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| 2. |
- Andersson, Theresa, et al.
(author)
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The binding of human Carbonic Anhydrase II by functionalized folded polypeptide receptors
- 2005
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In: Chemistry and Biology. - : Elsevier BV. - 1074-5521 .- 1879-1301. ; 12:11, s. 1245-1252
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Journal article (peer-reviewed)abstract
- Several receptors for human carbonic anhydrase II (HCAII) have been prepared by covalently attaching benzenesulfonamide carboxylates via aliphatic aminocarboxylic acid spacers of variable length to the side chain of a lysine residue in a designed 42 residue helix-loop-helix motif. The sulfonamide group binds to the active site zinc ion of human carbonic anhydrase II located in a 15 Å deep cleft. The dissociation constants of the receptor-HCAII complexes were found to be in the range from low micromolar to better than 20 nM, with the lowest affinities found for spacers with less than five methylene groups and the highest affinity found for the spacer with seven methylene groups. The results suggest that the binding is a cooperative event in which both the sulfonamide residue and the helix-loop-helix motif contribute to the overall affinity.
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| 3. |
- Berg, Marcus, 1973-, et al.
(author)
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Growth Histories in Bimetric Massive Gravity
- 2012
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In: Journal of Cosmology and Astroparticle Physics. - Bristol : Institute of Physics (IOP). - 1475-7516. ; :12
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Journal article (peer-reviewed)abstract
- We perform cosmological perturbation theory in Hassan-Rosen bimetric gravity for general homogeneous and isotropic backgrounds. In the de Sitter approximation, we obtain decoupled sets of massless and massive scalar gravitational fluctuations. Matter perturbations then evolve like in Einstein gravity. We perturb the future de Sitter regime by the ratio of matter to dark energy, producing quasi-de Sitter space. In this more general setting the massive and massless fluctuations mix. We argue that in the quasi-de Sitter regime, the growth of structure in bimetric gravity differs from that of Einstein gravity.
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| 4. |
- Blomqvist, Michael, et al.
(author)
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Constraining dark energy fluctuations with supernova correlations
- 2010
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In: Journal of Cosmology and Astroparticle Physics. - : IOP Publishing. - 1475-7516. ; 10, s. 018-
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Journal article (peer-reviewed)abstract
- We investigate constraints on dark energy fluctuations using type Ia supernovae. If dark energy is not in the form of a cosmological constant, that is if the equation of state is not equal to -1, we expect not only temporal, but also spatial variations in the energy density. Such fluctuations would cause local variations in the universal expansion rate and directional dependences in the redshift-distance relation. We present a scheme for relating a power spectrum of dark energy fluctuations to an angular covariance function of standard candle magnitude fluctuations. The predictions for a phenomenological model of dark energy fluctuations are compared to observational data in the form of the measured angular covariance of Hubble diagram magnitude residuals for type Ia supernovae in the Union2 compilation. The observational result is consistent with zero dark energy fluctuations. However, due to the limitations in statistics, current data still allow for quite general dark energy fluctuations as long as they are in the linear regime.
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| 5. |
- Bull, Philip, et al.
(author)
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Beyond ΛCDM : Problems, solutions, and the road ahead
- 2016
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In: Physics of the Dark Universe. - : Elsevier BV. - 2212-6864. ; 12, s. 56-99
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Journal article (peer-reviewed)abstract
- Despite its continued observational successes, there is a persistent (and growing) interest in extending cosmology beyond the standard model, Lambda CDM. This is motivated by a range of apparently serious theoretical issues, involving such questions as the cosmological constant problem, the particle nature of dark matter, the validity of general relativity on large scales, the existence of anomalies in the CMB and on small scales, and the predictivity and testability of the inflationary paradigm. In this paper, we summarize the current status of Lambda CDM as a physical theory, and review investigations into possible alternatives along a number of different lines, with a particular focus on highlighting the most promising directions. While the fundamental problems are proving reluctant to yield, the study of alternative cosmologies has led to considerable progress, with much more to come if hopes about forthcoming high-precision observations and new theoretical ideas are fulfilled.
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| 6. |
- Enander, Jonas, et al.
(author)
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Cosmic expansion histories in massive bigravity with symmetric matter coupling
- 2015
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In: Journal of Cosmology and Astroparticle Physics. - : IOP Publishing. - 1475-7516. ; :1
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Journal article (peer-reviewed)abstract
- We study the cosmic expansion history of massive bigravity with a viable matter coupling which treats both metrics on equal footing. We derive the Friedmann equation for the effective metric through which matter couples to the two metrics, and study its solutions. For certain parameter choices, the background cosmology is identical to that of LCDM. More general parameters yield dynamical dark energy, which can still be in agreement with observations of the expansion history. We study specific parameter choices of interest, including minimal models, maximally-symmetric models, and a candidate partially-massless theory.
