| 1. |
- Ajazi, Fioralba, et al.
(författare)
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Phase transition in random distance graphs on the torus
- 2017
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Ingår i: Journal of Applied Probability. - : Cambridge University Press (CUP). - 0021-9002 .- 1475-6072. ; 54:4, s. 1278-1294
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Tidskriftsartikel (refereegranskat)abstract
- In this paper we consider random distance graphs motivated by applications in neurobiology. These models can be viewed as examples of inhomogeneous random graphs, notably outside of the so-called rank-1 case. Treating these models in the context of the general theory of inhomogeneous graphs helps us to derive the asymptotics for the size of the largest connected component. In particular, we show that certain random distance graphs behave exactly as the classical ErdÅ's-Rényi model, not only in the supercritical phase (as already known) but in the subcritical case as well.
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| 2. |
- Ajazi, Fioralba, et al.
(författare)
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Structure of a randomly grown 2-d network.
- 2015
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Ingår i: BioSystems. - : Elsevier BV. - 1872-8324 .- 0303-2647. ; 136:Online 14 September 2015, s. 105-112
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Tidskriftsartikel (refereegranskat)abstract
- We introduce a growing random network on a plane as a model of a growing neuronal network. The properties of the structure of the induced graph are derived. We compare our results with available data. In particular, it is shown that depending on the parameters of the model the system undergoes in time different phases of the structure. We conclude with a possible explanation of some empirical data on the connections between neurons.
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| 3. |
- Ajdari, Sima, 1985, et al.
(författare)
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Evaluation of Operating and Design Parameters of Pressurized Flue Gas Systems with Integrated Removal of NO x and so x
- 2019
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Ingår i: Energy & Fuels. - : American Chemical Society (ACS). - 1520-5029 .- 0887-0624. ; 33:4, s. 3339-3348
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Tidskriftsartikel (refereegranskat)abstract
- This study investigates the operating and design parameters of product gas compression and integrated control of nitrogen oxides (NO x ) and sulfur oxides (SO x ) in large-scale oxy-fuel and chemical looping combustion processes. A process model that includes a comprehensive description of nitrogen and sulfur chemistry and mass transfer is developed. The results show that the fraction of NO oxidation into NO 2 will be 10-50% in a multistage compressor to 30 bars (1-4% O 2 in the gas) depending on the residence times in intercoolers and pressure levels. At lower O 2 concentrations (>0.1% O 2 in the gas), the oxidation is limited but still active. Nitric acid formation in the compressor condensate is, thus, inevitable, although limited, as most water is condensed in the early stages, whereas the acid gases are formed in the later stages. The NO 2 /NO x ratio has an important effect on the total amount of NO x absorbed and extra residence time should be added after the compressor to increase this ratio. Evaluation of the process behavior in relation to simultaneous absorption of SO 2 and NO x revealed that increased SO 2 /NO x ratio and bottom liquid recycling enhanced the total NO x absorption. In addition, maintaining the pH in the absorbing solution above 5 improves the removal efficiencies of NO x and SO 2 . NO x removal rates of up to around 95% can be achieved for SO 2 /NO x > 1 in the flue gas with appropriate design of the absorber. For SO 2 /NO x < 1, increasing the packing height or addition of S(IV) solutions could enhance the NO x removal rates to 95% or more. The model predictions are compared with the experimental data from a laboratory-scale absorber. The process model developed in this work enables design studies and techno-economic evaluation of absorption-based NO x and SO x removal concepts.
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| 4. |
- Ajdari, Sima, 1985, et al.
(författare)
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Formation and Control of NOx and SOx in Pressurized Oxy-Combustion Systems
- 2015
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Ingår i: The Proceedings of the 40th International Technical Conference on Clean Coal & Fuel Systems, 31 May-4 June 2015, Clearwater, Florida, USA.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The formation and control of NOx and SOx in pressurized oxy-fuel combustion systems is discussed in the present work. The chemistry of nitrogen and sulfur species under pressurized conditions and the experiences gained from operating atmospheric oxy-fuel combustion pilot plants are reviewed in brief. In a conventional combustion and gas cleaning process, SO2 and NO are the principle NOx and SOx species. However, the oxidation of NO to NO2 and SO2 to SO3 is favored by low temperature and high pressure. In the present paper we will make a first modelling based of the altered oxidation conditions during both high and low temperature conditions in pressurized oxy-combustion. Besides the gas-phase oxidation, the liquid-phase N-S interactions will further enhance the formation of acids in the flue gas condensate. Thus, these low and high temperature processes will be discussed in the present work due to their relevance for the design of the flue gas compression and gas cleaning system in pressurized oxy-combustion.
