waves: an inviscid asymptotic study2023In: Journal of Fluid Mechanics, ISSN 0022-1120, E-ISSN 1469-7645, Vol. 976, article id A19Article in journal (Refereed)
    Abstract [en]

    Motivated by wind blowing over water, we use asymptotic methods to study the evolution of short wavelength interfacial waves driven by the combined action of these flows. We solve the Rayleigh equation for the stability of the shear flow, and construct a uniformly valid approximation for the perturbed streamfunction, or eigenfunction. We then expand the real part of the eigenvalue, the phase speed, in a power series of the inverse wavenumber and show that the imaginary part is exponentially small. We give expressions for the growth rates of the Miles (J. Fluid Mech., vol. 3, 1957, pp. 185–204) and rippling (e.g. Young & Wolfe, J. Fluid Mech., vol. 739, 2014, pp. 276–307) instabilities that are valid for an arbitrary shear flow. The accuracy of the results is demonstrated by a comparison with the exact solution of the eigenvalue problem in the case when both the wind and the current have an exponential profile.

  • 19.
    Brandenburg, Axel
    et al.
    Stockholm University, Nordic Institute for Theoretical Physics (Nordita). Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC). School of Natural Sciences and Medicine, Ilia State University, Georgia; McWilliams Center for Cosmology, Department of Physics, Carnegie Mellon University, USA.
    Protiti, Nousaba Nasrin
    Electromagnetic Conversion into Kinetic and Thermal Energies2023In: Entropy, E-ISSN 1099-4300, Vol. 25, no 9, article id 1270Article in journal (Refereed)
    Abstract [en]

    The conversion of electromagnetic energy into magnetohydrodynamic energy occurs when the electric conductivity changes from negligible to finite values. This process is relevant during the epoch of reheating in the early universe at the end of inflation and before the emergence of the radiation-dominated era. We find that the conversion into kinetic and thermal energies is primarily the result of electric energy dissipation, while magnetic energy only plays a secondary role in this process. This means that since electric energy dominates over magnetic energy during inflation and reheating, significant amounts of electric energy can be converted into magnetohydrodynamic energy when conductivity emerges before the relevant length scales become stable.

  • 20.
    Brzozowska, Beata
    et al.
    Stockholm University, Faculty of Science, Department of Molecular Biosciences, The Wenner-Gren Institute. University of Warsaw, Poland.
    Ainsbury, Elizabeth
    Baert, Annelot
    Beaton-Green, Lindsay
    Barrios, Leonardo
    Francesc Barquinero, Joan
    Bassinet, Celine
    Beinke, Christina
    Benedek, Anett
    Beukes, Philip
    Bortolin, Emanuela
    Buraczewska, Iwona
    Burbidge, Christopher
    De Amicis, Andrea
    De Angelis, Cinzia
    Della Monaca, Sara
    Depuydt, Julie
    De Sanctis, Stefania
    Dobos, Katalin
    Domene, Mercedes Moreno
    Dominguez, Inmaculada
    Facco, Eva
    Fattibene, Paola
    Frenzel, Monika
    Gil, Octavia Monteiro
    Gonon, Geraldine
    Gregoire, Eric
    Gruel, Gaetan
    Hadjidekova, Valeria
    Hatzi, Vasiliki I.
    Hristova, Rositsa
    Jaworska, Alicja
    Kis, Eniko
    Kowalska, Maria
    Kulka, Ulrike
    Lista, Florigio
    Lumniczky, Katalin
    Martinez-Lopez, Wilner
    Meschini, Roberta
    Moertl, Simone
    Moquet, Jayne
    Noditi, Mihaela
    Oestreicher, Ursula
    Orta Vazquez, Manuel Luis
    Palma, Valentina
    Pantelias, Gabriel
    Montoro Pastor, Alegria
    Patrono, Clarice
    Piqueret-Stephan, Laure
    Quattrini, Maria Cristina
    Regalbuto, Elisa
    Ricoul, Michelle
    Roch-Lefevre, Sandrine
    Roy, Laurence
    Sabatier, Laure
    Sarchiapone, Lucia
    Sebastia, Natividad
    Sommer, Sylwester
    Sun, Mingzhu
    Suto, Yumiko
    Terzoudi, Georgia
    Trompier, Francois
    Vral, Anne
    Wilkins, Ruth
    Zafiropoulos, Demetre
    Wieser, Albrecht
    Woda, Clemens
    Wojcik, Andrzej
    Stockholm University, Faculty of Science, Department of Molecular Biosciences, The Wenner-Gren Institute. Jan Kochanowski University, Poland.
    RENEB accident simulation exercise2017In: International Journal of Radiation Biology, ISSN 0955-3002, E-ISSN 1362-3095, Vol. 93, no 1, p. 75-80Article in journal (Refereed)
    Abstract [en]

    Purpose: The RENEB accident exercise was carried out in order to train the RENEB participants in coordinating and managing potentially large data sets that would be generated in case of a major radiological event. Materials and methods: Each participant was offered the possibility to activate the network by sending an alerting email about a simulated radiation emergency. The same participant had to collect, compile and report capacity, triage categorization and exposure scenario results obtained from all other participants. The exercise was performed over 27 weeks and involved the network consisting of 28 institutes: 21 RENEB members, four candidates and three non-RENEB partners. Results: The duration of a single exercise never exceeded 10 days, while the response from the assisting laboratories never came later than within half a day. During each week of the exercise, around 4500 samples were reported by all service laboratories (SL) to be examined and 54 scenarios were coherently estimated by all laboratories (the standard deviation from the mean of all SL answers for a given scenario category and a set of data was not larger than 3 patient codes). Conclusions: Each participant received training in both the role of a reference laboratory (activating the network) and of a service laboratory (responding to an activation request). The procedures in the case of radiological event were successfully established and tested.

