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  • 1. Agarwal, S.
    et al.
    Wettlaufer, J. S.
    KTH, Centra, Nordic Institute for Theoretical Physics NORDITA. Yale University, New Haven, CT, USA; Mathematical Institute, University of Oxford, Oxford, UK.
    Fluctuations in Arctic sea-ice extent: Comparing observations and climate models2018Ingår i: Philosophical Transactions. Series A: Mathematical, physical, and engineering science, ISSN 1364-503X, E-ISSN 1471-2962, Vol. 376, nr 2129, artikel-id 20170332Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The fluctuation statistics of the observed sea-ice extent during the satellite era are compared with model output from CMIP5 models using a multifractal time series method. The two robust features of the observations are that on annual to biannual time scales the ice extent exhibits white noise structure, and there is a decadal scale trend associated with the decay of the ice cover. It is shown that (i) there is a large inter-model variability in the time scales extracted from the models, (ii) none of the models exhibits the decadal time scales found in the satellite observations, (iii) five of the 21 models examined exhibit the observed white noise structure, and (iv) the multi-model ensemble mean exhibits neither the observed white noise structure nor the observed decadal trend. It is proposed that the observed fluctuation statistics produced by this method serve as an appropriate test bed for modelling studies. 

  • 2. Agarwal, Sahil
    et al.
    Wettlaufer, John S.
    Stockholms universitet, Nordiska institutet för teoretisk fysik (Nordita). Yale University, USA; University of Oxford, UK.
    Fluctuations in Arctic sea-ice extent: comparing observations and climate models2018Ingår i: Philosophical Transactions. Series A: Mathematical, physical, and engineering science, ISSN 1364-503X, E-ISSN 1471-2962, Vol. 376, nr 2129, artikel-id 20170332Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The fluctuation statistics of the observed sea-ice extent during the satellite era are compared with model output from CMIP5 models using a multifractal time series method. The two robust features of the observations are that on annual to biannual time scales the ice extent exhibits white noise structure, and there is a decadal scale trend associated with the decay of the ice cover. It is shown that (i) there is a large inter-model variability in the time scales extracted from the models, (ii) none of the models exhibits the decadal time scales found in the satellite observations, (iii) five of the 21 models examined exhibit the observed white noise structure, and (iv) the multi-model ensemble mean exhibits neither the observed white noise structure nor the observed decadal trend. It is proposed that the observed fluctuation statistics produced by this method serve as an appropriate test bed for modelling studies. This article is part of the theme issue 'Modelling of sea-ice phenomena'.

  • 3.
    Alfredsson, P. Henrik
    et al.
    KTH, Tidigare Institutioner (före 2005), Mekanik.
    Segalini, Antonio
    KTH, Skolan för teknikvetenskap (SCI), Centra, Linné Flow Center, FLOW.
    Wind farms in complex terrains: an introduction2017Ingår i: Philosophical Transactions. Series A: Mathematical, physical, and engineering science, ISSN 1364-503X, E-ISSN 1471-2962, Vol. 375, nr 2091Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Wind energy is one of the fastest growing sources of sustainable energy production. As more wind turbines are coming into operation, the best locations are already becoming occupied by turbines, and wind-farm developers have to look for new and still available areas-locations that may not be ideal such as complex terrain landscapes. In these locations, turbulence and wind shear are higher, and in general wind conditions are harder to predict. Also, the modelling of the wakes behind the turbines is more complicated, which makes energy-yield estimates more uncertain than under ideal conditions. This theme issue includes 10 research papers devoted to various fluid-mechanics aspects of using wind energy in complex terrains and illustrates recent progress and future developments in this important field. This article is part of the themed issue 'Wind energy in complex terrains'.

  • 4.
    Andersson, Lars-Erik
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Matematiska institutionen, Tillämpad matematik.
    Klarbring, Anders
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för konstruktions- och produktionsteknik, Mekanik.
    A review of the theory of static and quasi-static frictional contact problems in elasticity2001Ingår i: Philosophical Transactions. Series A: Mathematical, physical, and engineering science, ISSN 1364-503X, E-ISSN 1471-2962, Vol. 359, s. 2519-2539Artikel i tidskrift (Refereegranskat)
  • 5.
    Andersson, Ole
    et al.
    Dept. of Physics, Stockholm University, Sweden.
    Bengtsson, Ingemar
    Dept. of Physics, Stockholm University, Sweden.
    Ericsson, Marie
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för fysikalisk och analytisk kemi, Kvantkemi. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi.
    Sjöqvist, Erik
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi. Uppsala universitet.
    Geometric phases for mixed states of the Kitaev chain2016Ingår i: Philosophical Transactions. Series A: Mathematical, physical, and engineering science, ISSN 1364-503X, E-ISSN 1471-2962, Vol. 374, nr 2069, artikel-id 20150231Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The Berry phase has found applications in building topological order parameters for certain condensed matter systems. The question whether some geometric phase for mixed states can serve the same purpose has been raised, and proposals are on the table. We analyze the intricate behaviour of Uhlmann’s geometric phase in the Kitaev chain at finite temperature, and then argue that it captures quite different physics from that intended. We also analyze the behaviour of a geometric phase introduced in the context of interferometry. For the Kitaev chain, this phase closely mirrors that of the Berry phase, and we argue that it merits further investigation. 

  • 6.
    Andersson, Ole
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Bengtsson, Ingemar
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Ericsson, Marie
    Sjöqvist, Erik
    Geometric phases for mixed states of the Kitaev chain2016Ingår i: Philosophical Transactions. Series A: Mathematical, physical, and engineering science, ISSN 1364-503X, E-ISSN 1471-2962, Vol. 374, nr 2068, artikel-id 20150231Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The Berry phase has found applications in building topological order parameters for certain condensed matter systems. The question whether some geometric phase for mixed states can serve the same purpose has been raised, and proposals are on the table. We analyse the intricate behaviour of Uhlmann's geometric phase in the Kitaev chain at finite temperature, and then argue that it captures quite different physics from that intended. We also analyse the behaviour of a geometric phase introduced in the context of interferometry. For the Kitaev chain, this phase closely mirrors that of the Berry phase, and we argue that it merits further investigation.

  • 7.
    Asano, Masanari
    et al.
    Tokuyama College of Technology, Japan.
    Khrennikov, Andrei
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för matematik (MA).
    Ohya, Masanori
    Tokyo University of Science, Japan.
    Tanaka, Yoshiharu
    Tokyo University of Science, Japan.
    Yamato, Ichiro
    Tokyo University of Science, Japan.
    Three-body system metaphor for the two-slit experiment and Escherichia coli lactose-glucose metabolism2016Ingår i: Philosophical Transactions. Series A: Mathematical, physical, and engineering science, ISSN 1364-503X, E-ISSN 1471-2962, Vol. 374, nr 2068, artikel-id 20150243Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We compare the contextual probabilistic structures of the seminal two-slit experiment (quantum interference experiment), the system of three interacting bodies and Escherichia coli lactose-glucose metabolism. We show that they have the same non-Kolmogorov probabilistic structure resulting from multi-contextuality. There are plenty of statistical data with non-Kolmogorov features; in particular, the probabilistic behaviour of neither quantum nor biological systems can be described classically. Biological systems (even cells and proteins) are macroscopic systems and one may try to present a more detailed model of interactions in such systems that lead to quantum-like probabilistic behaviour. The system of interactions between three bodies is one of the simplest metaphoric examples for such interactions. By proceeding further in this way (by playing with n-body systems) we shall be able to find metaphoric mechanical models for complex bio-interactions, e.g. signalling between cells, leading to non-Kolmogorov probabilistic data.

