Photoionization model for streamer propagation mode change in simulation model for streamers in dielectric liquids

Radiation is important for the propagation of streamers in dielectric liquids. Photoionization is a possibility, but the effect is difficult to differentiate from other contributions. In this work, we model radiation from the streamer head, causing photoionization when absorbed in the liquid. We find that photoionization is local in space (μm-scale). The radiation absorption cross section is modeled considering that the ionization potential (IP) is dependent on the electric field. The result is a steep increase in the ionization rate when the electric field reduces the IP below the energy of the first electronically excited state, which is interpreted as a possible mechanism for changing from slow to fast streamers. By combining a simulation model for slow streamers based on the avalanche mechanism with a change to fast mode based on a photoionization threshold for the electric field, we demonstrate how the conductivity of the streamer channel can be important for switching between slow and fast streamer propagation modes.publishedVersio

Engineering strategies for ABD-derived affinity proteins for therapeutic and diagnostic applications

Small stable protein domains are attractive scaffolds for engineering affinity proteins due to their high tolerance to mutagenesis without loosing structural integrity. The albuminbinding domain is a 5 kDa three-helix bundle derived from the bacterial receptor Protein G with low-nanomolar affinity to albumin. In this thesis, the albumin-binding domain is explored as a scaffold for engineering novel affinity proteins with the possible benefit of combining a prolonged serum half-life with specific targeting in a single small scaffold protein. Previously, a library was created by randomizing surface-exposed residues in order to engineer affinity to a new target antigen in addition to the inherent albumin affinity. Here, phage display selections were separately performed against the tumor antigens ERBB2 and ERBB3. The ERBB3 selection resulted in a panel of candidates that were found to have varying affinities to ERBB3 in the nanomolar range, while still retaining a high affinity to albumin. Further characterization concluded that the clones also competed for binding to ERBB3 with the natural activating ligand Heregulin. The selections against ERBB2 resulted in sub-nanomolar affinities to ERBB2 where the binding site was found to overlap with the antibody Trastuzumab. The binding sites on ABD to albumin and either target were found in both selections to be mutually exclusive, as increased concentrations of albumin reduced the level of binding to ERBB2 or ERBB3. An affinity-matured ERBB2 binder, denoted ADAPT6, which lacked affinity to albumin was evaluated as a radionuclide-labeled imaging tracer for diagnosing ERBB2-positive tumors. Biodistribution studies in mice showed a high renal uptake consistent with affinity proteins in the same size range and the injected ADAPT quickly localized to the implanted tumor. High contrast images could be generated and ERBB2-expressing tissue could be distinguished from normal tissue with high contrast, demonstrating the feasibility of the scaffold for use as diagnostic tool. In a fourth study, affinity maturation strategies using staphylococcal cell-surface display were evaluated by comparing two replicate selections and varying the stringency. A sub-nanomolar target concentration was concluded to be inappropriate for equilibrium selection as the resulting output was highly variable between replicates. In contrast, equilibrium sorting at higher concentrations followed by kinetic-focused off-rate selection resulted in high output overlap between attempts and a clear correlation between affinity and enrichment.QC 20160510</p

Surrogate models for design and study of underground mine ventilation

Ventilation is vital for the production in an underground mine. Therefore, it is important to have efficient and accurate design tools in order to ensure and optimize the airflows in the mine. There are several commercial software for airflow simulation based on first principles. However, the computational cost of simulation together with integrational obstacles when connecting simulation to control strategies limits the benefit of these tools. In this paper an approach utilizing surrogate models as a complementary design tool is presented. It is shown that using surrogate models one can with rather low computational expense evaluate and benchmark different control strategies. It is also shown that the models can be used for identifying possible bottlenecks in the system in advance. Moreover, the use of surrogate models transfer the simulation into a development-friendly environment (such as Matlab). A test case is used based on a real underground mine ventilation design. Two types of surrogate models are fitted to process data; multiple least squares regression and a Gaussian process model. Sensitivity analysis on the surrogate shows the potential of using surrogate models for identifying bottlenecks. Furthermore, the surrogate is used to benchmark two different control strategies for mine ventilation.QC 20210810</p

Simulation model for the propagation of second mode streamers in dielectric liquids using the Townsend-Meek criterion

publishedVersio

Photoionization model for streamer propagation mode change in simulation model for streamers in dielectric liquids