  • 21. Bylund, Jonas
    What's The Problem With Non-conventional Technology?: The Stockholm Local Investment Programme and the Eco-cycling Districts2003In: Time to turn down energy demand / [ed] Sophie Attali, Eliane Métreau, Mélisande Prône, Kenya Tillerson, Stockholm: European Council for an Energy-Efficient Economy - ECEEE , 2003, p. 853-861Chapter in book (Refereed)
    Abstract [en]

    This paper analyses barriers towards implementation of non-conventional energy and resource efficient technology in the context of urban development. It gives tentative conclusions based on an ongoing Ph.D. dissertation project. The case is the measures the city of Stockholm launched with the help of a Swedish Governmental subsidy program – the Local Investment Program (LIP). The LIP runs from 1998 to 2003 and is intended to help municipalities nationwide adapt to the demands of an ecologically sustainable society. Measures that uses new, or in the terminology of this paper, non-conventional technology are explicitly supported in the program. Stockholm was granted 67 million Euro to subsidize different projects, among them the eco-cycling districts of Hammarby Sjöstad, Östberga and Skärholmen. Experiences reported by the municipal LIP co-ordinators nationwide are that only half of all the programs are realized as intended in the applications. As the project is work in progress this paper will try to answer the following questions: Why are some projects successful and others not? Why are sustainability-measures in these projects not carried out completely? Which agents and mediators do help or hinder the subsidies to become a realized and working technology in the city? What is the problem with non-conventional technology really? What parts does politics, policy and administrative practices as well as ‘rational’ economical behaviours play? Some old obstacles, but are new solutions dependent on unorthodox practice or simply more money? Knowledge on these issues is (still) important for subsequent policies and programs on energy and resource efficiency.

  • 22. Celani, Antonio
    et al.
    Bo, Stefano
    Eichhorn, Ralf
    Stockholm University, Nordic Institute for Theoretical Physics (Nordita).
    Aurell, Erik
    Anomalous Thermodynamics at the Microscale2012In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 109, no 26, p. 260603-Article in journal (Refereed)
    Abstract [en]

    Particle motion at the microscale is an incessant tug-of-war between thermal fluctuations and applied forces on one side and the strong resistance exerted by fluid viscosity on the other. Friction is so strong that completely neglecting inertia-the overdamped approximation-gives an excellent effective description of the actual particle mechanics. In sharp contrast to this result, here we show that the overdamped approximation dramatically fails when thermodynamic quantities such as the entropy production in the environment are considered, in the presence of temperature gradients. In the limit of vanishingly small, yet finite, inertia, we find that the entropy production is dominated by a contribution that is anomalous, i.e., has no counterpart in the overdamped approximation. This phenomenon, which we call an entropic anomaly, is due to a symmetry breaking that occurs when moving to the small, finite inertia limit. Anomalous entropy production is traced back to futile phase-space cyclic trajectories displaying a fast downgradient sweep followed by a slow upgradient return to the original position. DOI: 10.1103/PhysRevLett.109.260603

  • 23. Chen, Shuzhen
    et al.
    Pan, Yuchen
    Wu, Desheng
    Stockholm University, Faculty of Social Sciences, Stockholm Business School. University of Chinese Academy of Sciences, China.
    Dolgui, Alexandre
    In-house versus outsourcing collection in a closed-loop supply chain with remanufacturing technology development2023In: International Journal of Production Research, ISSN 0020-7543, E-ISSN 1366-588X, Vol. 61, no 6, p. 1720-1735Article in journal (Refereed)
    Abstract [en]

    This paper develops a game model of a closed-loop supply chain consisting of one manufacturer, one remanufacturer and one retailer and investigates the long-term collection strategies of the manufacturer who needs to cooperate with the remanufacturer to develop the remanufacturing technology. The game model is developed from a fully dynamic perspective on the remanufacturing technology development and analyzed using the system dynamics method. We identify the trade-off in the choice of collection strategies: the early entry in the remanufacturing industry versus the complete control in the later stage. The simulation results show that when the entry barrier to the remanufacturing industry is low, the manufacturer can develop the remanufacturing technology in a short time and the direct reverse channel outperforms the indirect reverse channel; when the entry barrier is high, the manufacturer can achieve more profits under the indirect reverse channel by acquiring the remanufacturing technology directly from the remanufacturer. Moreover, the indirect reverse channel is more likely to be superior for low-barrier remanufacturing industry when the cost advantage is high as the early entry in the remanufacturing industry becomes more important than the complete control in the later stage.

  • 24. Chen, Shuzhen
    et al.
    Wu, Desheng
    Stockholm University, Faculty of Social Sciences, Stockholm Business School. University of Chinese Academy of Sciences, China.
    A revealed damage cost method to evaluate environmental performance of production: Evaluating treatment efficiency of emissions and scaling treatment cost bounds2018In: Journal of Cleaner Production, ISSN 0959-6526, E-ISSN 1879-1786, Vol. 194, p. 101-111Article in journal (Refereed)
    Abstract [en]

    Environmental performance indices are in great demand for environmental policy support. This paper addresses the particular problem of evaluating environmental performance of industries and identifying the worst performed industries that should be strictly regulated. Specifically, an input-output analysis method is developed to disentangle the environmental pressures of production processes; treatment costs are introduced to reveal the damage costs of relevant pressures which is integrated in the DEA based index to restrict the weight assignment. The proposed method is advantageous in data requirements as well as definition of process boundaries and can alleviate the underestimation of damages from predominant pressures. The results of evaluation provide a more reliable reference to industrial regulation.

  • 25.
    Chen, Xi
    et al.
    Beijing Foreign Studies University, People’s Republic of China; University of Iowa, USA.
    Li, Kaiwen
    Beijing Foreign Studies University, People’s Republic of China.
    Lin, Sidian
    Harvard University, USA.
    Ding, Xiaosong
    Stockholm University, Faculty of Social Sciences, Department of Computer and Systems Sciences. Beijing Foreign Studies University, People’s Republic of China.
    Technician routing and scheduling with employees’ learning through implicit cross-training strategy2024In: International Journal of Production Economics, ISSN 0925-5273, E-ISSN 1873-7579, Vol. 271, article id 109208Article in journal (Refereed)
    Abstract [en]

    With record high talent shortages and skill mismatches around the world, this paper investigates a variant of multi-period dynamic technician and routing problem that can be modeled as a Markov decision process. To deal with the double tradeoffs between the routing and service time costs, as well as the current and future costs, we propose an approximate dynamic programming (ADP)-based cost function approximation (CFA) algorithm — the implicit cross-training strategy (ICT). A two-phase routing and scheduling heuristic is developed to account for both employees’ learning and future information, and to facilitate an efficient implementation of CFA. Extensive computational results show that ICT can provide a better solution in the current decision with a global view in comparison with the myopic strategy. In depth analysis demonstrates that ICT trains the workforce with more balanced skillsets and workloads, which ensures the flexibility of the workforce and helps buffer against the future uncertainties with substantial routing cost savings. Additionally, ICT has much more advantages in large-scale problems with more diversified service requests and randomly distributed customers.

