| 1. |
- Andreasson, Håkan, 1966
(författare)
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Black Hole Formation from a Complete Regular Past for Collisionless Matter
- 2012
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Ingår i: Annales Henri Poincaré. - : Springer Science and Business Media LLC. - 1424-0637 .- 1424-0661. ; 13:7, s. 1511-1536
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Tidskriftsartikel (refereegranskat)abstract
- Initial data for the spherically symmetric Einstein-Vlasov system is constructed whose past evolution is regular and whose future evolution contains a black hole. This is the first example of initial data with these properties for the Einstein-matter system with a "realistic" matter model. One consequence of the result is that there exists a class of initial data for which the ratio of the Hawking mass mIS= mIS (r) and the area radius r is arbitrarily small everywhere, such that a black hole forms in the evolution. This result is in a sense analogous to the result (Christodoulou Commun Pure Appl Math 44:339-373, 1991) for a scalar field. Another consequence is that there exist black hole initial data such that the solutions exist for all Schwarzschild time .
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| 2. |
- Andreasson, Håkan, 1966, et al.
(författare)
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Bounds on M/R for charged objects with positive cosmological constant
- 2012
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Ingår i: Classical and Quantum Gravity. - : IOP Publishing. - 0264-9381 .- 1361-6382. ; 29:9
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Tidskriftsartikel (refereegranskat)abstract
- We consider charged spherically symmetric static solutions of the Einstein-Maxwell equations with a positive cosmological constant Lambda. If r denotes the area radius, m(g) and q the gravitational mass and charge of a sphere with area radius r respectively, we find that for any solution which satisfies the condition p + 2p(perpendicular to) +/- <= rho, where p >= 0 and p(perpendicular to) are the radial and tangential pressures respectively, rho >= 0 is the energy density, and for which 0 <= q(2)/r(2) + Lambda r(2) <= 1, the inequality m(g)/r <= 2/9 + q(2)/3r(2)-Lambda r(2)/3 + 2/9 root 1 + 3q(2)/r(2) + 3 Lambda r(2) holds. We also investigate the issue of sharpness, and we showthat the inequality is sharp in a few cases but generally this question is open.
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| 3. |
- Andréasson, Håkan, et al.
(författare)
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Cytoreductive surgery in pseudomyxoma peritonei-aspects of the learning curve
- 2013
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Ingår i: European Journal of Surgical Oncology. - : Elsevier BV. - 0748-7983 .- 1532-2157. ; 40:8, s. 930-936
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Tidskriftsartikel (refereegranskat)abstract
- Background: Cytoreductive surgery (CRS) plus perioperative intraperitoneal chemotherapy is a highly invasive treatment of peritoneal metastasis and requires many surgical procedures before mastering. The aim of this study was to estimate how many procedures are needed before stabilization can be seen in surgical outcome (R1 surgery, adverse events and bleeding) in patients with pseudomyxoma peritonei (PMP). Patients and methods: All 128 patients with PMP who were treated with CRS alone or CRS plus perioperative intraperitoneal chemotherapy between 2003 and 2008 at the Uppsala University Hospital, Uppsala, Sweden, were included. The learning curve was calculated using the partial least square (PLS) and cumulative sum control chart (CUSUM) graph. Two groups were formed based on the results of the learning curve. The learning curve plateau was considered the same as the stabilization in the CUSUM graph. Group I consisted of patients included during the learning period (n = 73) and Group 11 of patients treated after the learning period ended (n = 55). Comparisons between the groups were made on surgical outcome, survival and adverse events. Results: Stabilization was seen after 220 +/- 10 procedures. A higher occurrence of R1 surgery was seen in Group H (80%) compared to Group I (48%; P = 0.0002). Overall survival increased at four years after surgery in Group H compared to Group I (80% vs. 63%; P = 0.02). Conclusion: CRS plus perioperative intraperitoneal chemotherapy is a highly demanding procedure that requires more than 200 procedures before optimisation in surgical outcome is seen.
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| 4. |
- Andreasson, Håkan, 1966, et al.
(författare)
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Existence of axially symmetric static solutions of the Einstein-Vlasov system
- 2011
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Ingår i: Commun. Math. Phys.. - : Springer Science and Business Media LLC. - 0010-3616 .- 1432-0916. ; 308, s. 23-47
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Tidskriftsartikel (refereegranskat)abstract
- We prove the existence of static, asymptotically flat non-vacuum spacetimes with axial symmetry where the matter is modeled as a collisionless gas. The axially symmetric solutions of the resulting Einstein-Vlasov system are obtained via the implicit function theorem by perturbing off a suitable spherically symmetric steady state of the Vlasov-Poisson system.
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| 5. |
- Andreasson, Håkan, 1966, et al.
(författare)
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Formation of trapped surfaces for the spherically symmetric Einstein-Vlasov system
- 2010
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Ingår i: Journal of Hyperbolic Differential Equations. - Göteborg : Chalmers University of Technology. - 0219-8916. ; 7:4, s. 707-731
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Tidskriftsartikel (refereegranskat)abstract
- We consider the spherically symmetric, asymptotically flat, non-vacuum Einstein equations, using as matter model a collisionless gas as described by the Vlasov equation. We find explicit conditions on the initial data which guarantee the formation of a trapped surface in the evolution which in particular implies that weak cosmic censorship holds for these data. We also analyze the evolution of solutions after a trapped surface has formed and we show that the event horizon is future complete. Furthermore we find that the apparent horizon and the event horizon do not coincide. This behavior is analogous to what is found in certain Vaidya spacetimes. The analysis is carried out in Eddington-Finkelstein coordinates.