  • 8.
    Bagarello, F.
    et al.
    Univ Palermo, Italy ; INFN, Italy.
    Haven, E.
    Univ Leicester, UK.
    Khrennikov, Andrei
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för matematik (MA). Natl Res Univ Informat Technol Mech & Opt ITMO, Russia.
    A model of adaptive decision-making from representation of information environment by quantum fields2017Ingår i: Philosophical Transactions. Series A: Mathematical, physical, and engineering science, ISSN 1364-503X, E-ISSN 1471-2962, Vol. 375, nr 2106, artikel-id 20170162Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We present the mathematical model of decisionmaking (DM) of agents acting in a complex and uncertain environment (combining huge variety of economical, financial, behavioural and geopolitical factors). To describe interaction of agents with it, we apply the formalism of quantum field theory (QTF). Quantum fields are a purely informational nature. The QFT model can be treated as a far relative of the expected utility theory, where the role of utility is played by adaptivity to an environment (bath). However, this sort of utility- adaptivity cannot be represented simply as a numerical function. The operator representation in Hilbert space is used and adaptivity is described as in quantum dynamics. We are especially interested in stabilization of solutions for sufficiently large time. The outputs of this stabilization process, probabilities for possible choices, are treated in the framework of classical DM. To connect classical and quantum DM, we appeal to Quantum Bayesianism. We demonstrate the quantumlike interference effect in DM, which is exhibited as a violation of the formula of total probability, and hence the classical Bayesian inference scheme. This article is part of the themed issue 'Second quantum revolution: foundational questions'.

  • 9.
    Bagheri, Shervin
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Mekanik, Stabilitet, Transition, Kontroll.
    Henningson, Dan S.
    KTH, Skolan för teknikvetenskap (SCI), Mekanik, Stabilitet, Transition, Kontroll.
    Transition delay using control theory2011Ingår i: Philosophical Transactions. Series A: Mathematical, physical, and engineering science, ISSN 1364-503X, E-ISSN 1471-2962, Vol. 369, nr 1940, s. 1365-1381Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This review gives an account of recent research efforts to use feedback control for the delay of laminar-turbulent transition in wall-bounded shear flows. The emphasis is on reducing the growth of small-amplitude disturbances in the boundary layer using numerical simulations and a linear control approach. Starting with the application of classical control theory to two-dimensional perturbations developing in spatially invariant flows, flow control based on control theory has progressed towards more realistic three-dimensional, spatially inhomogeneous flow configurations with localized sensing/actuation. The development of low-dimensional models of the Navier-Stokes equations has played a key role in this progress. Moreover, shortcomings and future challenges, as well as recent experimental advances in this multi-disciplinary field, are discussed.

  • 10. Bahaj, AbuBakr S.
    Marine current energy conversion: the dawn of a new era in electricity production2013Ingår i: Philosophical Transactions. Series A: Mathematical, physical, and engineering science, ISSN 1364-503X, E-ISSN 1471-2962Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Marine currents can carry large amounts of energy, largely driven by the tides, which are a consequence of the gravitational effects of the planetary motion of the Earth, the Moon and the Sun. Augmented flow velocities can be found where the underwater topography (bathymetry) in straits between islands and the mainland or in shallows around headlands plays a major role in enhancing the flow velocities, resulting in appreciable kinetic energy. At some of these sites where practical flows are more than 1 m s−1, marine current energy conversion is considered to be economically viable. This study describes the salient issues related to the exploitation of marine currents for electricity production, resource assessment, the conversion technologies and the status of leading projects in the field. This study also summarizes important issues related to site development and some of the approaches currently being undertaken to inform device and array development. This study concludes that, given the highlighted commitments to establish favourable regulatory and incentive regimes as well as the aspiration for energy independence and combating climate change, the progress to multi-megawatt arrays will be much faster than that achieved for wind energy development.

  • 11. Balmer, R. S.
    et al.
    Friel, I.
    Woollard, S. M.
    Wort, C. J. H.
    Scarsbrook, G. A.
    Coe, S. E.
    El-Hajj, H.
    Kaiser, A.
    Denisenko, A.
    Kohn, E.
    Isberg, Jan
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Unlocking diamond's potential as an electronic material2008Ingår i: Philosophical Transactions. Series A: Mathematical, physical, and engineering science, ISSN 1364-503X, E-ISSN 1471-2962, Vol. 366, nr 1863, s. 251-265Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this paper, we review the suitability of diamond as a semiconductor material for high-performance electronic applications. The current status of the manufacture of synthetic diamond is reviewed and assessed. In particular, we consider the quality of intrinsic material now available and the challenges in making doped structures suitable for practical devices. Two practical applications are considered in detail. First, the development of high-voltage switches capable of switching voltages in excess of 10kV. Second, the development of diamond MESFETs for high-frequency and high-power applications. Here device data are reported showing a current density of more than 30mAmm -1 along with small-signal RF measurements demonstrating gigahertz operation. We conclude by considering the remaining challenges which will need to be overcome if commercially attractive diamond electronic devices are to be manufactured.

  • 12. Batten, W.M.J.
    et al.
    Harrison, M.E.
    Bahaj, A. S.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    The accuracy of the actuator disc-RANS approach for predicting the performance and far wake of a horizontal axis tidal stream turbine2013Ingår i: Philosophical Transactions. Series A: Mathematical, physical, and engineering science, ISSN 1364-503X, E-ISSN 1471-2962Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The actuator disc-RANS model has been widely used in wind and tidal energy to predict the wake of a horizontal axis turbine. The model is appropriate where large scale effects of the turbine on a flow are of interest, for example, when considering environmental impacts, or arrays of devices. The accuracy of the model for modelling the wake of tidal stream turbines has not been demonstrated, and flow predictions presented in the literature for similar modelled scenarios vary significantly. This paper compares the results of the actuator disc-RANS model, where the turbine forces have been derived using a blade element approach, to experimental data measured in the wake of a scaled turbine. It also compares the results to those of a simpler uniform actuator disc model. The comparisons show that the model is accurate and can predict up to 94\% of the variation in the experimental data measured on the centreline of the wake. The study demonstrates that the actuator-disc RANS model is an accurate approach for modelling a turbine wake, and conservative approach to predict performance and loads. It can therfore applied to similar scenarios with confidence.

  • 13.
    Berggren, Karl-Fredrik
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Fysik. Linköpings universitet, Tekniska högskolan.
    Pepper, Michael
    University College London.
    Electrons in one dimension2010Ingår i: Philosophical Transactions. Series A: Mathematical, physical, and engineering science, ISSN 1364-503X, E-ISSN 1471-2962, Vol. 368, s. 1141-1162Artikel, forskningsöversikt (Refereegranskat)
    Abstract [en]

    In this article, we present a summary of the current status of the study of the transport of electrons confined to one dimension in very low disorder GaAs–AlGaAs heterostructures. By means of suitably located gates and application of a voltage to ‘electrostatically squeeze’ the electronic wave functions, it is possible to produce a controllable size quantization and a transition from two-dimensional transport. If the length of the electron channel is sufficiently short, then transport is ballistic and the quantized subbands each have a conductance equal to the fundamental quantum value 2e2/h, where the factor of 2 arises from the spin degeneracy. This mode of conduction is discussed, and it is shown that a number of many-body effects can be observed. These effects are discussed as in the spin-incoherent regime, which is entered when the separation of the electrons is increased and the exchange energy is less than kT. Finally, results are presented in the regime where the confinement potential is decreased and the electron configuration relaxes to minimize the electron–electron repulsion to move towards a two-dimensional array. It is shown that the ground state is no longer a line determined by the size quantization alone, but becomes two distinct rows arising from minimization of the electrostatic energy and is the precursor of a two-dimensional Wigner lattice.

  • 14. Betts, Richard A.
    et al.
    Alfieri, Lorenzo
    Bradshaw, Catherine
    Caesar, John
    Feyen, Luc
    Friedlingstein, Pierre
    Gohar, Laila
    Koutroulis, Aristeidis
    Lewis, Kirsty
    Morfopoulos, Catherine
    Papadimitriou, Lamprini
    Richardson, Katy J.
    Tsanis, Ioannis
    Wyser, Klaus
    SMHI, Forskningsavdelningen, Klimatforskning - Rossby Centre.
    Changes in climate extremes, fresh water availability and vulnerability to food insecurity projected at 1.5 degrees C and 2 degrees C global warming with a higher-resolution global climate model2018Ingår i: Philosophical Transactions. Series A: Mathematical, physical, and engineering science, ISSN 1364-503X, E-ISSN 1471-2962, Vol. 376, nr 2119, artikel-id 20160452Artikel i tidskrift (Refereegranskat)
  • 15.
    Blomqvist, Björn R. H.
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Matematiska institutionen, Tillämpad matematik och statistik.
    Sumpter, David J. T.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Matematiska institutionen, Tillämpad matematik och statistik.
    Mann, Richard P.
    Univ Leeds, Sch Math, Dept Stat, Leeds, W Yorkshire, England;Alan Turing Inst, London, England.
    Inferring the dynamics of rising radical right-wing party support using Gaussian processes2019Ingår i: Philosophical Transactions. Series A: Mathematical, physical, and engineering science, ISSN 1364-503X, E-ISSN 1471-2962, Vol. 377, nr 2160, artikel-id 20190145Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The use of classical regression techniques in social science can prevent the discovery of complex, nonlinear mechanisms and often relies too heavily on both the expertise and prior expectations of the data analyst. In this paper, we present a regression methodology that combines the interpretability of traditional, well used, statistical methods with the full predictability and flexibility of Bayesian statistics techniques. Our modelling approach allows us to find and explain the mechanisms behind the rise of Radical Right-wing Populist parties (RRPs) that we would have been unable to find using traditional methods. Using Swedish municipality-level data (2002-2018), we find no evidence that the proportion of foreign-born residents is predictive of increases in RRP support. Instead, education levels and population density are the significant variables that impact the change in support for the RRP, in addition to spatial and temporal control variables. We argue that our methodology, which produces models with considerably better fit of the complexity and nonlinearities often found in social systems, provides a better tool for hypothesis testing and exploration of theories about RRPs and other social movements. This article is part of the theme issue 'Coupling functions: dynamical interaction mechanisms in the physical, biological and social sciences'.