  • 26. Dabelow, Lennart
    et al.
    Bo, Stefano
    Eichhorn, Ralf
    Stockholm University, Nordic Institute for Theoretical Physics (Nordita).
    How irreversible are steady-state trajectories of a trapped active particle?2021In: Journal of Statistical Mechanics: Theory and Experiment, E-ISSN 1742-5468, Vol. 2021, no 3, article id 033216Article in journal (Refereed)
    Abstract [en]

    The defining feature of active particles is that they constantly propel themselves by locally converting chemical energy into directed motion. This active self-propulsion prevents them from equilibrating with their thermal environment (e.g. an aqueous solution), thus keeping them permanently out of equilibrium. Nevertheless, the spatial dynamics of active particles might share certain equilibrium features, in particular in the steady state. We here focus on the time-reversal symmetry of individual spatial trajectories as a distinct equilibrium characteristic. We investigate to what extent the steady-state trajectories of a trapped active particle obey or break this time-reversal symmetry. Within the framework of active Ornstein-Uhlenbeck particles we find that the steady-state trajectories in a harmonic potential fulfill path-wise time-reversal symmetry exactly, while this symmetry is typically broken in anharmonic potentials.

  • 27. Dai, Peng
    et al.
    Chen, Zheng
    Gan, Xiaohua
    Liberman, Mikhail A.
    Stockholm University, Nordic Institute for Theoretical Physics (Nordita).
    Autoignition and detonation development from a hot spot inside a closed chamber: Effects of end wall reflection2021In: Proceedings of the Combustion Institute, ISSN 1540-7489, E-ISSN 1873-2704, Vol. 38, no 4, p. 5905-5913Article in journal (Refereed)
    Abstract [en]

    The advancement of highly boosted internal combustion engines (ICEs) with high thermal efficiency is mainly constrained by knock and super-knock, respectively, due to the end gas autoignition and detonation development. The pressure wave propagation and reflection in a small confined space may strongly interact with local end gas autoignition, leading to combustion characteristics different from those in a large chamber or open space. The present study investigates the transient autoignition process in an iso-octane/air mixture inside a closed chamber under engine-relevant conditions. The emphasis is given to the assessment of effects of the pressure wave-wall reflection and the mechanism of extremely strong pressure oscillation typical for super-knock. It is found that the hot spot induced autoignition in a closed chamber can be greatly affected by shock/pressure wave reflection from the end wall. Different autoignition modes respectively from the hot spot and the end wall reflection are identified. A non-dimensional parameter quantifying the interplay between different length and time scales is introduced, which helps to identify different autoignition regimes including detonation development near the end wall. It is shown that detonation development from the hot spot may cause super-knock with devastating pressure oscillation. However, the detonation development from the end wall can hardly produce pressure oscillation strong enough for the super-knock. The obtained results provide a fundamental insight into the knocking mechanism in engines under highly boosted conditions.

  • 28. De Marchis, M.
    et al.
    Milici, B.
    Sardina, Gaetano
    Stockholm University, Faculty of Science, Department of Meteorology .
    Napoli, E.
    Interaction between turbulent structures and particles in roughened channel2016In: International Journal of Multiphase Flow, ISSN 0301-9322, E-ISSN 1879-3533, Vol. 78, p. 117-131Article in journal (Refereed)
    Abstract [en]

    The distribution of inertial particles in turbulent flows is highly non-uniform and is driven by the local dynamics of the turbulent structures of the underlying carrier flow field. In the specific context of dilute particle-laden wall-bounded flows, deposition and resuspension mechanisms are dominated by the interaction between inertial particles and coherent turbulent structures characteristic of the wall region. The macroscopic behavior of these two-phase systems is influenced by particle inertia, which plays a role at the microscale of a single dispersed element. These turbulent structures, which control the turbulent regeneration cycles, are strongly affected by the wall roughness. The effect of the roughness on turbulent transport in dilute suspension has been still poorly investigated. The issue is discussed here by addressing direct numerical simulation (DNS), at friction Reynolds number Re-tau = 180, of a dilute dispersion of heavy particles in a turbulent channel flow, spanning two orders of magnitude of particle inertia. The irregular wall roughness is obtained through the superimposition of four sinusoidal functions of different wavelengths and random amplitudes. We use DNS combined with Lagrangian particle tracking to characterize the effect of inertia on particle preferential accumulation, looking at the effect of roughness on particle distribution, by comparing the statistics computed for fluid and particles of different size and observing differences in terms of distribution patterns and preferential sampling.

  • 29. De, Sadhitro
    et al.
    Mitra, Dhrubaditya
    Stockholm University, Nordic Institute for Theoretical Physics (Nordita).
    Pandit, Rahul
    Uncovering the multifractality of Lagrangian pair dispersion in shock-dominated turbulence2024In: Physical Review Research, E-ISSN 2643-1564, Vol. 6, no 2, article id L022032Article in journal (Refereed)
    Abstract [en]

    Lagrangian pair dispersion provides insights into mixing in turbulent flows. By direct numerical simulations (DNSs) we show that the statistics of pair dispersion in the randomly forced two-dimensional Burgers equation, which is a typical model of shock -dominated turbulence, is very different from its incompressible counterpart because Lagrangian particles get trapped in shocks. We develop a heuristic theoretical framework that accounts for this-a generalization of the multifractal model-whose prediction of the scaling of Lagrangian exit times agrees well with our DNS.

