| 1. |
- Barack, Leor, et al.
(författare)
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Black holes, gravitational waves and fundamental physics : a roadmap
- 2019
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Ingår i: Classical and quantum gravity. - : IOP Publishing. - 0264-9381 .- 1361-6382. ; 36:14
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Forskningsöversikt (refereegranskat)abstract
- The grand challenges of contemporary fundamental physics dark matter, dark energy, vacuum energy, inflation and early universe cosmology, singularities and the hierarchy problem all involve gravity as a key component. And of all gravitational phenomena, black holes stand out in their elegant simplicity, while harbouring some of the most remarkable predictions of General Relativity: event horizons, singularities and ergoregions. The hitherto invisible landscape of the gravitational Universe is being unveiled before our eyes: the historical direct detection of gravitational waves by the LIGO-Virgo collaboration marks the dawn of a new era of scientific exploration. Gravitational-wave astronomy will allow us to test models of black hole formation, growth and evolution, as well as models of gravitational-wave generation and propagation. It will provide evidence for event horizons and ergoregions, test the theory of General Relativity itself, and may reveal the existence of new fundamental fields. The synthesis of these results has the potential to radically reshape our understanding of the cosmos and of the laws of Nature. The purpose of this work is to present a concise, yet comprehensive overview of the state of the art in the relevant fields of research, summarize important open problems, and lay out a roadmap for future progress. This write-up is an initiative taken within the framework of the European Action on 'Black holes, Gravitational waves and Fundamental Physics'.
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| 2. |
- Dzidic, Majda, et al.
(författare)
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Oral microbiota maturation during the first 7 years of life in relation to allergy development
- 2018
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Ingår i: Allergy. European Journal of Allergy and Clinical Immunology. - : WILEY. - 0105-4538 .- 1398-9995. ; 73:10, s. 2000-2011
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Tidskriftsartikel (refereegranskat)abstract
- Background Allergic diseases have become a major public health problem in affluent societies. Microbial colonization early in life seems to be critical for instructing regulation on immune system maturation and allergy development in children. Even though the oral cavity is the first site of encounter between a majority of foreign antigens and the immune system, the influence of oral bacteria on allergy development has not yet been reported. Objective Methods We sought to determine the bacterial composition in longitudinally collected saliva samples during childhood in relation to allergy development. Illumina sequencing of the 16S rDNA gene was used to characterize the oral bacterial composition in saliva samples collected at 3, 6, 12, 24 months, and 7 years of age from children developing allergic symptoms and sensitization (n = 47) and children staying healthy (n = 33) up to 7 years of age. Results Conclusion Children developing allergic disease, particularly asthma, had lower diversity of salivary bacteria together with highly divergent bacterial composition at 7 years of age, showing a clearly altered oral microbiota in these individuals, likely as a consequence of an impaired immune system during infancy. Moreover, the relative amounts of several bacterial species, including increased abundance of Gemella haemolysans in children developing allergies and Lactobacillus gasseri and L. crispatus in healthy children, were distinctive during early infancy, likely influencing early immune maturation. Early changes in oral microbial composition seem to influence immune maturation and allergy development. Future experiments should test the probiotic potential of L. gasseri and L. crispatus isolates.
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| 3. |
- Caldararu, Octav, et al.