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| 5. |
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| 6. |
- Andersson, Karin, 1952, et al.
(författare)
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Environmental trade-offs in nitrogen oxide removal from ship engine emissions
- 2011
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Ingår i: Proceedings of the Institution of Mechanical Engineers Part M: Journal of Engineering for the Maritime Environment. - 2041-3084 .- 1475-0902. ; 225:1, s. 33-42
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Konferensbidrag (refereegranskat)abstract
- The emissions of nitrogen oxides (NOx) from ship engines constitute an increasing part of the total global emissions of NOx while the share from land-based sources is decreasing. In the coming years, new regulations will set limits to emissions in specific areas and various technical countermeasures will be developed and implemented. However, when taking technical measures against emissions on a local scale, there is always a risk of inducing an increase in the total environmental impact related to the technology used, owing to increased energy use and emissions in other places.In the present study, an investigation of the difference in environmental impact from passenger transport vessels with and without catalytic NOx emission purification was performed in a life cycle assessment. The production and transport of chemicals used in the catalyst are included in the study.The study shows that the use of selective catalytic reduction (SCR) gives a considerable decrease in the environmental impact compared with using a diesel engine without a catalyst. The transport of urea solution over a 500 km distance makes a very small contribution to the total environmental impact. The global warming potential is the only impact category for which values are increased when including the urea production and transport. When looking at the contribution from urea to the total impact from the SCR process, the increase is less than 10 per cent for most impact categories.
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| 7. |
- Andersson, Kristofer, et al.
(författare)
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Mutations in COL1A1 and COL1A2 and dental aberrations in children and adolescents with osteogenesis imperfecta - A retrospective cohort study
- 2017
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Ingår i: PLOS ONE. - : PUBLIC LIBRARY SCIENCE. - 1932-6203. ; 12:5
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Tidskriftsartikel (refereegranskat)abstract
- Osteogenesis imperfecta (OI) is a heterogeneous group of disorders of connective tissue, caused mainly by mutations in the collagen I genes (COL1A1 and COL1A2). Dentinogenesis imperfecta (DGI) and other dental aberrations are common features of OI. We investigated the association between collagen I mutations and DGI, taurodontism, and retention of permanent second molars in a retrospective cohort of 152 unrelated children and adolescents with OI. The clinical examination included radiographic evaluations. Teeth from 81 individuals were available for histopathological evaluation. COL1A1/2 mutations were found in 104 individuals by nucleotide sequencing. DGI was diagnosed clinically and radiographically in 29% of the individuals (44/152) and through isolated histological findings in another 19% (29/152). In the individuals with a COL1A1 mutation, 70% (7/10) of those with a glycine substitution located C-terminal of p. Gly305 exhibited DGI in both dentitions while no individual (0/7) with a mutation N-terminal of this point exhibited DGI in either dentition (p = 0.01). In the individuals with a COL1A2 mutation, 80% (8/10) of those with a glycine substitution located C terminal of p. Gly211 exhibited DGI in both dentitions while no individual (0/5) with a mutation N-terminal of this point (p = 0.007) exhibited DGI in either dentition. DGI was restricted to the deciduous dentition in 20 individuals. Seventeen had missense mutations where glycine to serine was the most prevalent substitution (53%). Taurodontism occurred in 18% and retention of permanent second molars in 31% of the adolescents. Dental aberrations are strongly associated with qualitatively changed collagen I. The varying expressivity of DGI is related to the location of the collagen I mutation. Genotype information may be helpful in identifying individuals with OI who have an increased risk of dental aberrations.
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| 8. |
- Andersson, Kristin, et al.
(författare)
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Prospective study of genital human papillomaviruses and nonmelanoma skin cancer.
- 2013
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Ingår i: International Journal of Cancer. - : Wiley. - 0020-7136 .- 1097-0215. ; 133:8, s. 1840-1845
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Tidskriftsartikel (refereegranskat)abstract
- Genital high-risk human papillomaviruses (HPVs) cause cervical cancer and are also found in a small proportion of nonmelanoma skin cancers (NMSCs). We used cancer registry linkages to follow the 856,000 serum donors included in the Southern Sweden Microbiology Biobank or the Janus Biobank in Norway, for incident skin cancers occurring up to 30 years after serum donation. Serum samples taken before diagnosis of squamous cell carcinoma (SCC) (N = 633), basal cell carcinoma (BCC) (N = 1990) or other NMSC (N = 153) and matched samples from control donors were tested for antibodies to the genital HPV types 16 and 18. Both HPV 16 and 18 were associated with increased risk for SCC [odds ratio (OR) 1.6, 95% confidence interval (CI) 1.1-2.6 and OR 1.7, 95% CI 1.1-2.5, respectively] and other NMSC (OR 2.3, 95% CI 1.0-5.2 and OR 3.5, 95% CI 1.4-8.7, respectively), but not for BCC. Tumor blocks from HPV16 or 18 seropositive cases were tested with real-time polymerase chain reaction for presence of HPV16 or 18 DNA. No HPV18 DNA was found and only four of 79 SCC cases (two of which were from the perineum/perianal area), one of 221 BCC cases and zero of five cases with other NMSC contained HPV16 DNA. In conclusion, we found prospective evidence that HPV16 and 18 antibodies associate with SCC and other NMSC risk, but not with BCC risk. As only a small proportion of seropositive subjects had evidence of the corresponding HPV DNA in the tumor, most of this excess risk is likely to be due to confounders associated with genital HPV infection.