  • 30.
    Deperas-Kaminska, Marta
    et al.
    Stockholm University, Faculty of Science, Department of Molecular Biosciences, The Wenner-Gren Institute. Institute of Mother and Child, Poland.
    Bajinskis, Ainars
    Stockholm University, Faculty of Science, Department of Molecular Biosciences, The Wenner-Gren Institute. University of Latvia, Latvia.
    Marczyk, Michal
    Polanska, Joanna
    Wersäll, Peter
    Lidbrink, Elisabet
    Ainsbury, Elizabeth A.
    Guipaud, Oliver
    Benderitter, Marc
    Haghdoost, Siamak
    Stockholm University, Faculty of Science, Department of Molecular Biosciences, The Wenner-Gren Institute.
    Wojcik, Andrzej
    Stockholm University, Faculty of Science, Department of Molecular Biosciences, The Wenner-Gren Institute. Jan Kochanowski University, Poland.
    RADIATION-INDUCED CHANGES IN LEVELS OF SELECTED PROTEINS IN PERIPHERAL BLOOD SERUM OF BREAST CANCER PATIENTS AS A POTENTIAL TRIAGE BIODOSIMETER FOR LARGE-SCALE RADIOLOGICAL EMERGENCIES2014In: Health Physics, ISSN 0017-9078, E-ISSN 1538-5159, Vol. 107, no 6, p. 555-563Article in journal (Refereed)
    Abstract [en]

    The threat of a large scale radiological emergency, where thousands of people may require fast biological dosimetry for the purpose of triage, makes it necessary to search for new, high throughput biological dosimeters. The authors tested an assay based on the quantitative analysis of selected proteins in peripheral blood serum. They were particularly interested in testing proteins that are specific to irradiation of skin, as these can be used in cases of partial body exposure. Candidate proteins were identified in an earlier study with mice, where skin of the animals was exposed to different doses of radiation and global expression of serum proteins was analyzed. Eight proteins were found, the expression of which showed a consistent dose-response relationship. Human analogues of these proteins were identified, and their expression was measured in peripheral blood serum of 16 breast cancer patients undergoing external beam radiotherapy. The proteins were Apolipoprotein E; Apolipoprotein H; Complement protein 7; Prothrombinase; Pantothenate Kinase 4; Alpha-2-macroglobulin; Fetuin B and Alpha-1-Anti-Chymotrypsin. Measurements were carried out in blood samples collected prior to exposure (control), on the day after one fraction (2 Gy), on the day after five fractions (10 Gy), on the day after 10 fractions (20 Gy), and 1 mo after 23-25 fractions (total dose of 46-50 Gy). Multivariate analysis was carried out, and a multinomial logistic regression model was built. The results indicate that the combined analysis of Apolipoprotein E, Factor X, and Pantothenate Kinase 4 allows discriminating between exposure to 2 Gy and lower and between 10 Gy and higher. The discrimination is possible up to 1 mo after exposure.

  • 31. Depuydt, Julie
    et al.
    Baeyens, Ans
    Barnard, Stephen
    Beinke, Christina
    Benedek, Anett
    Beukes, Philip
    Buraczewska, Iwona
    Darroudi, Firouz
    De Sanctis, Stefania
    Domingue, Inmaculada
    Gil, Octavia Monteiro
    Hadjidekova, Valeria
    Kis, Eniko
    Kulka, Ulrike
    Lista, Florigio
    Lumniczky, Katalin
    M'kacher, Radhia
    Moquet, Jayne
    Obreja, Doina
    Oestreicher, Ursula
    Pajic, Jelena
    Pastor, Nuria
    Popova, Ljubomira
    Regalbuto, Elisa
    Ricoul, Michelle
    Sabatier, Laure
    Slabbert, Jacobus
    Sommer, Sylwester
    Testa, Antonella
    Thierens, Hubert
    Wojcik, Andrzej
    Stockholm University, Faculty of Science, Department of Molecular Biosciences, The Wenner-Gren Institute.
    Vral, Anne
    RENEB intercomparison exercises analyzing micronuclei (Cytokinesis-block Micronucleus Assay)2017In: International Journal of Radiation Biology, ISSN 0955-3002, E-ISSN 1362-3095, Vol. 93, no 1, p. 36-47Article in journal (Refereed)
    Abstract [en]

    Purpose: In the framework of the 'Realizing the European Network of Biodosimetry' (RENEB) project, two intercomparison exercises were conducted to assess the suitability of an optimized version of the cytokinesis-block micronucleus assay, and to evaluate the capacity of a large laboratory network performing biodosimetry for radiation emergency triages. Twelve European institutions participated in the first exercise, and four non-RENEB labs were added in the second one. Materials and methods: Irradiated blood samples were shipped to participating labs, whose task was to culture these samples and provide a blind dose estimate. Micronucleus analysis was performed by automated, semi-automated and manual procedures. Results: The dose estimates provided by network laboratories were in good agreement with true administered doses. The most accurate estimates were reported for low dose points (<= 0.94 Gy). For higher dose points (>= 2.7 Gy) a larger variation in estimates was observed, though in the second exercise the number of acceptable estimates increased satisfactorily. Higher accuracy was achieved with the semi-automated method. Conclusion: The results of the two exercises performed by our network demonstrate that the micronucleus assay is a useful tool for large-scale radiation emergencies, and can be successfully implemented within a large network of laboratories.

  • 32.
    Ding, Xiaosong
    et al.
    Stockholm University, Faculty of Social Sciences, Department of Computer and Systems Sciences. Beijing Foreign Studies University, People’s Republic of China.
    Feng, Chong
    Yu, Peiling
    Li, Kaiwen
    Chen, Xi
    Gradient boosting decision tree in the prediction of NOx emission of waste incineration2023In: Energy, ISSN 0360-5442, E-ISSN 1873-6785, Vol. 264, article id 126174Article in journal (Refereed)
    Abstract [en]

    This paper investigates the real-time prediction of nitrogen oxides (NOx) emission by using around 17000 samples involved in a collection of three-day real data from a waste incineration power plant. To disclose the relationship between the ammonia (NH3) ejection and NOx emission, we choose the NOx reduction from inlet to outlet rather than the NOx concentration monitored by continuous emission monitoring system (CEMS). A hybrid procedure is developed to select appropriate features from the large and unsynchronized data, with which we establish a model based on the gradient boosting decision tree (GBDT) for the prediction. Computational experiments demonstrate that, with root mean square error (RMSE) values being 1.851 and 3.593 for training and test data, respectively, GBDT outperforms its two popular counterparts, supporting vector regression (SVR) and long short-term memory (LSTM). Shapley additive explanations (SHAP) is also conducted for analysis.