Radiation is important for the propagation of streamers in dielectric liquids. Photoionization is a possibility, but the effect is difficult to differentiate from other contributions. In this work, we model radiation from the streamer head, causing photoionization when absorbed in the liquid. We find that photoionization is local in space (μm-scale). The radiation absorption cross section is modeled considering that the ionization potential (IP) is dependent on the electric field. The result is a steep increase in the ionization rate when the electric field reduces the IP below the energy of the first electronically excited state, which is interpreted as a possible mechanism for changing from slow to fast streamers. By combining a simulation model for slow streamers based on the avalanche mechanism with a change to fast mode based on a photoionization threshold for the electric field, we demonstrate how the conductivity of the streamer channel can be important for switching between slow and fast streamer propagation modes.publishedVersio

Modeling the transition to fast mode streamers in dielectric liquids

A simplified model for photoionization, modeling fast streamer propagation, is combined with an existing model for slow streamers, based on electron avalanches. Transitions from fast mode to slow mode, and from slow mode to fast mode, are investigated.acceptedVersio

Vasomotor symptoms usually reappear after cessation of postmenopausal hormone therapy : a Swedish population-based study.

OBJECTIVE:: The purpose of this study was to investigate the extent of reappearance of vasomotor symptoms after cessation of postmenopausal hormone therapy (HT) in women who started HT because of hot flashes. METHODS:: A cross-sectional postal survey was conducted. A validated questionnaire was sent to all women 53 to 54 years old living in Linköping, Sweden (n = 1,733), including questions about menopause, HT, and vasomotor symptoms. Pearson's chi test and logistic regression were used for statistical analyses. RESULTS:: Response rate after one reminder was 77.3%. After omitting incomplete answers, 72.9% remained for analysis. In all women, 319 (25.3%) were current users of HT, 242 (19.2%) were previous users, and 702 (55.6%) were never-users. Of the 242 previous users, 165 (69%) women stated that they had vasomotor symptoms before starting HT. Vasomotor symptoms recurred after cessation of HT in 143 (87%) of these 165 women. We found no significant difference in symptom recurrence in comparisons of the three groups based on usage of HT for 0 to 1, 2 to 4, or 5 years or more. CONCLUSIONS:: Most women who had vasomotor symptoms when they initiated HT reported recurrence of symptoms after cessation of HT (87%), although the flashes were usually reported to be less frequent and bothersome than they were before HT. Effective and safe treatment approaches for women with recurrence of vasomotor symptoms are needed.This is a non-final version of an article published in final form in:Lotta Lindh-Åstrand, Jan Brynhildsen, Mikael Hoffman and Mats Hammar, Vasomotor symptoms usually reappear after cessation of postmenopausal hormone therapy: a Swedish population-based study, 2009, Menopause (New York, N.Y.).http://dx.doi.org/10.1097/gme.0b013e3181a53221Copyright: Raven Press, Ltd

Risk communication in consultations about hormone therapy in the menopause – concordance in risk assessment and framing due to the context

Background It is important for the physician and the patient to have a mutual understanding of the possible consequences of different treatment alternatives in order to achieve a partnership in decision making. Objective The aim of this study was to explore to which degree first-time consultations for discussion of climacteric discomfort achieved shared understanding of the risks and benefits associated with hormone therapy in the menopausal transition (HT). Methods Analysis of structure and content of transcribed consultations (n=20), and follow-up interviews of the women (n=19 pairs of consultations and interviews), from first-time visits for discussion of climacteric discomfort and/or HT with five physicians at three different out-patient clinics of gynaecology in Sweden. Results Four distinctively different interpretations of risk, depending on whether or not benefits were discussed in the same context, emerged from the analysis. On average 5 advantages (range 0-11) and 2 (0-3) disadvantages were mentioned during the consultations. In the interviews the women expressed on average 4 advantages (0-7) and 1 disadvantage (0-3). There were major variations between advantages and disadvantages expressed in the consultation and the following interview. Conclusion Even though the consultations scored high in patient involvement, the information in most consultations was not structured in a way that made it possible to achieve a shared or an informed decision making.Original publication: Hoffmann M, Hammar M, Kjellgren K I, Lindh-Åstrand L and Ahlner J, Risk communication in consultations about hormone therapy in the menopause – concordance in risk assessment and framing due to the context, 2006, Climacteric, (9), 5, 347-354. http://dx.doi.org/10.1080/13697130600870220. Copyright © Taylor & Francis Group, an informa busines