  • 16.
    Breton, Simon-Philippe
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper.
    Sumner, J.
    Dawson Coll, Dept Phys, Montreal, PQ, Canada..
    Sörensen, J. N.
    DTU Wind Energy, Lyngby, Denmark..
    Hansen, K. S.
    DTU Wind Energy, Lyngby, Denmark..
    Sarmast, S.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper.
    Ivanell, Stefan
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper.
    A survey of modelling methods for high-fidelity wind farm simulations using large eddy simulation2017Ingår i: Philosophical Transactions. Series A: Mathematical, physical, and engineering science, ISSN 1364-503X, E-ISSN 1471-2962, Vol. 375, nr 2091, artikel-id 20160097Artikel, forskningsöversikt (Refereegranskat)
    Abstract [en]

    Large eddy simulations (LES) of wind farms have the capability to provide valuable and detailed information about the dynamics of wind turbine wakes. For this reason, their use within the wind energy research community is on the rise, spurring the development of new models and methods. This review surveys the most common schemes available to model the rotor, atmospheric conditions and terrain effects within current state-of-the-art LES codes, of which an overview is provided. A summary of the experimental research data available for validation of LES codes within the context of single and multiple wake situations is also supplied. Some typical results for wind turbine and wind farm flows are presented to illustrate best practices for carrying out high-fidelity LES of wind farms under various atmospheric and terrain conditions. This article is part of the themed issue 'Wind energy in complex terrains'.

  • 17. Caffarelli, Luis A.
    et al.
    Shahgholian, Henrik
    KTH, Skolan för teknikvetenskap (SCI), Matematik (Inst.).
    Regularity of free boundaries a heuristic retro2015Ingår i: Philosophical Transactions. Series A: Mathematical, physical, and engineering science, ISSN 1364-503X, E-ISSN 1471-2962, Vol. 373, nr 2050, artikel-id 20150209Artikel, forskningsöversikt (Refereegranskat)
    Abstract [en]

    This survey concerns regularity theory of a few free boundary problems that have been developed in the past half a century. Our intention is to bring up different ideas and techniques that constitute the fundamentals of the theory. We shall discuss four different problems, where approaches are somewhat different in each case. Nevertheless, these problems can be divided into two groups: (i) obstacle and thin obstacle problem; (ii) minimal surfaces, and cavitation flow of a perfect fluid. In each case, we shall only discuss the methodology and approaches, giving basic ideas and tools that have been specifically designed and tailored for that particular problem. The survey is kept at a heuristic level with mainly geometric interpretation of the techniques and situations in hand.

  • 18. Chen, Gui-Qiang
    et al.
    Shahgholian, Henrik
    KTH, Skolan för teknikvetenskap (SCI), Matematik (Inst.).
    Vazquez, Juan-Luis
    Free boundary problems: the forefront of current and future developments2015Ingår i: Philosophical Transactions. Series A: Mathematical, physical, and engineering science, ISSN 1364-503X, E-ISSN 1471-2962, Vol. 373, nr 2050, artikel-id 20140285Artikel i tidskrift (Övrigt vetenskapligt)
  • 19. Cho, Daeheum
    et al.
    Rouxel, Jérémy R.
    Kowalewski, Markus
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Lee, Jin Yong
    Mukamel, Shaul
    Imaging of transition charge densities involving carbon core excitations by all X-ray sum-frequency generation2019Ingår i: Philosophical Transactions. Series A: Mathematical, physical, and engineering science, ISSN 1364-503X, E-ISSN 1471-2962, Vol. 377, nr 2145, artikel-id 2017.0470Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    X-ray diffraction signals from the time-evolving molecular charge density induced by selective core excitation of chemically inequivalent carbon atoms are calculated. A narrowband X-ray pulse selectively excites the carbon K-edge of the –CH3 or –CH2F groups in fluoroethane (CH3–CH2F). Each excitation creates a distinct core coherence which depends on the character of the electronic transition. Direct propagation of the reduced single-electron density matrix, using real-time time-dependent density functional theory, provides the time-evolving charge density following interactions with external fields. The interplay between partially filled valence molecular orbitals upon core excitation induces characteristic femtosecond charge migration which depends on the core–valence coherence, and is monitored by the sum-frequency generation diffraction signal.

  • 20. Christensen, T. R
    et al.
    Johansson, T
    Olsrud, M
    Ström, L
    Lindroth, A
    Mastepanov, M
    Malmer, N
    Friborg, T
    Crill, P
    Callaghan, T. V
    A catchment-scale carbon and greenhouse gas budget of a subarctic landscape2007Ingår i: Philosophical Transactions. Series A: Mathematical, physical, and engineering science, ISSN 1364-503X, E-ISSN 1471-2962, Vol. 365, nr 1856, s. 1643-1656Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This is the first attempt to budget average current annual carbon (C) and associated greenhouse gas (GHG) exchanges and transfers in a subarctic landscape, the Lake Torneträsk catchment in northern Sweden. This is a heterogeneous area consisting of almost 4000 km2 of mixed heath, birch and pine forest, and mires, lakes and alpine ecosystems. The magnitudes of atmospheric exchange of carbon in the form of the GHGs, CO2 and CH4 in these various ecosystems differ significantly, ranging from little or no flux in barren ecosystems over a small CO2 sink function and low rates of CH4 exchange in the heaths to significant CO2 uptake in the forests and also large emissions of CH4 from the mires and small lakes. The overall catchment budget, given the size distribution of the individual ecosystem types and a first approximation of run-off as dissolved organic carbon, reveals a landscape currently with a significant sink capacity for atmospheric CO2. This sink capacity is, however, extremely sensitive to environmental changes, particularly those that affect the birch forest ecosystem. Climatic drying or wetting and episodic events such as insect outbreaks may cause significant changes in the sink function. Changes in the sources of CH4 through increased permafrost melting may also easily change the sign of the current radiative forcing, due to the stronger impact per gram of CH4 relative to CO2. Hence, to access impacts on climate, the atmospheric C balance alone has to be weighed in a radiative forcing perspective. When considering the emissions of CH4 from the mires and lakes as CO2 equivalents, the Torneträsk catchment is currently a smaller sink of radiative forcing, but it can still be estimated as representing the equivalent of approximately 14 000 average Swedish inhabitants’ emissions of CO2. This can be compared with the carbon emissions of less than 200 people who live permanently in the catchment, although this comparison disregards substantial emissions from the non-Swedish tourism and transportation activities.