(författare)
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Binding free energies in the SAMPL6 octa-acid host–guest challenge calculated with MM and QM methods
- 2018
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Ingår i: Journal of Computer-Aided Molecular Design. - : Springer Science and Business Media LLC. - 0920-654X .- 1573-4951. ; 32:10, s. 1027-1046
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Tidskriftsartikel (refereegranskat)abstract
- We have estimated free energies for the binding of eight carboxylate ligands to two variants of the octa-acid deep-cavity host in the SAMPL6 blind-test challenge (with or without endo methyl groups on the four upper-rim benzoate groups, OAM and OAH, respectively). We employed free-energy perturbation (FEP) for relative binding energies at the molecular mechanics (MM) and the combined quantum mechanical (QM) and MM (QM/MM) levels, the latter obtained with the reference-potential approach with QM/MM sampling for the MM → QM/MM FEP. The semiempirical QM method PM6-DH+ was employed for the ligand in the latter calculations. Moreover, binding free energies were also estimated from QM/MM optimised structures, combined with COSMO-RS estimates of the solvation energy and thermostatistical corrections from MM frequencies. They were performed at the PM6-DH+ level of theory with the full host and guest molecule in the QM system (and also four water molecules in the geometry optimisations) for 10–20 snapshots from molecular dynamics simulations of the complex. Finally, the structure with the lowest free energy was recalculated using the dispersion-corrected density-functional theory method TPSS-D3, for both the structure and the energy. The two FEP approaches gave similar results (PM6-DH+/MM slightly better for OAM), which were among the five submissions with the best performance in the challenge and gave the best results without any fit to data from the SAMPL5 challenge, with mean absolute deviations (MAD) of 2.4–5.2 kJ/mol and a correlation coefficient (R2) of 0.77–0.93. This is the first time QM/MM approaches give binding free energies that are competitive to those obtained with MM for the octa-acid host. The QM/MM-optimised structures gave somewhat worse performance (MAD = 3–8 kJ/mol and R2 = 0.1–0.9), but the results were improved compared to previous studies of this system with similar methods.
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| 4. |
- Engquist, Björn, et al.
(författare)
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Absorbing boundary conditions for the numerical simulation of waves
- 1997
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Ingår i: Mathematics of Computation. - 0025-5718 .- 1088-6842. ; 1, s. 629-651
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Tidskriftsartikel (refereegranskat)abstract
- In practical calculations, it is often essential to introduce artificial boundaries to limit the area of computation. Here we develop a systematic method for obtaining a hierarchy of local boundary conditions at these artifical boundaries. These boundary conditions not only guarantee stable difference approximations, but also minimize the (unphysical) artificial reflections that occur at the boundaries.
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| 5. |
- Engquist, Björn, et al.
(författare)
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Numerical radiation boundary conditions for unsteady transonic flow
- 1981
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Ingår i: Journal of Computational Physics. - : Elsevier BV. - 0021-9991 .- 1090-2716. ; 40:1, s. 91-103
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Tidskriftsartikel (refereegranskat)abstract
- A family of numerical boundary conditions for far-field-computational boundaries in calculations involving unsteady transonic flow is devised. These boundary conditions are developed in a systematic fashion from general principles. Both numerical and analytic comparisons with other currently used methods are given.
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| 6. |
- Engquist, Björn, et al.
(författare)
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Radiation boundary conditions for acoustic and elastic wave calculations
- 1979
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Ingår i: Communications on Pure and Applied Mathematics. - : Wiley. - 0010-3640 .- 1097-0312. ; 32:3, s. 314-358
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Tidskriftsartikel (refereegranskat)abstract
- A technique for developing radiating boundary conditions for artificial computational boundaries is described and applied to a class of problems typical in exploration seismology involving acoustic and elastic wave equations. First, one considers a constant coefficient scalar wave equation where the artificial boundary is one edge of a rectangular domain. By using continued fraction expansions, a systematic sequence of stable highly absorbing boundary conditions with successively better absorbing properties as the order of the boundary conditions increases is obtained. There follows a systematic derivation of a hierarchy of local radiating boundary conditions for the elastic wave equation. A theoretical procedure to guarantee stability at corners of the rectangular domain is worked out. A technique for fitting the discrete radiating boundary conditions directly to the difference scheme itself is proposed.
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| 7. |
- Engquist, Björn, et al.
(författare)
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Volumes in Mathematics and its Applications : Computational fluid dynamics and reacting gas flows
- 1988. - 12
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Bok (refereegranskat)abstract
- This volume contains papers presented at the workshop on Computational Fluid Dynamics and Reacting Gas Flows held at the Institute for Mathematics and Its Applications during September, 1986. Computational fluid dynamics has become a research area of central importance to mathematics, science, and technology. It is a subject which brings together applied mathematics and numerical analysis to solve problems in fluid dynamics. Included in this volume is the description of new algorithms which can make possible the discovery of important new scientific phenomena and the development of new technological processes. This volume will be of interest to mathematicians, scientists, and engineers who are interested in the current research of international leaders in numerical analysis and scientific computing
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