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| 6. |
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| 7. |
- Andreasson, Håkan, 1966, et al.
(författare)
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Gravitational collapse and the formation of black holes for the spherically symmetric Einstein-Vlasov system.
- 2010
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Ingår i: Quarterly of Applied Mathematics. - 1552-4485. ; 68, s. 17-42
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Tidskriftsartikel (refereegranskat)abstract
- We review results on the spherically symmetric, asymptotically flat Einstein-Vlasov system. We focus on a recent result where we found explicit conditions on the initial data which guarantee the formation of a black hole in the evolution. Among these data there are data such that the corresponding solutions exist globally in Schwarzschild coordinates. We put these results into a more general context, and we include arguments which show that the spacetimes we obtain satisfy the weak cosmic censorship conjecture and contain a black hole in the sense of suitable mathematical definitions of these concepts which are available in the literature.
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| 8. |
- Andreasson, Håkan, et al.
(författare)
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Histopathological classification of pseudomyxoma peritonei and the prognostic importance of PINCH protein
- 2012
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Ingår i: Anticancer Research. - : International Institute of Anticancer Research (IIAR). - 0250-7005 .- 1791-7530. ; 32:4, s. 1443-1448
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Tidskriftsartikel (refereegranskat)abstract
- AIM: The aims of this study were i) to assess a new and more detailed histopathological classification and to analyze concordance between pathologists in the histopathological classification of pseudomyxoma peritonei (PMP); ii) to analyze the expression in the stroma of the particularly interesting new cysteine-histidine (PINCH) protein and its prognostic importance in PMP.MATERIALS AND METHODS: Surgical specimens from 81 patients, classified according to the Ronnett et al histopathological classification were compared to a new system with four groups ranging from indolent to aggressive growth patterns. PINCH protein expression was analyzed and was related to clinical variables.RESULTS: The new four-group classification provided better prognostic information than the classification according to Ronnett et al. (p=0.04). Expression of the PINCH protein in the stroma was found in 83% of the cases and was associated with high tumor burden (p=0.002) and a poor prognosis (p=0.04).CONCLUSION: The proposed new PMP classification system may provide additional prognostic information. PINCH protein is expressed in PMP and has prognostic information.
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| 9. |
- Andreasson, Håkan, 1966
(författare)
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On gravitational collapse and cosmic censorship for collisionless matter
- 2014
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Ingår i: International Journal of Geometric Methods in Modern Physics. - : World Scientific Pub Co Pte Lt. - 0219-8878 .- 1793-6977. ; 11:2
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Tidskriftsartikel (refereegranskat)abstract
- The weak cosmic censorship conjecture is a central open problem in classical general relativity. Under the assumption of spherical symmetry, Christodoulou has investigated the conjecture for two different matter models; a scalar field and dust. He has shown that the conjecture holds true for a scalar field but that it is violated in the case of dust. The outcome of the conjecture is thus sensitive to which model is chosen to describe matter. Neither a scalar field nor dust are realistic matter models. Collisionless matter, or Vlasov matter, is a simple matter model but can be considered to be realistic in the sense that it is used by astrophysicists. The present status on the weak cosmic censorship conjecture for the Einstein-Vlasov system is reviewed here.
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| 10. |
- Andréasson, Håkan, et al.
(författare)
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Outcome differences between debulking surgery and cytoreductive surgery in patients with pseudomyxoma peritonei
- 2012
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Ingår i: European Journal of Surgical Oncology. - : Elsevier BV. - 0748-7983 .- 1532-2157. ; 38:10, s. 962-968
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND:The aim of this study was to compare debulking surgery and cytoreductive surgery (CRS) in patients with Pseudomyxoma peritonei (PMP) regarding efficacy and safety.PATIENTS AND METHODS:Data were extracted from medical records and treatment outcomes were analyzed for all 152 patients with PMP who were scheduled for debulking surgery and intraperitoneal chemotherapy (IPC) or CRS and IPC at Uppsala University Hospital, Uppsala, Sweden, between September 1993 and December 2008.RESULTS:One hundred and ten patients (73%) were treated with CRS and IPC and 40 (27%) with debulking surgery and IPC. In two patients (1%), surgery was defined as open and close. Patients with CRS and IPC had a 74% 5-year overall survival (OS) rate compared with 40% for those treated with debulking surgery (P < 0.001). Patients with no residual macroscopic tumour (R1 resection) had a better 5-year OS rate of 94% compared with 28% for patients with macroscopic residual tumour (R2) (P < 0.001). Grades II-IV adverse events were seen in 29% of debulked patients and in 47% of CRS/IPC patients (P = 0.053).CONCLUSIONS:CRS and IPC seems more efficient than debulking surgery and IPC but with numerically higher morbidity. Therefore, if surgically possible, CRS should be the treatment of choice for PMP patients. However, debulking surgery may still be of benefit to selected patients for palliative purposes.
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