  • 21.
    Coates, C. S.
    et al.
    Inorgan Chem Lab, South Parks Rd, Oxford OX1 3QR, England.
    Gray, H. J.
    Inorgan Chem Lab, South Parks Rd, Oxford OX1 3QR, England.
    Bulled, J. M.
    Inorgan Chem Lab, South Parks Rd, Oxford OX1 3QR, England.
    Boström, Hanna
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Oorganisk kemi.
    Simonov, A.
    Inorgan Chem Lab, South Parks Rd, Oxford OX1 3QR, England.
    Goodwin, A. L.
    Inorgan Chem Lab, South Parks Rd, Oxford OX1 3QR, England.
    Ferroic multipolar order and disorder in cyanoelpasolite molecular perovskites2019Ingår i: Philosophical Transactions. Series A: Mathematical, physical, and engineering science, ISSN 1364-503X, E-ISSN 1471-2962, Vol. 377, nr 2149, artikel-id 20180219Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We use a combination of variable-temperature highresolution synchrotron X-ray powder diffraction measurements and Monte Carlo simulations to characterize the evolution of two different types of ferroic multipolar order in a series of cyanoelpasolite molecular perovskites. We show that ferroquadrupolar order in [C3N2H5](2)Rb[Co(CN)(6)] is a first-order process that is well described by a fourstate Potts model on the simple cubic lattice. Likewise, ferrooctupolar order in [NMe4](2)B[Co(CN)(6)] (B= K, Rb, Cs) also emerges via a first-order transition that now corresponds to a six-state Potts model. Hence, for these particular cases, the dominant symmetry breaking mechanisms are well understood in terms of simple statistical mechanical models. By varying composition, we find that the effective coupling between multipolar degrees of freedom- and hence the temperature at which ferromultipolar order emerges-can be tuned in a chemically sensible manner. This article is part of the theme issue 'Mineralomimesis: natural and synthetic frameworks in science and technology'.

  • 22. Curia, S.
    et al.
    Barclay, A. F.
    Torron, Susana
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Johansson, Mats
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Howdle, S. M.
    Green process for green materials: viable low-temperature lipase-catalysed synthesis of renewable telechelics in supercritical CO22015Ingår i: Philosophical Transactions. Series A: Mathematical, physical, and engineering science, ISSN 1364-503X, E-ISSN 1471-2962, Vol. 373, nr 2057, artikel-id 20150073Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We present a novel near-ambient-temperature approach to telechelic renewable polyesters by exploiting the unique properties of supercritical CO2 (scCO(2)). Bio-based commercially available monomers have been polymerized and functional telechelic materials with targeted molecular weight prepared by end-capping the chains with molecules containing reactive moieties in a one-pot reaction. The use of scCO(2) as a reaction medium facilitates the effective use of Candida antarctica Lipase B (CaLB) as a catalyst at a temperature as low as 35 degrees C, hence avoiding side reactions, maintaining the end-capper functionality and preserving the enzyme activity. The functionalized polymer products have been characterized by H-1 nuclear magnetic resonance spectroscopy, matrix-assisted laser desorption/ionization-time-of-flight mass spectrometry, gel permeation chromatography and differential scanning calorimetry in order to carefully assess their structural and thermal properties. We demonstrate that telechelic materials can be produced enzymatically at mild temperatures, in a solvent-free system and using renewably sourced monomers without pre-modification, by exploiting the unique properties of scCO(2). The macromolecules we prepare are ideal green precursors that can be further reacted to prepare useful bio-derived films and coatings.

  • 23. Daly, T.
    et al.
    Myers, L. E.
    Bahaj, A. S.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Modelling of the flow field surrounding tidal turbine arrays for varying positions in a channel2013Ingår i: Philosophical Transactions. Series A: Mathematical, physical, and engineering science, ISSN 1364-503X, E-ISSN 1471-2962Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The modelling of tidal turbines and the hydrodynamic effects of tidal power extraction represents a relatively new challenge in the field of computational fluid dynamics. Many different methods of defining flow and boundary conditions have been postulated and examined to determine how accurately they replicate the many parameters associated with tidal power extraction. This paper outlines the results of numerical modelling analysis carried out to investigate different methods of defining the inflow velocity boundary condition. This work is part of a wider research programme investigating flow effects in tidal turbine arrays. Results of this numerical analysis were benchmarked against previous experimental work conducted at the University of Southampton Chilworth hydraulics laboratory. Results show significant differences between certain methods of defining inflow velocities. However, certain methods do show good correlation with experimental results. This correlation would appear to justify the use of these velocity inflow definition methods in future numerical modelling of the far-field flow effects of tidal turbine arrays.

  • 24. Dandouras, Iannis
    et al.
    Garnier, Philippe
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutet för rymdfysik, Uppsalaavdelningen.
    Mitchell, Donald G.
    Roelof, Edmond C.
    Brandt, Pontus C.
    Krupp, Norbert
    Krimigis, Stamatios M.
    Titan's exosphere and its interaction with Saturn's magnetosphere2009Ingår i: Philosophical Transactions. Series A: Mathematical, physical, and engineering science, ISSN 1364-503X, E-ISSN 1471-2962, Vol. 367, nr 1889, s. 743-752Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Titan's nitrogen-rich atmosphere is directly bombarded by energetic ions, due to its lack of a significant intrinsic magnetic field. Singly charged energetic ions from Saturn's magnetosphere undergo charge-exchange collisions with neutral atoms in Titan's upper atmosphere, or exosphere, being transformed into energetic neutral atoms (ENAs). The ion and neutral camera, one of the three sensors that comprise the magnetosphere imaging instrument (MIMI) on the Cassini/Huygens mission to Saturn and Titan, images these ENAs like photons, and measures their fluxes and energies. These remote-sensing measurements, combined with the in situ measurements performed in the upper thermosphere and in the exosphere by the ion and neutral mass spectrometer instrument, provide a powerful diagnostic of Titan's exosphere and its interaction with the Kronian magnetosphere. These observations are analysed and some of the exospheric features they reveal are modelled.

  • 25.
    D'Ariano, Giacomo Mauro
    et al.
    Univ Pavia, Italy.
    Khrennikov, Andrei
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för matematik (MA).
    Preface of the special issue quantum foundations: information approach2016Ingår i: Philosophical Transactions. Series A: Mathematical, physical, and engineering science, ISSN 1364-503X, E-ISSN 1471-2962, Vol. 374, nr 2068, artikel-id 20150244Artikel i tidskrift (Övrigt vetenskapligt)
    Abstract [en]

    This special issue is based on the contributions of a group of top experts in quantum foundations and quantum information and probability. It enlightens a number of interpretational, mathematical and experimental problems of quantum theory.

  • 26. Delvenne, Jean-Charles
    et al.
    Sandberg, Henrik
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Dissipative open systems theory as a foundation for the thermodynamics of linear systems2017Ingår i: Philosophical Transactions. Series A: Mathematical, physical, and engineering science, ISSN 1364-503X, E-ISSN 1471-2962, Vol. 375, nr 2088, artikel-id 20160218Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this paper, we advocate the use of open dynamical systems, i.e. systems sharing input and output variables with their environment, and the dissipativity theory initiated by Jan Willems as models of thermodynamical systems, at the microscopic and macroscopic level alike. We take linear systems as a study case, where we show how to derive a global Lyapunov function to analyse networks of interconnected systems. We define a suitable notion of dynamic non-equilibrium temperature that allows us to derive a discrete Fourier law ruling the exchange of heat between lumped, discrete-space systems, enriched with the Maxwell-Cattaneo correction. We complete these results by a brief recall of the steps that allow complete derivation of the dissipation and fluctuation in macroscopic systems (i.e. at the level of probability distributions) from lossless and deterministic systems. This article is part of the themed issue 'Horizons of cybernetical physics'.

  • 27. Ehrenfreund, Pascale
    et al.
    Spaans, Marco
    Holm, Nils G.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för geologiska vetenskaper.
    The evolution of organic matter in space2011Ingår i: Philosophical Transactions. Series A: Mathematical, physical, and engineering science, ISSN 1364-503X, E-ISSN 1471-2962, Vol. 369, nr 1936, s. 538-554Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Carbon, and molecules made from it, have already been observed in the early Universe. During cosmic time, many galaxies undergo intense periods of star formation, during which heavy elements like carbon, oxygen, nitrogen, silicon and iron are produced. Also, many complex molecules, from carbon monoxide to polycyclic aromatic hydrocarbons, are detected in these systems, like they are for our own Galaxy. Interstellar molecular clouds and circumstellar envelopes are factories of complex molecular synthesis. A surprisingly high number of molecules that are used in contemporary biochemistry on the Earth are found in the interstellar medium, planetary atmospheres and surfaces, comets, asteroids and meteorites and interplanetary dust particles. Large quantities of extra-terrestrial material were delivered via comets and asteroids to young planetary surfaces during the heavy bombardment phase. Monitoring the formation and evolution of organic matter in space is crucial in order to determine the prebiotic reservoirs available to the early Earth. It is equally important to reveal abiotic routes to prebiotic molecules in the Earth environments. Materials from both carbon sources (extra-terrestrial and endogenous) may have contributed to biochemical pathways on the Earth leading to life’s origin. The research avenues discussed also guide us to extend our knowledge to other habitable worlds.