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| 7. |
- Enander, Jonas, 1981-
(author)
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Cosmic tests of massive gravity
- 2015
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Doctoral thesis (other academic/artistic)abstract
- Massive gravity is an extension of general relativity where the graviton, which mediates gravitational interactions, has a non-vanishing mass. The first steps towards formulating a theory of massive gravity were made by Fierz and Pauli in 1939, but it took another 70 years until a consistent theory of massive gravity was written down. This thesis investigates the phenomenological implications of this theory, when applied to cosmology. In particular, we look at cosmic expansion histories, structure formation, integrated Sachs-Wolfe effect and weak lensing, and put constraints on the allowed parameter range of the theory. This is done by using data from supernovae, the cosmic microwave background, baryonic acoustic oscillations, galaxy and quasar maps and galactic lensing.The theory is shown to yield both cosmic expansion histories, galactic lensing and an integrated Sachs-Wolfe effect consistent with observations. For the structure formation, however, we show that for certain parameters of the theory there exists a tension between consistency relations for the background and stability properties of the perturbations. We also show that a background expansion equivalent to that of general relativity does not necessarily mean that the perturbations have to evolve in the same way.
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| 8. |
- Enander, Jonas
(author)
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Information Processing in the Nervous System. On a Holistic Functional Organization Principle.
- 2019
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Doctoral thesis (other academic/artistic)abstract
- This thesis is concerned with the nature of information processing in the nervous system. This issue has been investigated with animal experiments, using male Sprague–Dawley rats, and simulated touch generated by an artificial fingertip with neuromorphic tactile sensors. The processing of the tactile input from the artificial touch system has been analyzed in light of two opposing theories on information integration in the nervous system. The commonly accepted theory of functional localization, where distinct functions are believed to reside in localized clusters of neurons (e.g. the specific digit area of the primary somatosensory cortex); and the opposing holistic theory where function is seen as a result of the net activity of the nervous system, i.e. as an integrated whole. In addition to the experimental studies, a simulation study has been made to evaluate the validity of a selforganizational formative principle for the connectivity schemes seen in the spinal cord. Self-organization is a cornerstone for the holistic theory and hence the inclusion. The above outline has resulted in four papers. In paper I a dense interaction between the neocortical representations of individual digits was shown, questioning the discrete nature of historically popular cortical maps. In paper II this was further expanded when complex responses to tactile stimuli was found across the whole dorsal surface of the neocortex. The interdependence between these findings were implicated in paper III in which we showed that a stroke in a distant cortical area had a negative impact on the decoding performance of tactile stimuli in the primary somatosensory cortex, thus serving as support for the holistic theory of an indivisible neocortical modus operandi. Finally, in paper IV an initial argument was made for self-organization rather than detailed preprogramming as the formative rule for circuit formation. Paper IV also included the development of a novel interpretation of an artificial neural network as well as a model organism. The findings of the included papers are contextualized with a historical background looking back more than 2000 years and also with a theoretical background in neuroscience, genetics and mathematics. All in all trying to present a multifaceted but relevant discourse on the topic of information integration in the nervous system. The results of the included papers are in favour of the holistic interpretation. A holistic functional brain organization must thus be seen as plausible and with it follows consequences for how information processing can occur in the network of the nervous system and also how a functional decomposition might be possible, or impossible, to perform. One such consequence is that the neocortex should be seen as an indivisible unit of a dynamic system.
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| 9. |
- Enander, Jonas, et al.
(author)
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Integrated Sachs-Wolfe effect in massive bigravity
- 2015
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In: Physical Review D. - 1550-7998 .- 1550-2368. ; 91:8
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Journal article (peer-reviewed)abstract
- We study the integrated Sachs-Wolfe (ISW) effect in ghost-free, massive bigravity. We focus on the infinite-branch bigravity (IBB) model which exhibits viable cosmic expansion histories and stable linear perturbations, while the cosmological constant is set to zero and the late-time accelerated expansion of the Universe is due solely to the gravitational interaction terms. The ISW contribution to the CMB auto-correlation power spectrum is predicted, as well as the cross-correlation between the CMB temperature anisotropies and large-scale structure. We use ISW amplitudes as inferred from the WMAP 9-year temperature data together with galaxy and AGN data provided by the WISE mission in order to compare the theoretical predictions to the observations. The ISW amplitudes in IBB are found to be larger than the corresponding ones in the standard Lambda CDM model by roughly a factor of 1.5, but are still consistent with the observations.
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| 10. |
- Enander, Jonas, et al.
(author)
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Integrated Sachs-Wolfe effect in massive bigravity
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Other publication (other academic/artistic)abstract
- We study the Integrated Sachs-Wolfe (ISW) effect in ghost-free, massive bigravity, where only one metric couples to matter. We focus on the infinite-branch bigravity (IBB) model which exhibits viable cosmic expansion histories and stable linear perturbations, while the cosmological constant is set to zero and the late-time accelerated expansion of the Universe is due solely to the gravitational interaction terms. The ISW contribution to the CMB auto-correlation power spectrum is predicted, as well as the cross-correlation between the CMB temperature anisotropies and the large-scale structure. We use ISW amplitudes as observed in the WMAP 9-year temperature data together with galaxy and AGN data provided by the WISE mission, in order to compare the theoretical predictions to the observations. The ISW amplitudes in IBB are found to be larger than the corresponding ones in the standard LCDM model by roughly a factor of 1.5, but are still consistent with the observations.
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