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- Andreasson, Håkan, 1966
(författare)
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On Lorentz Invariance, Regularity and Global Existence for Kinetic Equations
- 1997
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- [A1] Regularity of the gain term and strong L1 convergence to equilibrium for the relativistic Boltzmann equation. The main purpose of the paper is to show that the gain term of the relativistic collision operator is regularizing. This is a generalization of P.L. Lions' analogous result in the nonrelativistic situation. The Lorentz invariance of relativistic particle dynamics plays an important role in the proof. The regularizing theorem has many applications in kinetic theory, some of which are discussed in the paper. In particular the asymptotic behaviour of periodic solutions to the relativistic Boltzmann equation is studied. It is shown that such solutions converge strongly in L^1 to a global Juttner equilibrium solution for arbitrary initial data. This extends earlier results for small data. [A2] Global existence of smooth solutions in three dimensions for the semiconductor Vlasov-Poisson-Boltzman equation. This paper shows global existence and uniqueness of smooth solutions in three dimensions for the semiconductor Vlasov-Poisson-Boltzmann equation. This extends an earlier result from the two-dimensional situation. Moreover, assumptions on the scattering kernel which limit the decay of the collision frequency are introduced, extending in part the assumptions used in the two-dimensional case. A slow decay of the collision frequency is important for studying fluid approximations under high electric fields of the Vlasov-Poisson-Boltzmann equation. [A3] Controlling the propagation of the support for the relativistic Vlasov equation with a selfconsistent Lorentz invariant field. The motivation for this paper comes from the fact that the successful techniques developed for controlling the propagation of the support for the classical Vlasov-Poisson equation (leading to global existence of smooth solutions) all fail for the relativistic Vlasov-Poisson equation. This equation lacks the Lorentz invariance. It has nevertheless been suggested that an understanding of this equation may be necessary for understanding the fundamental relativistic Vlasov-Maxwell equation. In the paper a new equation for the field is introduced which is Lorentz invariant. It is shown that the propagation of the support, for solutions satisfying this equation and the relativistic Vlasov equation, may be controlled. This is a strong indication that the transformation properties of the equations are important in studying existence of smooth solutions.
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| 2. |
- Andréasson, Håkan
(författare)
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Pseudomyxoma Peritonei : Aspects of Natural History, Learning Curve, Treatment Outcome and Prognostic Factors
- 2013
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Pseudomyxoma peritonei (PMP) is a rare disease characterized by mucinous peritoneal metastasis (PM). Different loco-regional treatment strategies, i.e. debulking surgery and cytoreductive surgery (CRS) in combination with hyperthermic intraperitoneal chemotherapy (HIPEC), have changed the prognosis for these patients. CRS is an aggressive surgical procedure with a long learning curve. PMP exists in different types; how many depends on which classification is used.The aims of this thesis were to investigate the time-frame of PMP development from an isolated appendiceal neoplasm, examine the learning process for CRS, evaluate the differences in treatment outcome between debulking surgery and CRS in combination with HIPEC, to evaluate a more detailed PMP classification and to investigate particularly interesting new cysteine-histidine (PINCH) protein as a prognostic factor for PMP.Retrospectively 26 PMP patients were identified as having had an appendectomy with a neoplasm in the appendix but with no evidence of PM at the appendectomy. They were treated for PMP within a median of 13.1 months (3.8-95.3) after the appendectomy. No difference was seen between the types of PMP regarding the time to a clinically significant development of PMP and how much tumour was found at treatment. CRS is a highly invasive treatment and stabilization in the learning curve was seen after 220±10 procedures. Patients treated with CRS+HIPEC had a better 5-year overall survival (OS) than patients treated with debulking surgery, 74% vs. 40%. CRS increased the rate of complete cytoreduction from 25% in patients treated with debulking surgery to 72%. The new four-grade PMP classification showed very good inter-rater agreement between two independent pathologists and a difference in survival rates was observed between the different grades. A positive PINCH staining was recorded in 83% of the tumours and that was associated with poorer survival.
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| 4. |
- Holmberg, Lina
(författare)
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Trauma Care - Implementation, Evaluation and Validation
- 2024
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Trauma is a major cause of death and morbidity in all ages, which makes continuous improvement of trauma care a high priority. During the last decades, Sweden’s trauma system has evolved with initiation of a national trauma registry (SweTrau) in 2011 and the Swedish National Trauma Triage criteria (SNTTC) in 2017. However, the Swedish trauma panorama has evolved as well, something this thesis aimed to explore, alongside with evaluating the safety and accuracy of the SNTTC and performing the first validation of SweTrau. Paper I is a prospective stepped-wedge cohort study, showing unchanged 30-day mortality, over- and undertriage after the implementation of the SNTTC, as well as a reduction of the lowest level of trauma call by almost 50%, proving that the SNTTC are safe to use. In Paper II, a retrospective multicentre cohort study, the SNTTC are further investigated, displaying a sensitivity of almost 85% while also assessing specificity, positive predictive value (PPV) and positive likelihood ratio (LR+). With no additional enhancing criteria found, the SNTTC are concluded to efficiently identify severely injured patients. Paper III reports the first validation of SweTrau; an on-site re-registration compared with the original registration in SweTrau. It demonstrates that the data in SweTrau is reliable, with high accuracy (85.8%), correctness (89.7%), data completeness (88.5%) and correlation (87.5%), while being comparable to international trauma registries using the Utstein template of trauma. Case completeness and timeliness are identified as areas of improvement. In Paper IV, nine-year trauma trends in two major trauma centres are analysed in a retrospective cohort study. A sharp reduction in intensive care unit admissions is seen, as well as a worrying increase in penetrating trauma (>50%) and mortality for patients with a low injury severity score (1.3%-2.7%, p=0.005), all of which require further investigation. In conclusion; this thesis has confirmed that the SNTTC are safe and efficient, as well as pin-pointed important trauma areas to focus on in the future. Finally, it has established the validity of the data in SweTrau - a major source of Swedish trauma research.
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