  • 28. Figalli, Alessio
    et al.
    Shahgholian, Henrik
    KTH, Skolan för teknikvetenskap (SCI), Matematik (Inst.).
    An overview of unconstrained free boundary problems2015Ingår i: Philosophical Transactions. Series A: Mathematical, physical, and engineering science, ISSN 1364-503X, E-ISSN 1471-2962, Vol. 373, nr 2050, artikel-id 20140281Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this paper, we present a survey concerning unconstrained free boundary problems of type F-1(D(2)u, del u, u, x) = 0 in B-1 boolean AND Omega, F-2(D(2)u, del u, u, x) = 0 in B-1 \ Omega, u is an element of S(B-1), where B-1 is the unit ball, Omega is an unknown open set, F-1 and F-2 are elliptic operators (admitting regular solutions), and S is a functions space to be specified in each case. Our main objective is to discuss a unifying approach to the optimal regularity of solutions to the above matching problems, and list several open problems in this direction.

  • 29. Geyer, Anna
    et al.
    Quirchmayr, Ronald
    Shallow water equations for equatorial tsunami waves2018Ingår i: Philosophical Transactions. Series A: Mathematical, physical, and engineering science, ISSN 1364-503X, E-ISSN 1471-2962, Vol. 376, nr 2111, artikel-id 20170100Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We present derivations of shallow water model equations of Korteweg-de Vries and Boussinesq type for equatorial tsunami waves in the f-plane approximation and discuss their applicability. This article is part of the theme issue 'Nonlinear water waves'.

  • 30.
    Grandfield, Kathryn
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Tillämpad materialvetenskap.
    Palmquist, Anders
    Engqvist, Håkan
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Tillämpad materialvetenskap.
    High-resolution three-dimensional probes of biomaterials and their interfaces2012Ingår i: Philosophical Transactions. Series A: Mathematical, physical, and engineering science, ISSN 1364-503X, E-ISSN 1471-2962, Vol. 370, nr 1963, s. 1337-1351Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Interfacial relationships between biomaterials and tissues strongly influence the success of implant materials and their long-term functionality. Owing to the inhomogeneity of biological tissues at an interface, in particular bone tissue, two-dimensional images often lack detail on the interfacial morphological complexity. Furthermore, the increasing use of nanotechnology in the design and production of biomaterials demands characterization techniques on a similar length scale. Electron tomography (ET) can meet these challenges by enabling high-resolution three-dimensional imaging of biomaterial interfaces. In this article, we review the fundamentals of ET and highlight its recent applications in probing the three-dimensional structure of bioceramics and their interfaces, with particular focus on the hydroxyapatite-bone interface, titanium dioxide-bone interface and a mesoporous titania coating for controlled drug release.

  • 31.
    Gunawidjaja, Philips N.
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK), Avdelningen för fysikalisk kemi.
    Mathew, Renny
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK), Avdelningen för fysikalisk kemi.
    Lo, Andy Y. H.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK), Avdelningen för fysikalisk kemi.
    Izquierdo-Barba, Isabel
    Garcia, Ana
    Arcos, Daniel
    Vallet-Regi, Maria
    Eden, Mattias
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK), Avdelningen för fysikalisk kemi.
    Local structures of mesoporous bioactive glasses and their surface alterations in vitro: inferences from solid-state nuclear magnetic resonance2012Ingår i: Philosophical Transactions. Series A: Mathematical, physical, and engineering science, ISSN 1364-503X, E-ISSN 1471-2962, Vol. 370, nr 1963, s. 1376-1399Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We review the benefits of using Si-29 and H-1 magic angle spinning (MAS) nuclear magnetic resonance (NMR) spectroscopy for probing the local structures of both bulk and surface portions of mesoporous bioactive glasses (MBGs) of the CaO-SiO2-(P2O5) system. These mesoporous materials exhibit an ordered pore arrangement, and are promising candidates for improved bone and tooth implants. We discuss experimental MAS NMR results from three MBGs displaying different Ca, Si and P contents: the Si-29 NMR spectra were recorded either directly by employing radio-frequency pulses to Si-29, or by magnetization transfers from neighbouring protons using cross polarization, thereby providing quantitative information about the silicate speciation present in the pore wall and at the MBG surface, respectively. The surface modifications were monitored for the three MBGs during their immersion in a simulated body fluid (SBF) for intervals between 30 min and one week. The results were formulated as a reaction sequence describing the interconversions between the distinct silicate species. We generally observed a depletion of Ca2+ ions at the MBG surface, and a minor condensation of the silicate-surface network over one week of SBF soaking.

  • 32.
    Gustafsson, Björn
    KTH, Skolan för teknikvetenskap (SCI), Matematik (Inst.).
    Vortex motion and geometric function theory: the role of connections2019Ingår i: Philosophical Transactions. Series A: Mathematical, physical, and engineering science, ISSN 1364-503X, E-ISSN 1471-2962, Vol. 377, nr 2158, artikel-id 20180341Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We formulate the equations for point vortex dynamics on a closed two-dimensional Riemannian manifold in the language of affine and other kinds of connections. This can be viewed as a relaxation of standard approaches, using the Riemannian metric directly, to an approach based more on local coordinates provided with a minimal amount of extra structure. The speed of a vortex is then expressed in terms of the difference between an affine connection derived from the coordinate Robin function and the Levi-Civita connection associated with the Riemannian metric. A Hamiltonian formulation of the same dynamics is also given. The relevant Hamiltonian function consists of two main terms. One of the terms is the well-known quadratic form based on a matrix whose entries are Green and Robin functions, while the other term describes the energy contribution from those circulating flows which are not implicit in the Green functions. One main issue of the paper is a detailed analysis of the somewhat intricate exchanges of energy between these two terms of the Hamiltonian. This analysis confirms the mentioned dynamical equations formulated in terms of connections. This article is part of the theme issue 'Topological and geometrical aspects ofmass and vortex dynamics'.

  • 33.
    Göransson, Peter
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg.
    Acoustic and vibrational damping in porous solids2006Ingår i: Philosophical Transactions. Series A: Mathematical, physical, and engineering science, ISSN 1364-503X, E-ISSN 1471-2962, Vol. 364, nr 1838, s. 89-108Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A porous solid may be characterized as an elastic-viscoelastic and acoustic-viscoacoustic medium. For a flexible, open cell porous foam, the transport of energy is carried both through the sound pressure waves propagating through the fluid in the pores, and through the elastic stress waves carried through the solid frame of the material. For a given situation, the balance between energy dissipated through vibration of the solid frame, changes in the acoustic pressure and the coupling between the waves varies with the topological arrangement, choice of material properties, interfacial conditions, etc. Engineering of foams, i.e. designs built on systematic and continuous relationships between polymer chemistry, processing, micro-structure, is still a vision for the future. However, using state-of-the-art simulation techniques, multiple layer arrangements of foams may be tuned to provide acoustic and vibrational damping at a low-weight penalty. In this paper, Biot's modelling of porous foams is briefly reviewed from an acoustics and vibrations perspective with a focus on the energy dissipation mechanisms. Engineered foams will be discussed in terms of results from simulations performed using finite element solutions. A layered vehicle-type structure is used as an example.

  • 34. Haggmark, C. P.
    et al.
    Bakchinov, A. A.
    Alfredsson, P. Henrik
    KTH, Tidigare Institutioner                               , Mekanik.
    Experiments on a two-dimensional laminar separation bubble2000Ingår i: Philosophical Transactions. Series A: Mathematical, physical, and engineering science, ISSN 1364-503X, E-ISSN 1471-2962, Vol. 358, nr 1777, s. 3193-3205Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A two-dimensional separation bubble on a flat plate is studied experimentally by means of hot-wire anemometry and flow visualization. Separation of the laminar boundary layer on the plate is caused by an adverse pressure gradient imposed by a curved wall opposite to the plate. The instability of, and transition process in, the separation bubble are focused on. The bubble is found to be highly susceptible to high-frequency two-dimensional instability waves, which are studied under both natural and forced conditions. A similar development of these instability waves in the separation bubble is found in both cases. The exponential growth of the two-dimensional disturbances dominates the flow except for in the reattachment region, where large-scale three-dimensional structures appear. Some difficulties associated with experimental investigations of boundary-layer separation-bubble flows are discussed.