  • 33. Dong, Yihui
    et al.
    Wu, Na
    Ji, Xiaoyan
    Laaksonen, Aatto
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK). Nanjing Tech University, P. R. China; Luleå University of Technology, Sweden; Petru Poni Institute of Macromolecular Chemistry, Romania.
    Lu, Xiaohua
    Zhang, Suojiang
    Excellent Trace Detection of Proteins on TiO2 Nanotube Substrates through Novel Topography Optimization2020In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 124, no 50, p. 27790-27800Article in journal (Refereed)
    Abstract [en]

    For improving the surface-enhanced Raman scattering (SERS) performance of nanomaterials to achieve trace detection of proteins and complex biological systems, structural and topographical control is one of the important strategies. In this work, a facial and effective method to optimize the topography of TiO2 nanotube arrays (TNAs) is demonstrated, together with a significant enhancement of the SERS performance of cytochrome C (Cyt C) on TNAs. An enhancement factor (EF) up to 10(4), which is obtained with the newly developed method on the basis of the quantification of atomic force microscopy (AFM)-measured interaction force, is achieved, corresponding to a superior detection limit of Cyt C down to 10(-7) M. The main reason is that adjusting the fluoride contents in an electrolyte (from 0.4 to 0.1 wt %) can reduce the content and sizes of cracks, as well as the tube ruptures of TNAs, where the fluoride content at 0.2 wt % can successfully provide the excellent and optimized topography of TNAs. The TNAs with the optimized topography, especially those with larger tube diameters, demonstrated the importance of structural integrity on a remarkably excellent SERS performance in the trace detection of proteins. The proposed method will stimulate the development and optimization of the active substrate on the SERS applications in biology, bioanalysis, and nanoscience.

  • 34.
    Eriksson, Ann-Charlotte
    Stockholm University, Faculty of Social Sciences, Department of Psychology.
    Stresstoleransens vara eller icke vara: Bedömning av stresstolerans i en urvalsprocess2007Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [sv]

    Arbetslivet ställer allt högre krav på stresstolerans när kraven på flexibilitet ökar. Inom vissa yrkesområden har hög stresstolerans av naturliga skäl alltid varit ett grundläggande krav. Då stresstolerans förefaller mångfacetterat var syftet att göra en kvalitativ undersökning om hur professionella bedömare vid rekrytering och urval till yrken och yrkesutbildningar med höga krav på stresstolerans definierar och kartlägger denna egenskap samt vilka metoder de använder. Datainsamlingen genomfördes genom sju halvstrukturerade intervjuer med rekryterare samt psykologer knutna till försvarsmakten, flyg, brandförsvar, polis, räddningsverksamhet och kustbevakning. Resultatet som tolkades med induktiv tematisk analys, visar att detta genomförs med hjälp av typbestämning av stresstolerans, hypotesskapande testning, hypotesprövande helhetsbedömning samt kontroll av inre och yttre resurser. Slutsatsen är att stresstolerans betraktas både som en stabil och en situationsbunden egenskap och att bedömaren i huvudsak fungerar som instrument. Fler studier behövs genomföras, framför allt inom andra yrkesområden, för att säkerställa att stresstolerans inte bedöms enbart med fingertoppskänsla.

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  • 35. Fallah, Haniyeh
    et al.
    Lundberg, Peter
    Stockholm University, Faculty of Science, Department of Meteorology .
    Razvan, Mohammad Reza
    On the existence of canards in a nonlinear fluid system manifesting oscillatory behaviour2018In: International Journal of Non-Linear Mechanics, ISSN 0020-7462, E-ISSN 1878-5638, Vol. 98, p. 58-63Article in journal (Refereed)
    Abstract [en]

    In an earlier study dealing with a nonlinear fluid oscillator governed by two autonomous ODEs, the solutions were found to display some aberrant characteristics adjacent to the boundaries of the oscillatory regime in parameter space. It was argued that this behaviour indicated the presence of canards. In the present study it is formally proved that this indeed is the case, and some numerical examples illustrating the phenomenon as well as its effects are presented.

  • 36.
    Falowska-Pietrzak, Olga
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Bassler, Niels
    Hedqvist, Anders
    Stockholm University, Faculty of Science, Department of Physics.
    Hellberg, Fredrik
    Stockholm University, Faculty of Science, Department of Physics.
    Wolff-Fabris, Frederik
    Investigation of the stray radiation origin and composition at the European XFEL undulators with gafchromic films measurements and Geant4 simulations2023In: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, ISSN 0168-9002, E-ISSN 1872-9576, Vol. 1056, article id 168672Article in journal (Refereed)
    Abstract [en]

    At EuXFEL, a stray field of ionizing radiation is present near undulator magnets which eventually can lead to their demagnetization and decreased efficiency of the Self-Amplified Spontaneous Emission (SASE) process. In this work we investigate both the origin and composition of the radiation field at the undulator magnets with gafchromic film measurements and Geant4 Monte Carlo simulations. Both measurements and simulations suggest that the radiation field in the upstream undulator cells comes from high-energy electrons striking the beam pipe. In addition, horizontal dose distributions at the entrance of the undulator segments depend on where the electrons hit the beam pipe. Geant4 simulations show that the radiation fluence near magnets is dominated by photons, while charged secondary electrons and positrons contribute almost entirely to the ionizing dose absorbed by magnets.

  • 37.
    Fawzy Abdel-Magied, Ahmed
    Stockholm University, Faculty of Science, Department of Organic Chemistry. Nuclear Materials Authority, Egypt.
    Solid phase extraction of uranium from phosphoric acid: kinetic and thermodynamic study2017In: Radiochimica Acta, ISSN 0033-8230, E-ISSN 2193-3405, Vol. 105, no 10, p. 813-820Article in journal (Refereed)
    Abstract [en]

    There is a high interest to develop suitable solid phase extractants for uranium separation from aqueous solutions in order to reduce cost and enhance the efficiency. This paper describes solid phase extraction of uranium(VI) from aqueous phosphoric acid solution using MCM-41 based D2HEPA-TOPO organophosphorous extractants. The mixture of D2HEPA (di-2-ethyl-hexylphosphoric acid) and TOPO (tri-n-octylphosphine oxide) was impregnated into the pores of MCM-41 and the synthesized sorbent was fully characterized. The influences of different factors such as synergistic mixture ratio, phosphoric acid concentration, mixing time and temperature were investigated. The results showed that 90% of uranium(VI) extraction can be achieved within 5 min, using D2HEPATOPO@MCM-41 (mass ratio 2: 1 w/w) from 1 M phosphoric acid containing 64 ppm of uranium at room temperature. High adsorption capacity of uranium(VI) have been achieved at the mentioned conditions. The rate constant for the chemical adsorption of uranium(VI) was 0.988 g mg. 1 min. 1 calculated by the pseudo-second order rate equation. The obtained thermodynamics parameters showed that uranium(VI) adsorption from H-3 PO4 is an exothermic and spontaneous process.

