| 1. |
- Aleksich, Mariya, et al.
(författare)
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XFEL Microcrystallography of Self-Assembling Silver n-Alkanethiolates
- 2023
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Ingår i: Journal of the American Chemical Society. - 0002-7863. ; 145:31, s. 17042-17055
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Tidskriftsartikel (refereegranskat)abstract
- New synthetic hybrid materials and their increasing complexity have placed growing demands on crystal growth for single-crystal X-ray diffraction analysis. Unfortunately, not all chemical systems are conducive to the isolation of single crystals for traditional characterization. Here, small-molecule serial femtosecond crystallography (smSFX) at atomic resolution (0.833 Å) is employed to characterize microcrystalline silver n-alkanethiolates with various alkyl chain lengths at X-ray free electron laser facilities, resolving long-standing controversies regarding the atomic connectivity and odd-even effects of layer stacking. smSFX provides high-quality crystal structures directly from the powder of the true unknowns, a capability that is particularly useful for systems having notoriously small or defective crystals. We present crystal structures of silver n-butanethiolate (C4), silver n-hexanethiolate (C6), and silver n-nonanethiolate (C9). We show that an odd-even effect originates from the orientation of the terminal methyl group and its role in packing efficiency. We also propose a secondary odd-even effect involving multiple mosaic blocks in the crystals containing even-numbered chains, identified by selected-area electron diffraction measurements. We conclude with a discussion of the merits of the synthetic preparation for the preparation of microdiffraction specimens and compare the long-range order in these crystals to that of self-assembled monolayers.
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| 2. |
- Blaschke, David, et al.
(författare)
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1-2-3-flavor color superconductivity in compact stars
- 2008
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Ingår i: Journal of Physics G. - : IOP Publishing. - 0954-3899 .- 1361-6471. ; 35:10
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Tidskriftsartikel (refereegranskat)abstract
- We suggest a scenario where the three light quark flavors are sequentially deconfined under increasing pressure in cold asymmetric nuclear matter as, e.g., in neutron stars. The basis for our analysis is a chiral quark matter model of Nambu–Jona-Lasinio (NJL) type with diquark pairing in the single flavor color-spin-locking (CSL), 2-flavor (2SC) and 3-flavor color-flavor locking (CFL) channels, and a Dirac–Brueckner–Hartree–Fock (DBHF) approach in the nuclear matter sector. We find that nucleon dissociation sets in at about the saturation density, n0, when the down-quark Fermi sea is populated (d-quark dripline) due to the flavor asymmetry imposed by β-equilibrium and charge neutrality. At about 3n0 u-quarks appear forming a 2-flavor color superconducting (2SC) phase, while the s-quark Fermi sea is populated only at still higher baryon density. The hybrid star sequence has a maximum mass of 2.1 M. Two- and 3-flavor quark matter phases are found only in gravitationally unstable hybrid star solutions.
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| 3. |
- Blaschke, David, et al.
(författare)
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Accessibility of color superconducting quark matter phases in heavy-ion collisions
- 2010
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Ingår i: Acta Physica Polonica B Proceedings Supplement. - 1899-2358 .- 2082-7865. ; 3:3, s. 741-745
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Tidskriftsartikel (refereegranskat)abstract
- We discuss a hybrid equation of state (EoS) that fulfills constraints for mass-radius relationships and cooling of compact stars. The quark matter EoS is obtained from a Polyakov-loop Nambu-Jona-Lasinio (PNJL) model with color superconductivity, and the hadronic one from a relativistic mean-field (RMF) model with density-dependent couplings (DD-RMF). For the construction of the phase transition regions we employ here for simplicity a Maxwell construction. We present the phase diagram for symmetric matter which exhibits two remarkable features: (1) a "nose"-like structure of the hadronic-to-quark matter phase border with an increase of the critical density at temperatures below T \sim 150 MeV and (2) a high critical temperature for the border of the two-flavor color superconducting (2SC) phase, Tc >160 MeV. We show the trajectories of heavy-ion collisions in the plane of excitation energy versus baryon density calculated using the UrQMD code and conjecture that for incident energies of 4 . . . 8 A GeV as provided, e.g., by the Nuclotron-M at JINR Dubna or by lowest energies at the future heavy-ion collision experiments CBM at FAIR and NICA at JINR, the color superconducting quark matter phase becomes accessible.
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| 4. |
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| 5. |
- Blaschke, David, et al.
(författare)
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Color superconducting quark matter in compact stars
- 2008
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Ingår i: Exotic States of Nuclear Matter. - Hackensack, NJ : World Scientific and Engineering Academy and Society. - 9789812797049 ; , s. 256-263
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Konferensbidrag (refereegranskat)
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| 6. |
- Blaschke, David, et al.
(författare)
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Diquark condensation effects on hot quark star configurations
- 2004
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Ingår i: Nuclear Physics A. - : Elsevier BV. - 0375-9474 .- 1873-1554. ; 736:1-2, s. 203-219
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Tidskriftsartikel (refereegranskat)abstract
- The equation of state for quark matter is derived for a nonlocal, chiral quark model within the mean field approximation. We investigate the effects of a variation of the formfactors of the interaction on the phase diagram of quark matter. Special emphasis is on the occurrence of a diquark condensate which signals a phase transition to color superconductivity and its effects on the equation of state under the condition of β-equilibrium and charge neutrality. We calculate the quark star configurations by solving the Tolman-Oppenheimer-Volkoff equations and obtain for the transition from a hot, normal quark matter core of a protoneutron star to a cool diquark condensed one a release of binding energy of the order of ΔMc2˜1053 erg. We find that this energy could not serve as an engine for explosive phenomena since the phase transition is not first order. Contrary to naive expectations the mass defect increases when for a given temperature we neglect the possibility of diquark condensation.