  • 35.
    Haven, Emmanuel
    et al.
    Univ Leicester, UK.
    Khrennikov, Andrei
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för matematik (MA).
    Quantum probability and the mathematical modelling of decision-making2016Ingår i: Philosophical Transactions. Series A: Mathematical, physical, and engineering science, ISSN 1364-503X, E-ISSN 1471-2962, Vol. 374, nr 2058, artikel-id 20150105Artikel i tidskrift (Övrigt vetenskapligt)
  • 36.
    Hilchenbach, Martin
    et al.
    Max-Planck-Institut, Germany.
    Fischer, Henning
    Max-Planck-Institut, Germany.
    Langevin, Yves
    CNRS Université Paris Sud, France.
    Merouane, Sihane
    Max-Planck-Institut, Germany.
    Paquette, John
    Max-Planck-Institut, Germany.
    Rynö, Jouni
    Finnish Meteorological Institute, Finland.
    Stenzel, Oliver
    Max-Planck-Institut, Germany.
    Briois, Christelle
    CNRS Université d'Orléans, France.
    Kissel, Jochen
    Max-Planck-Institut, Germany.
    Koch, Andreas
    von Hoerner und Sulger GmbH, Germany.
    Schulz, Rita
    ESA-ESTEC, The Netherlands.
    Silen, Johan
    Finnish Meteorological Institute, Finland.
    Altobelli, Nicolas
    ESA-ESAC, Spain.
    Baklouti, Donia
    CNRS Université Paris Sud, France.
    Bardyn, Anais
    CNRS Université d'Orléans, France; CNRS Université Paris Est Créteil et Université Paris Diderot, France.
    Cottin, Herve
    CNRS Université d'Orléans, France.
    Engrand, Cecile
    CNRS Université d'Orléans, France.
    Fray, Nicolas
    CNRS Université Paris Est Créteil et Université Paris Diderot, France.
    Haerendel, Gerhard
    Max-Planck-Institut, Germany.
    Henkel, Hartmut
    CNRS Université d'Orléance, France.
    Höfner, Herwig
    Max-Planck-Institut, Germany.
    Hornung, Klaus
    Universität der Bundeswehr LRT-7, Germany.
    Lehto, Harry
    University of Turku, Finland.
    Mellado, Eva M.
    University of Turku, Finland.
    Modica, Paola
    CNRS Université d'Orléans, France; CNRS Université Paris Est Créteil et Université Paris Diderot, France.
    Le Roy, Lena
    University of Bern, Switzerland.
    Siljeström, Sandra
    RISE - Research Institutes of Sweden, Biovetenskap och material, Kemi och material.
    Steiger, Wolfgang
    RC Seibersdorf Research GmbH Business Field Aerospace Technology, Austria.
    Thirkell, Laurent
    CNRS Université d'Orléans, France.
    Thomas, Roger
    Finnish Meteorological Institute, Finland.
    Torkar, Klaus
    Austrian Academy of Sciences, Austria.
    Varmuza, Kurt
    Vienna University of Technology, Austria.
    Zaprudin, Boris
    RC Seibersdorf Research GmbH Business Field Aerospace Technology, Austria.
    Mechanical and electrostatic experiments with dust particles collected in the inner coma of comet 67P by COSIMA onboard Rosetta2017Ingår i: Philosophical Transactions. Series A: Mathematical, physical, and engineering science, ISSN 1364-503X, E-ISSN 1471-2962, Vol. 375, nr 2097Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The in situ cometary dust particle instrument COSIMA (COmetary Secondary Ion Mass Analyser) onboard ESA's Rosetta mission has collected about 31 000 dust particles in the inner coma of comet 67P/Churyumov-Gerasimenko since August 2014. The particles are identified by optical microscope imaging and analysed by time-of-flight secondary ion mass spectrometry. After dust particle collection by low speed impact on metal targets, the collected particle morphology points towards four families of cometary dust particles. COSIMA is an in situ laboratory that operates remotely controlled next to the comet nucleus. The particles can be further manipulated within the instrument by mechanical and electrostatic means after their collection by impact. The particles are stored above 0°C in the instrument and the experiments are carried out on the refractory, ice-free matter of the captured cometary dust particles. An interesting particle morphology class, the compact particles, is not fragmented on impact. One of these particles was mechanically pressed and thereby crushed into large fragments. The particles are good electrical insulators and transform into rubble pile agglomerates by the application of an energetic indium ion beam during the secondary ion mass spectrometry analysis. This article is part of the themed issue 'Cometary science after Rosetta'. © 2017 The Authors.

  • 37.
    Holmqvist, Cecilia
    et al.
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för fysik och elektroteknik (IFE).
    Belzig, Wolfgang
    Fogelström, Mikael
    Non-equilibrium charge and spin transport in superconducting–ferromagnetic–superconducting point contacts2018Ingår i: Philosophical Transactions. Series A: Mathematical, physical, and engineering science, ISSN 1364-503X, E-ISSN 1471-2962, Vol. 376, nr 2125, artikel-id 20150229Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The conventional Josephson effect may be modified by introducing spin-active scattering in the interface layer of the junction. Here, we discuss a Josephson junction consisting of two s-wave superconducting leads coupled over a classical spin that precesses with the Larmor frequency due to an external magnetic field. This magnetically active interface results in a time-dependent boundary condition with different tunnelling amplitudes for spin-up and -down quasi- particles and where the precession produces spin-flip scattering processes. As a result, the Andreev states develop sidebands and a non-equilibrium population that depend on the details of the spin precession. The Andreev states carry a steady-state Josephson charge current and a time-dependent spin current, whose current–phase relations could be used to characterize the precessing spin. The spin current is supported by spin-triplet correlations induced by the spin precession and creates a feedback effect on the classical spin in the form of a torque that shifts the precession frequency. By applying a bias voltage, the Josephson frequency adds another complexity to the situation and may create resonances together with the Larmor frequency. These Shapiro resonances manifest as torques and, under suitable 2conditions, are able to reverse the direction of the classical spin in sub-nanosecond time. Another characteristic feature is the subharmonic gap structure in the DC charge current displaying an even–odd effect attributable to precession-assisted multiple Andreev reflections. This article is part of the theme issue ‘Andreev bound states’.

  • 38.
    Holzapfel, Gerhard A.
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Hållfasthetslära (Inst.), Biomekanik.
    Ogden, R. W.
    Constitutive modelling of passive myocardium: a structurally based framework for material characterization2009Ingår i: Philosophical Transactions. Series A: Mathematical, physical, and engineering science, ISSN 1364-503X, E-ISSN 1471-2962, Vol. 367, nr 1902, s. 3445-3475Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this paper, we first of all review the morphology and structure of the myocardium and discuss the main features of the mechanical response of passive myocardium tissue, which is an orthotropic material. Locally within the architecture of the myocardium three mutually orthogonal directions can be identified, forming planes with distinct material responses. We treat the left ventricular myocardium as a non-homogeneous, thick-walled, nonlinearly elastic and incompressible material and develop a general theoretical framework based on invariants associated with the three directions. Within this framework we review existing constitutive models and then develop a structurally based model that accounts for the muscle fibre direction and the myocyte sheet structure. The model is applied to simple shear and biaxial deformations and a specific form fitted to the existing (and somewhat limited) experimental data, emphasizing the orthotropy and the limitations of biaxial tests. The need for additional data is highlighted. A brief discussion of issues of convexity of the model and related matters concludes the paper.

  • 39.
    Hovmöller, Sven
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Zou, Linus Hovmöller
    Zou, Xiaodong
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Grushko, Benjamin
    Structures of pseudo-decagonal approximants in Al-Co-Ni2012Ingår i: Philosophical Transactions. Series A: Mathematical, physical, and engineering science, ISSN 1364-503X, E-ISSN 1471-2962, Vol. 370, nr 1969, s. 2949-2959Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Quasi-crystals shocked the crystallographic world when they were reported in 1984. We now know that they are not a rare exception, and can be found in many alloy systems. One of the richer systems for quasi-crystals and their approximants is Al-Co-Ni. A large series of pseudo-decagonal (PD) approximants have been found. Only two of them, PD4 and PD8, have been solved by X-ray crystallography. We report here the structures of PD1, PD2, PD3 and PD5, solved from the limited information that is provided by electron diffraction patterns, unit cell dimensions and high-resolution electron microscopy images.