  • 38. Fernández-Varea, José M.
    et al.
    Gonzalez-Muñoz, Gloria
    Galassi, Mariel E.
    Wiklund, Kristin
    Stockholm University, Faculty of Science, Medical Radiation Physics (together with KI).
    Lind, Bengt K.
    Stockholm University, Faculty of Science, Medical Radiation Physics (together with KI).
    Ahnesjö, Anders
    Tilly, Nina
    Limitations (and merits) of PENELOPE as a track-structure code2012In: International Journal of Radiation Biology, ISSN 0955-3002, E-ISSN 1362-3095, Vol. 88, no 1-2, p. 66-70Article in journal (Refereed)
    Abstract [en]

    Purpose: To outline the limitations of PENELOPE (acronym of PENetration and Energy LOss of Positrons and Electrons) as a track-structure code, and to comment on modifications that enable its fruitful use in certain microdosimetry and nanodosimetry applications.

    Methods: Attention is paid to the way in which inelastic collisions of electrons are modelled and to the ensuing implications for microdosimetry analysis.

    Results: Inelastic mean free paths and collision stopping powers calculated with PENELOPE and two well-known optical-data models are compared. An ad hoc modification of PENELOPE is summarized where ionization and excitation of liquid water by electron impact is simulated using tables of realistic differential and total cross sections.

    Conclusions: PENELOPE can be employed advantageously in some track-structure applications provided that the default model for inelastic interactions of electrons is replaced by suitable tables of differential and total cross sections.

  • 39.
    Fijoł, Natalia
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Aguilar-Sanchez, Andrea
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Mathew, Aji P.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    3D-printable biopolymer-based materials for water treatment: A review2022In: Chemical Engineering Journal, ISSN 1385-8947, E-ISSN 1873-3212, Vol. 430, article id 132964Article, review/survey (Refereed)
    Abstract [en]

    The global environmental concerns drive scientists all over the world to develop eco-friendly and sustainable alternatives to techniques and materials commonly used until now for water treatment applications. The relatively novel Additive manufacturing (AM) technology allows to process materials in a custom optimized, cost and time effective manner, while use of biobased materials minimizes the secondary pollution issue. Combining three-dimensional (3D) printing technology and biopolymer-based materials refines the water treatment industry, as it provides tailored water filtration systems easily available in the disadvantaged areas at low environmental impact and cost due to the raw materials' bio-origin and abundance. This review highlights the combination of various 3D printing techniques such as Fused deposition modelling (FDM), Direct ink wetting (DIW) and Stereolitography (SLA) with nature-derived biopolymers and biopolymerbased materials including chitosan, Polylactic acid (PLA), alginate and Cellulose acetate (CA) for their potential application within the water treatment industry with emphasis on oil separation and metal removal. Moreover, the environmental impact of the revised biopolymers is briefly discussed.

  • 40. Foda, O.
    et al.
    Zarembo, Konstantin
    Stockholm University, Nordic Institute for Theoretical Physics (Nordita). Uppsala University, Sweden.
    Overlaps of partial Neel states and Bethe states2016In: Journal of Statistical Mechanics: Theory and Experiment, E-ISSN 1742-5468, article id 023107Article in journal (Refereed)
    Abstract [en]

    Partial Neel states are generalizations of the ordinary Neel (classical anti-ferromagnet) state that can have arbitrary integer spin. We study overlaps of these states with Bethe states. We first identify this overlap with a partial version of reflecting-boundary domain-wall partition function, and then derive various determinant representations for off-shell and on-shell Bethe states.

  • 41. Francesc Barquinero, Joan
    et al.
    Beinke, Christina
    Borras, Mireia
    Buraczewska, Iwona
    Darroudi, Firouz
    Gregoire, Eric
    Hristova, Rositsa
    Kulka, Ulrike
    Lindholm, Carita
    Moreno, Mercedes
    Moquet, Jayne
    Oestreicher, Ursula
    Jesus Prieto, M.
    Pujol, Monica
    Ricoul, Michelle
    Sabatier, Laure
    Sommer, Sylwester
    Sun, Mingzhu
    Wojcik, Andrzej
    Stockholm University, Faculty of Science, Department of Molecular Biosciences, The Wenner-Gren Institute.
    Barrios, Leonardo
    RENEB biodosimetry intercomparison analyzing translocations by FISH2017In: International Journal of Radiation Biology, ISSN 0955-3002, E-ISSN 1362-3095, Vol. 93, no 1, p. 30-35Article in journal (Refereed)
    Abstract [en]

    Purpose: In the framework of RENEB, several biodosimetry exercises were conducted analyzing different endpoints. Among them, the analysis of translocations is considered the most useful method for retrospective biodosimetry due to the relative stability of their frequency with post irradiation time. The aim of this study was to harmonize the accuracy of translocation-based biodosimetry within the RENEB consortium. Materials and methods: An initial telescoring exercise analyzing FISH metaphase images was done to harmonize chromosome aberration descriptions. Then two blind intercomparison exercises (IE) were performed, by sending irradiated blood samples to each partner. Samples were cultured and stained by each partner using their standard protocol and translocation frequency was used to produce dose estimates. Results: The coefficient of variation in the 1st IE (CV = 0.34) was higher than in the 2nd IE (CV = 0.16 and 0.23 in the two samples analyzed), for the genomic frequency of total translocations. Z-score analysis revealed that eight out of 10 and 17 out of 20 dose estimates were satisfactory in the 1st and 2nd IE, respectively. Conclusions: The results obtained indicate that, despite the problems identified in few partners, which can be corrected, the RENEB consortium is able to carry out retrospective biodosimetry analyzing the frequency of translocations by FISH.

  • 42. Fries, J.
    et al.
    Sardina, G.
    Svensson, Gunilla
    Stockholm University, Faculty of Science, Department of Meteorology . Stockholm University, Faculty of Science, The Bolin Centre for Climate Research (together with KTH & SMHI).
    Pumir, A.
    Mehlig, B.
    Lagrangian Supersaturation Fluctuations at the Cloud Edge2023In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 131, no 25, article id 254201Article in journal (Refereed)
    Abstract [en]

    Evaporation of cloud droplets accelerates when turbulence mixes dry air into the cloud, affecting droplet-size distributions in atmospheric clouds, combustion sprays, and jets of exhaled droplets. The challenge is to model local correlations between droplet numbers, sizes, and supersaturation, which determine supersaturation fluctuations along droplet paths (Lagrangian fluctuations). We derived a statistical model that accounts for these correlations. Its predictions are in quantitative agreement with results of direct numerical simulations, and explain the key mechanisms at play.