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| 7. |
- Blaschke, David, et al.
(författare)
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Diquark properties and the TOV equations
- 2001
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Ingår i: Proceedings of the Conference on Compact Stars in the QCD Phase Diagram (CSQCD), Copenhagen, Denmark, August 15 - 18, 2001. ; , s. 167-173
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Konferensbidrag (refereegranskat)abstract
- We present various results from including diquark properties and the gap equations into the TOV equations for compact quark objects. One such property is the diquark form factor, which has a strong influence on various quantities. We discuss the consequences for quark stars.
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| 8. |
- Blaschke, David, et al.
(författare)
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Equation of state at high densities and modern compact star observations
- 2008
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Ingår i: Journal of Physics G. - : IOP Publishing. - 0954-3899 .- 1361-6471. ; 35:1, s. 014051-6
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Tidskriftsartikel (refereegranskat)abstract
- Recently, observations of compact stars have provided new data of high accuracy which put strong constraints on the high-density behaviour of the equation of state of strongly interacting matter otherwise not accessible in terrestrial laboratories. The evidence for neutron stars with high mass (M = 2.1 +/- 0.2 M-circle dot for PSR J0751 + 1807) and large radii (R > 12 km for RX J1856-3754) rules out soft equations of state and has provoked a debate whether the occurrence of quark matter in compact stars can be excluded as well. In this contribution, it is shown that modern quantum field theoretical approaches to quark matter including colour superconductivity, and a vector meanfield allow a microscopic description of hybrid stars which fulfil the new, strong constraints. The deconfinement transition in the resulting stiff hybrid equation of state is weakly first order so that its signals have to be expected due to specific changes in transport properties governing the rotational and cooling evolution caused by the colour superconductivity of quark matter. A similar conclusion holds for the investigation of quark deconfinement in future generations of nucleus-nucleus collision experiments at low temperatures and high baryon densities such as CBM @ FAIR.
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| 9. |
- Blaschke, David, et al.
(författare)
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Sequential deconfinement of quark flavors in neutron stars
- 2009
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Ingår i: Physical Review C. Nuclear Physics. - 0556-2813 .- 1089-490X. ; 80:6, s. 65807-
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Tidskriftsartikel (refereegranskat)abstract
- A scenario is suggested in which the three light quark flavors are sequentially deconfined under increasing pressure in cold asymmetric nuclear matter as found, for example, in neutron stars. The basis for this analysis is a chiral quark matter model of Nambu–Jona-Lasinio (NJL) type with diquark pairing in the spin-1 single-flavor, spin-0 two-flavor, and three-flavor channels. Nucleon dissociation sets in at about the saturation density, n0, when the down-quark Fermi sea is populated (d-quark drip line) because of the flavor asymmetry induced by β equilibrium and charge neutrality. At about 3n0, u-quarks appear and a two-flavor color superconducting (2SC) phase is formed. The s-quark Fermi sea is populated only at still higher baryon density, when the quark chemical potential is of the order of the dynamically generated strange quark mass. Two different hybrid equations of state (EOSs) are constructed using the Dirac-Brueckner Hartree-Fock (DBHF) approach and the EOS of Shen et al. [H. Shen, H. Toki, K. Oyamatsu, and K. Sumiyoshi, Nucl. Phys. A637, 435 (1998)] in the nuclear matter sector. The corresponding hybrid star sequences have maximum masses of 2.1 and 2.0 M respectively. Two- and three-flavor quark-matter phases exist only in gravitationally unstable hybrid star solutions in the DBHF case, whereas the Shen-based EOSs produce stable configurations with a 2SC phase component in the core of massive stars. Nucleon dissociation via d-quark drip could act as a deep crustal heating process, which apparently is required to explain superbursts and cooling of x-ray transients.
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| 10. |
- Blaschke, David, et al.
(författare)
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Single-flavor CSL phase in compact stars
- 2008
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Ingår i: Hadronic physics. - Melville, NY : American Institute of Physics (AIP). - 9780735405622 ; , s. 183-192
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Konferensbidrag (refereegranskat)abstract
- We suggest a scenario where the three light quark flavors are sequentially deconfined under increasing pressure in cold asymmetric nuclear matter as, e.g., in neutron stars. The basis for our analysis is a chiral quark matter model of Nambu-Jona-Lasinio (NJL) type with diquark pairing in the spin-1 single flavor (CSL), spin-0 two flavor (2SC) and three flavor (CFL) channels. We find that nucleon dissociation sets in at about the saturation density, n0, when the down-quark Fermi sea is populated (d-quark dripline) due to the flavor asymmetry induced by β-equilibrium and charge neutrality. At about 3n0 u-quarks appear and a two-flavor color superconducting (2SC) phase is formed. The s-quark Fermi sea is populated only at still higher baryon density, when the quark chemical potential is of the order of the dynamically generated strange quark mass. We construct two different hybrid equations of state (EoS) using the Dirac-Brueckner Hartree-Fock (DBHF) approach and the EoS by Shen et al. in the nuclear matter sector. The corresponding hybrid star sequences have maximum masses of, respectively, 2.1 and 2.0 M⊙. Two- and three-flavor quark-matter phases exist only in gravitationally unstable hybrid star solutions in the DBHF case, while the Shen-based EoS produce stable configurations with a 2SC phase component in the core of massive stars. Nucleon dissociation due to d-quark drip at the crust-core boundary fulfills basic criteria for a deep crustal heating process which is required to explain superbusts as well as cooling of X-ray transients.
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