  • 40.
    Höök, Mikael
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Globala energisystem.
    Davidsson, Simon
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Globala energisystem.
    Johansson, Sheshti
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Globala energisystem.
    Tang, Xu
    China University of Petroleum - Beijing.
    Decline and depletion rates of oil production: a comprehensive investigation2014Ingår i: Philosophical Transactions. Series A: Mathematical, physical, and engineering science, ISSN 1364-503X, E-ISSN 1471-2962, Vol. 372, nr 2006, s. 0120448-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Two of the most fundamental concepts in the current debate about future oil supply are oil field decline rates and depletion rates. These concepts are related, but not identical. This paper clarifies the definitions of these concepts, summarises the underlying theory and empirically estimates decline and depletion rates for different categories of oil field. A database of 880 post-peak fields is analysed to determine typical depletion levels, depletion rates, and decline rates. This demonstrates that the size of oil fields has a significant influence on decline and depletion rates, with generally high values for small fields and comparatively low values for larger fields. These empirical findings have important implications for oil supply forecasting.

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  • 41.
    Höök, Mikael
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Globala energisystem.
    Fantazzini, Dean
    Moscow School of Economics.
    Angelantoni, André
    Post Peak Living.
    Snowden, Simon
    Liverpool University.
    Hydrocarbon liquefaction: viability as a peak oil mitigation strategy2014Ingår i: Philosophical Transactions. Series A: Mathematical, physical, and engineering science, ISSN 1364-503X, E-ISSN 1471-2962, Vol. 372, nr 2006, s. 20120319-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Current world capacity of hydrocarbon liquefaction is around 400,000 barrels per day (kb/d), providing a marginal share of the global liquid fuel supply. This study performs a broad review of technical, economic, environmental, and supply chains issues related to coal-to-liquids (CTL) and gas-to-liquids (GTL). We find three issues predominate. First, significant amounts of coal and gas would be required to obtain anything more than a marginal production of liquids. Second, the economics of CTL plants are clearly prohibitive, but are better for GTL. Nevertheless, large scale GTL plants still require very high upfront costs, and for three real world GTL plants out of four, the final cost has been so far approximately three times that initially budgeted. Small scale GTL holds potential for associated gas. Third, CTL and GTL both incur significant environmental impacts, ranging from increased greenhouse gas emissions (in the case of CTL) to water contamination. Environmental concerns may significantly affect growth of these projects until adequate solutions are found.

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  • 42.
    Jaeger, Gregg
    et al.
    Boston Univ, USA.
    Khrennikov, Andrei
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för matematik (MA).
    Perinotti, Paolo
    Univ Pavia, Italy.
    Preface for the special issue, 'Second quantum revolution: foundational questions'2017Ingår i: Philosophical Transactions. Series A: Mathematical, physical, and engineering science, ISSN 1364-503X, E-ISSN 1471-2962, Vol. 375, nr 2106, artikel-id 20160397Artikel i tidskrift (Övrigt vetenskapligt)
  • 43. John, E. H.
    et al.
    Pearson, P. N.
    Coxall, H.elen K.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för geologiska vetenskaper.
    Birch, H.
    Wade, B.S.
    Foster, G. L.
    Warm ocean processes and carbon cycling in the Eocene2013Ingår i: Philosophical Transactions. Series A: Mathematical, physical, and engineering science, ISSN 1364-503X, E-ISSN 1471-2962, Vol. 371, nr 2001, s. 1-21Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Sea surface and subsurface temperatures over large parts of the ocean during the Eocene epoch (55.5-33.7 Ma) exceeded modern values by several degrees, which must have affected a number of oceanic processes. Here, we focus on the effect of elevated water column temperatures on the efficiency of the biological pump, particularly in relation to carbon and nutrient cycling. We use stable isotope values from exceptionally well-preserved planktonic foraminiferal calcite from Tanzania and Mexico to reconstruct vertical carbon isotope gradients in the upper water column, exploiting the fact that individual species lived and calcified at different depths. The oxygen isotope ratios of different species' tests are used to estimate the temperature of calcification, which we converted to absolute depths using Eocene temperature profiles generated by general circulation models. This approach, along with potential pitfalls, is illustrated using data from modern core-top assemblages from the same area. Our results indicate that, during the Early and Middle Eocene, carbon isotope gradients were steeper (and larger) through the upper thermocline than in the modern ocean. This is consistent with a shallower average depth of organic matter remineralization and supports previously proposed hypotheses that invoke high metabolic rates in a warm Eocene ocean, leading to more efficient recycling of organic matter and reduced burial rates of organic carbon.

  • 44.
    Jonsell, Svante
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Collisions involving antiprotons and antihydrogen: an overview2018Ingår i: Philosophical Transactions. Series A: Mathematical, physical, and engineering science, ISSN 1364-503X, E-ISSN 1471-2962, Vol. 376, nr 2116, artikel-id 20170271Artikel, forskningsöversikt (Refereegranskat)
    Abstract [en]

    I give an overview of experimental and theoretical results for antiproton and antihydrogen scattering with atoms and molecules (in particular H, He). At low energies (less than or similar to 1 keV) there are practically no experimental data available. Instead I compare the results from different theoretical calculations, of various degrees of sophistication. At energies up to a few tens of eV, I focus on simple approximations that give reasonably accurate results, as these allow quick estimates of collision rates without embarking on a research project. This article is part of the Theo Murphy meeting issue 'Antiproton physics in the ELENA era'.

  • 45.
    Kacar, Betul
    et al.
    Harvard University, Cambridge, USA.
    Guy, Lionel
    Uppsala universitet, Medicinska och farmaceutiska vetenskapsområdet, Medicinska fakulteten, Institutionen för medicinsk biokemi och mikrobiologi.
    Smith, Eric
    Earth-Science Life Institute, Tokyo, Japan; Santa Fe Institute, SantaFe, USA.
    Baross, John
    University of Washington, Seattle, USA.
    Resurrecting ancestral genes in bacteria to interpret ancient biosignatures2017Ingår i: Philosophical Transactions. Series A: Mathematical, physical, and engineering science, ISSN 1364-503X, E-ISSN 1471-2962, Vol. 375, nr 2109, artikel-id 20160352Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Two datasets, the geologic record and the genetic content of extant organisms, provide complementary insights into the history of how key molecular components have shaped or driven global environmental and macroevolutionary trends. Changes in global physico-chemical modes over time are thought to be a consistent feature of this relationship between Earth and life, as life is thought to have been optimizing protein functions for the entirety of its approximately 3.8 billion years of history on the Earth. Organismal survival depends on how well critical genetic and metabolic components can adapt to their environments, reflecting an ability to optimize efficiently to changing conditions. The geologic record provides an array of biologically independent indicators of macroscale atmospheric and oceanic composition, but provides little in the way of the exact behaviour of the molecular components that influenced the compositions of these reservoirs. By reconstructing sequences of proteins that might have been present in ancient organisms, we can downselect to a subset of possible sequences that may have been optimized to these ancient environmental conditions. How can one use modern life to reconstruct ancestral behaviours? Configurations of ancient sequences can be inferred from the diversity of extant sequences, and then resurrected in the laboratory to ascertain their biochemical attributes. One way to augment sequence-based, single-gene methods to obtain a richer and more reliable picture of the deep past, is to resurrect inferred ancestral protein sequences in living organisms, where their phenotypes can be exposed in a complex molecular-systems context, and then to link consequences of those phenotypes to biosignatures that were preserved in the independent historical repository of the geological record. As a first step beyond single-molecule reconstruction to the study of functional molecular systems, we present here the ancestral sequence reconstruction of the beta-carbonic anhydrase protein. We assess how carbonic anhydrase proteins meet our selection criteria for reconstructing ancient biosignatures in the laboratory, which we term palaeophenotype reconstruction.This article is part of the themed issue 'Reconceptualizing the origins of life'.