  • 43. Gonzalez, Jose M.
    et al.
    Tomlinson, James E.
    Harou, Julien J.
    Martínez Ceseña, Eduardo A.
    Panteli, Mathaios
    Bottacin-Busolin, Andrea
    Hurford, Anthony
    Olivares, Marcelo A.
    Siddiqui, Afzal
    Stockholm University, Faculty of Social Sciences, Department of Computer and Systems Sciences. University College London, UK.
    Erfani, Tohid
    Strzepek, Kenneth M.
    Mancarella, Pierluigi
    Mutale, Joseph
    Obuobie, Emmanuel
    Seid, Abdulkarim H.
    Ya, Aung Ze
    Spatial and sectoral benefit distribution in water-energy system design2020In: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 269, article id 114794Article in journal (Refereed)
    Abstract [en]

    The design of water and energy systems has traditionally been done independently or considering simplified interdependencies between the two systems. This potentially misses valuable synergies between them and does not consider in detail the distribution of benefits between different sectors or regions. This paper presents a framework to couple integrated water-power network simulators with multi-objective optimisation under uncertainty to explore the implications of explicitly including spatial topology and interdependencies in the design of multi-sector integrated systems. A synthetic case study that incorporates sectoral dependencies in resource allocation, operation of multi-purpose reservoirs and spatially distributed infrastructure selection in both systems is used. The importance of explicitly modelling the distribution of benefits across different sectors and regions is explored by comparing different spatially aggregated and disaggregated multi-objective optimisation formulations. The results show the disaggregated formulation identifies a diverse set of non-dominated portfolios that enables addressing the spatial and sectoral distribution of benefits, whilst the aggregated formulations arbitrarily induce unintended biases. The proposed disaggregated approach allows for detailed spatial design of interlinked water and energy systems considering their complex regional and sectoral trade-offs. The framework is intended to assist planners in real resource systems where diverse stakeholder groups are mindful of receiving their fair share of development benefits.

  • 44. Gualtieri, P.
    et al.
    Picano, F.
    Sardina, Gaetano
    Stockholm University, Faculty of Science, Department of Meteorology .
    Casciola, C. M.
    Exact regularized point particle method for multiphase fows in the two-way coupling regime2015In: Journal of Fluid Mechanics, ISSN 0022-1120, E-ISSN 1469-7645, Vol. 773, p. 520-561Article in journal (Refereed)
    Abstract [en]

    Particulate flows have mainly been studied under the simplifying assumption of a one-way coupling regime where the disperse phase does not modify the carrier fluid. A more complete view of multiphase flows can be gained calling into play two-way coupling effects, i.e. by accounting for the inter-phase momentum exchange, which is certainly relevant at increasing mass loading. In this paper we present a new methodology rigorously designed to capture the inter-phase momentum exchange for particles smaller than the smallest hydrodynamical scale, e.g. the Kolmogorov scale in a turbulent flow. The momentum coupling mechanism exploits the unsteady Stokes flow around a small rigid sphere, where the transient disturbance produced by each particle is evaluated in a closed form. The particles are described as lumped point masses, which would lead to the appearance of singularities. A rigorous regularization procedure is conceived to extract the physically relevant interactions between the particles and the fluid which avoids any 'ad hoc' assumption. The approach is suited for high-efficiency implementation on massively parallel machines since the transient disturbance produced by the particles is strongly localized in space. We will show that hundreds of thousands of particles can be handled at an affordable computational cost, as demonstrated by a preliminary application to a particle-laden turbulent shear flow.

  • 45. Gumaelius, Lena
    et al.
    Norén, Agneta
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Voss, Mirjam
    Outreach initiatives operated by universities for increasing interest in science and technology2016In: European Journal of Engineering Education, ISSN 0304-3797, E-ISSN 1469-5898, Vol. 41, no 6, p. 589-622Article in journal (Refereed)
    Abstract [en]

    Since the 1990s, the low number of students choosing to study science and technology in higher education has been on the societal agenda and many initiatives have been launched to promote awareness regarding career options. The initiatives particularly focus on increasing enrolment in the engineering programmes. This article describes and compares eight European initiatives that have been established and operated by universities (and in some cases through collaboration with other actors in society). Each initiative is summarised in a short essay that discusses motivation, organisation, pedagogical approach, and activities. The initiatives are characterised by comparing the driving forces behind their creation, how the initiative activities relate to the activities at the university, size based on the number of participants and cost per participant and pedagogical framework. There seem to be two main tracks for building outreach activities, one where outreach activities are based on the university’s normal activities, and one where outreach activities are designed specifically for the visiting students. 

  • 46. Guo (郭佳诚), Jiacheng
    et al.
    Han (韩攀), Pan
    Zhang (张伟), Wei
    Wang (王君实), Junshi
    Lauder, George V.
    Di Santo, Valentina
    Stockholm University, Faculty of Science, Department of Zoology, Functional Morphology.
    Dong (董海波), Haibo
    Vortex dynamics and fin-fin interactions resulting in performance enhancement in fish-like propulsion2023In: Physical Review Fluids, E-ISSN 2469-990X, Vol. 8, no 7, article id 073101Article in journal (Refereed)
    Abstract [en]

    The leading-edge vortex (LEV) formation on the caudal fin (CF) has been identified as playing a key role in efficient lift-based thrust production of fish-like propulsion. The enhancement of the CF LEV through its interaction with vortices formed upstream due to a median fin with a distinct shape is the focus of this paper. High-speed, high-fidelity videos and particle imaging velocimetry (PIV) were obtained from rainbow trout during steady forward swimming to visualize the undulatory kinematics and two-dimensional flow behavior. Body kinematics are quantified using a traveling-wave formulation that is used to prescribe the motion of a high-fidelity three-dimensional surface model of the fish body for a computational fluid dynamics (CFD) study. The pressure field of the CFD result is compared and validated with the PIV result from the experiment. Using CFD, the vortex forming and shedding behaviors of the anal fin (AF) and their capturing and interaction with the trunk (TK) and the CF are visualized and examined. Coherent AF-bound LEVs are found to form periodically, leading to thrust production of the AF. The vortices subsequently shed from the AF are found to help stabilize and reinforce the LEV formation on the CF by aiding LEV initiation at stroke reversal and enhancing LEV during a tail stroke, which leads to enhancement of lift-based thrust production. The CF is found to shed vortex tubes (VTs) that create backward-facing jets, and the ventral-side VT and the associated backward jets are both strengthened by vortices shed by the AF. An additional benefit of the AF is found to be reduction of body drag by reducing the lateral crossflow that leads to loss of beneficial pressure gradient across the body. Through varying AF-CF spacing and AF height, we find that CF thrust enhancement and TK drag reduction due to the AF are both affected by the position and size of the AF. The position and area of the AF that led to the most hydrodynamic benefit are found to be the original, anatomically accurate position and size. In this paper, we demonstrate the important effect of vortex interaction among propulsive surfaces in fish-like propulsion.

  • 47.
    Hallengren, Anders
    Stockholm University, Faculty of Humanities, Department of Literature and History of Ideas.
    Fusionskraften snart verklighet1978In: Värld och vetande, ISSN 0346-4873, Vol. 27, no 4Article in journal (Other (popular science, discussion, etc.))
    Abstract [en]

    Ongoing experimental US and Soviet thermonuclear research envisioning future nuclear power plants based on fusion energy instead of nuclear fission and without radioactive waste. The crucial turning point occurs when energy supply exceeds energy consumption in these tests in high-energy physics.

  • 48.
    Hallengren, Anders
    Stockholm University, Faculty of Humanities, Department of Literature and History of Ideas.
    Stirlingmotorn – gårdagens framtidsmotor i morgon? Drivs med vad som helst, tyst och avgasren1980In: Värld och vetande, ISSN 0346-4873, Vol. 29, no 7, p. 193-202Article in journal (Refereed)
    Abstract [en]

    An overview and evaluation of the revival of the old Stirling engine in the days of nuclear phase-out and oil crisis. About the new attempts to replace the internal combustion engine with further developed heat engines—systems that convert heat to mechanical energy—with less efficiency and less effective power so far, but more environmental friendly and with a range of applications.

  • 49.
    Hao, Wenming
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Björkman, Eva
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Lilliestråle, Malte
    Hedin, Niklas
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Activated carbons prepared from hydrothermally carbonized waste biomass used as adsorbents for CO22013In: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 112, p. 526-532Article in journal (Refereed)
    Abstract [en]

    Activated carbons prepared from hydrothermally carbonized (HTC) waste biomass were studied with respect to the adsorption of carbon dioxide. The physically activated carbons (PAC) exhibited a large adsorption of CO2 of 1.45 mmol/g at a small partial pressure of CO2 (10 kPa and a temperature of 0 degrees C). These PACs were prepared by activation in a stream of CO2 and had significant amounts of ultramicropores, which were established by analyzing the adsorption of CO2 with a density functional theory. The uptake at such low pressures of CO2 is of most importance for an adsorption-driven CO2 capture from flue gas at large power stations, as it is difficult to imagine a pressurization of the flue gas. The capacities to adsorb CO2 of the different activated carbons were compared with both the micropore volumes as established by N-2 adsorption, and the ultramicropore volumes as established by CO2 adsorption. The ultramicropore volume is of crucial importance for the capture of CO2 from flue gas. PAC from HTC grass cuttings and from horse manure had the largest ultramicropore volumes. In general, the PAC showed excellent cyclability of adsorption/desorption of CO2 and a minimal capacity loss after subsequent cycles. In addition, the PAC showed a rapid adsorption of CO2. Both characteristics are essential for the eventual use of such PACs in the adsorption driven separation of CO2 from flue gas. A chemically activated carbon (CAC) was prepared by treating hydrothermally carbonized beer waste with H3PO4 and a heat treatment in a flow of N-2. This CAC showed a significant amount of mesopores in the range of 5 nm, in addition to micropores. The apparent selectivity for the activated carbons for CO2-over-N-2 adsorption was determined at 0 degrees C and 10 kPa.

  • 50.
    Haugen, Nils E. L.
    et al.
    Stockholm University, Nordic Institute for Theoretical Physics (Nordita). SINTEF Energi A.S., Norway; Luleå University of Technology, Sweden.
    Brandenburg, Axel
    Stockholm University, Nordic Institute for Theoretical Physics (Nordita). Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Sandin, Christer
    Stockholm University, Nordic Institute for Theoretical Physics (Nordita).
    Mattsson, Lars
    Stockholm University, Nordic Institute for Theoretical Physics (Nordita).
    Spectral characterisation of inertial particle clustering in turbulence2022In: Journal of Fluid Mechanics, ISSN 0022-1120, E-ISSN 1469-7645, Vol. 934, article id A37Article in journal (Refereed)
    Abstract [en]

    Clustering of inertial particles is important for many types of astrophysical and geophysical turbulence, but it has been studied predominately for incompressible flows. Here, we study compressible flows and compare clustering in both compressively (irrotationally) and vortically (solenoidally) forced turbulence. Vortically and compressively forced flows are driven stochastically either by solenoidal waves or by circular expansion waves, respectively. For compressively forced flows, the power spectrum of the density of inertial particles is a useful tool for displaying particle clustering relative to the fluid density enhancement. Power spectra are shown to be particularly sensitive for studying large-scale particle clustering, while conventional tools such as radial distribution functions are more suitable for studying small-scale clustering. Our primary finding is that particle clustering through shock interaction is particularly prominent in turbulence driven by spherical expansion waves. It manifests itself through a double-peaked distribution of spectral power as a function of Stokes number. The two peaks are associated with two distinct clustering mechanisms; shock interaction for smaller Stokes numbers and the centrifugal sling effect for larger values. The clustering of inertial particles is associated with the formation of caustics. Such caustics can only be captured in the Lagrangian description, which allows us to assess the relative importance of caustics in vortically and compressively forced turbulence. We show that the statistical noise resulting from the limited number of particles in the Lagrangian description can be removed from the particle power spectra, allowing us a more detailed comparison of the residual spectra. We focus on the Epstein drag law relevant for rarefied gases, but show that our findings apply also to the usual Stokes drag.

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