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  • 46.
    Karlsson, J Stefan
    et al.
    Umeå universitet, Medicinska fakulteten, Institutionen för strålningsvetenskaper, Radiofysik.
    Roeleveld, Karin
    Grönlund, Christer
    Umeå universitet, Medicinska fakulteten, Institutionen för strålningsvetenskaper, Radiofysik.
    Holtermann, Andreas
    Östlund, Nils
    Umeå universitet, Medicinska fakulteten, Institutionen för strålningsvetenskaper, Radiofysik.
    Signal processing of the surface electromyogram to gain insight into neuromuscular physiology.2009Ingår i: Philosophical Transactions. Series A: Mathematical, physical, and engineering science, ISSN 1364-503X, E-ISSN 1471-2962, Vol. 367, nr 1887, s. 337-356Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A surface electromyogram (sEMG) contains information about physiological and morphological characteristics of the active muscle and its neural strategies. Because the electrodes are situated on the skin above the muscle, the sEMG is an easily obtainable source of information. However, different combinations of physiological and morphological characteristics can lead to similar sEMG signals and sEMG recordings contain noise and other artefacts. Therefore, many sEMG signal processing methods have been developed and applied to allow insight into neuromuscular physiology. This paper gives an overview of important advances in the development and applications of sEMG signal processing methods, including spectral estimation, higher order statistics and spatio-temporal processing. These methods provide information about muscle activation dynamics and muscle fatigue, as well as characteristics and control of single motor units (conduction velocity, firing rate, amplitude distribution and synchronization).

  • 47.
    Khrennikov, Andrei
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för matematik (MA).
    Quantum Bayesianism as the basis of general theory of decision-making2016Ingår i: Philosophical Transactions. Series A: Mathematical, physical, and engineering science, ISSN 1364-503X, E-ISSN 1471-2962, Vol. 374, nr 2068, artikel-id 20150245Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We discuss the subjective probability interpretation of the quantum-like approach to decision making and more generally to cognition. Our aim is to adopt the subjective probability interpretation of quantum mechanics, quantum Bayesianism (QBism), to serve quantum-like modelling and applications of quantum probability outside of physics. We analyse the classical and quantum probabilistic schemes of probability update, learning and decision-making and emphasize the role of Jeffrey conditioning and its quantum generalizations. Classically, this type of conditioning and corresponding probability update is based on the formula of total probability-one the basic laws of classical probability theory.

  • 48.
    Khrennikov, Andrei
    Linnéuniversitetet, Fakulteten för teknik (FTK), Institutionen för matematik (MA).
    'Social Laser': action amplification by stimulated emission of social energy2016Ingår i: Philosophical Transactions. Series A: Mathematical, physical, and engineering science, ISSN 1364-503X, E-ISSN 1471-2962, Vol. 374, nr 2058, artikel-id 20150094Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The problem of the 'explanation' of recent social explosions, especially in the Middle East, but also in Southern Europe and the USA, has been debated actively in the social and political literature. We can mention the contributions of P. Mason, F. Fukuyama, E. Schmidt, J. Cohen and I. Krastev to this debate. We point out that the diversity of opinions and conclusions is really amazing. At the moment, there is no consistent and commonly acceptable theory of these phenomena. We present a model of social explosions based on a novel approach for the description of social processes, namely the quantum-like approach. Here quantum theory is treated simply as an operational formalism-without any direct relation to physics. We explore the quantum-like laser model to describe the possibility of action amplification by stimulated emission of social energy.

  • 49.
    Koopmans, Bert
    et al.
    Eindhoven University of Technology, Netherlands; Eindhoven University of Technology, Netherlands.
    Wagemans, Wiebe
    Eindhoven University of Technology, Netherlands; Eindhoven University of Technology, Netherlands.
    Bloom, Francisco L.
    Eindhoven University of Technology, Netherlands; Eindhoven University of Technology, Netherlands.
    Bobbert, Peter A.
    Eindhoven University of Technology, Netherlands; Eindhoven University of Technology, Netherlands.
    Kemerink, Martijn
    Eindhoven University of Technology, Netherlands; Eindhoven University of Technology, Netherlands.
    Wohlgenannt, Markus
    University of Iowa, IA 52242 USA; University of Iowa, IA 52242 USA.
    Spin in organics: a new route to spintronics2011Ingår i: Philosophical Transactions. Series A: Mathematical, physical, and engineering science, ISSN 1364-503X, E-ISSN 1471-2962, Vol. 369, nr 1951, s. 3602-3616Artikel, forskningsöversikt (Refereegranskat)
    Abstract [en]

    New developments in the nascent field of organic spintronics are discussed. Two classes of phenomena can be discerned. In hybrid organic spin valves (OSVs), an organic semiconducting film is sandwiched between two ferromagnetic (FM) thin films, aiming at magnetoresistive effects as a function of the relative alignment of the respective magnetization directions. Alternatively, organic magnetoresistance (OMAR) is achieved without any FM components, and is an intrinsic property of the organic semiconductor material. Some of the exciting characteristics of OMAR, in both electrical conductance and photoconductance, are presented. A systematic, combined experimental-theoretical study of sign changes between positive and negative magnetoresistance is shown to provide important insight about the underlying mechanisms of OMAR. A simple explanation of experimental observations is obtained by combining a spin-blocking mechanism, an essential ingredient in the recently proposed bipolaron model, with specific features of the device physics of space charge limited current devices in the bipolar regime. Finally, we discuss possible links between the physics relevant for OMAR and that for OSVs. More specifically, weak hyperfine fields from the hydrogen atoms in organic materials are thought to be crucial for a proper understanding of both types of phenomena.

  • 50. Koven, C. D.
    et al.
    Schuur, E. A. G.
    Schaedel, C.
    Bohn, T. J.
    Burke, E. J.
    Chen, G.
    Chen, X.
    Ciais, P.
    Grosse, G.
    Harden, J. W.
    Hayes, D. J.
    Hugelius, Gustaf
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi.
    Jafarov, E. E.
    Krinner, G.
    Kuhry, Peter
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi.
    Lawrence, D. M.
    MacDougall, A. H.
    Marchenko, S. S.
    McGuire, A. D.
    Natali, S. M.
    Nicolsky, D. J.
    Olefeldt, D.
    Peng, S.
    Romanovsky, V. E.
    Schaefer, K. M.
    Strauss, J.
    Treat, C. C.
    Turetsky, M.
    A simplified, data-constrained approach to estimate the permafrost carbon-climate feedback2015Ingår i: Philosophical Transactions. Series A: Mathematical, physical, and engineering science, ISSN 1364-503X, E-ISSN 1471-2962, Vol. 373, nr 2054, artikel-id 20140423Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We present an approach to estimate the feedback from large-scale thawing of permafrost soils using a simplified, data-constrained model that combines three elements: soil carbon (C) maps and profiles to identify the distribution and type of C in permafrost soils; incubation experiments to quantify the rates of C lost after thaw; and models of soil thermal dynamics in response to climate warming. We call the approach the Permafrost Carbon Network Incubation-Panarctic Thermal scaling approach (PInc-PanTher). The approach assumes that C stocks do not decompose at all when frozen, but once thawed follow set decomposition trajectories as a function of soil temperature. The trajectories are determined according to a three-pool decomposition model fitted to incubation data using parameters specific to soil horizon types. We calculate litterfall C inputs required to maintain steady-state C balance for the current climate, and hold those inputs constant. Soil temperatures are taken from the soil thermal modules of ecosystem model simulations forced by a common set of future climate change anomalies under two warming scenarios over the period 2010 to 2100. Under a medium warming scenario (RCP4.5), the approach projects permafrost soil C losses of 12.2-33.4 Pg C; under a high warming scenario (RCP8.5), the approach projects C losses of 27.9-112.6 Pg C. Projected C losses are roughly linearly proportional to global temperature changes across the two scenarios. These results indicate a global sensitivity of frozen soil C to climate change (gamma sensitivity) of -14 to -19 PgC degrees C-1 on a 100 year time scale. For CH4 emissions, our approach assumes a fixed saturated area and that increases in CH4 emissions are related to increased heterotrophic respiration in anoxic soil, yielding CH4 emission increases of 7% and 35% for the RCP4.5 and RCP8.5 scenarios, respectively, which add an additional greenhouse gas forcing of approximately 10-18%. The simplified approach presented here neglects many important processes that may amplify or mitigate C release from permafrost soils, but serves as a data-constrained estimate on the forced, large-scale permafrost C response to warming.

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