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| 9. |
- Andersson, Kristin, et al.
(författare)
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Prospective Study of Human Papillomavirus Seropositivity and Risk of Nonmelanoma Skin Cancer
- 2012
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Ingår i: American Journal of Epidemiology. - : Oxford University Press (OUP). - 0002-9262 .- 1476-6256. ; 175:7, s. 685-695
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Tidskriftsartikel (refereegranskat)abstract
- Cutaneous human papillomaviruses (HPVs) have been associated with squamous cell carcinoma (SCC) in case-control studies, but there are limited data from prospective studies assessing whether virus exposure predicts risk of future cancer development. Two major biobanks, the Southern Sweden Microbiology Biobank (1971-2003) and the Janus Biobank (1973-2003) in Norway, containing samples from 850,000 donors, were searched for incident skin cancer for up to 30 years using registry linkages. Altogether, 2,623 donors with samples taken before diagnosis of SCC or basal cell carcinoma (BCC) of the skin were identified. Prediagnostic samples and samples from 2,623 matched controls were tested for antibodies against 33 types of HPV. Baseline seropositivity to HPV types in genus beta species 2 was associated with SCC risk (odds ratio = 1.3, 95% confidence interval: 1.1, 1.7); this was also the case for samples taken more than 18 years before diagnosis (odds ratio = 1.8, 95% confidence interval: 1.1, 2.8). Type-specific persistent seropositivity entailed elevated point estimates for SCC risk for 29 HPV types and decreased point estimates for only 3 types. After multiple hypothesis adjustment, HPV 76 was significantly associated with SCC risk and HPV 9 with BCC risk. In summary, seropositivity for certain HPV types was associated with an increased risk for future development of SCC and BCC.
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| 10. |
- Andersson, Kristina, et al.
(författare)
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Public Procurement and Geofencing – lessons learned from a pilot with geofencing of service trips
- 2024
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- The city of Gothenburg public procured geofencing technology and did a pilot during fall 2022 with geofenced service trips vehicles (retrofitted). This report investigates the challenges and opportunities associated with procuring geofencing technology, addressing aspects such as needs, market analysis, risk, alternative solutions, legislative framework, and much more based on lessons learned from the pilot. Geofencing, defined as the creation of virtual boundaries to monitor, inform, and control traffic using electronic communication technologies or predefined boundaries within vehicles, lacks standardization and comprises various technical solutions. Its functionality depends on digital mapping, vehicle tracking methods like GNSS, onboard equipment, real-time connectivity, and additional databases for traffic rules. Geofencing offers degrees of control, from informing and alerting drivers about speed limits to actively restricting vehicle speed, with possibilities for static, dynamic, and smart adaptations. Applications range from enhancing traffic safety by alerting drivers and controlling vehicle speed to improving transport efficiency through optimized route selection and environmental benefits by reducing emissions and noise pollution. However, regulatory challenges persist, such as the absence of type-approved geofencing equipment and the need to define functional requirements rather than specific technologies in legal frameworks, presenting both opportunities and obstacles for its implementation in road traffic management and procurement processes. The first step in public procurement involves laying the groundwork by comprehensively understanding the buying organization's needs and market capabilities to meet them. The city identified key goals such as safe travel and driver assistance. The city explored existing agreements and engaged operators for a geofencing pilot to address speed compliance and traffic safety concerns, alongside researching market options and risks associated with third-party equipment installation and data privacy. Alternatives like ISA and ADAS were considered but deemed insufficient. In the second step the procurement is carried out, which includes tasks such as producing procurement documents, advertising, evaluating tenders, and ultimately selecting a supplier. The city procured the geofencing technology by direct public procurement and used a traditional public procurement to get hold of vehicles and drivers. In the third step of the public procurement implementation is in focus on, executing the pilot and evaluating its outcomes, particularly concerning geofencing technology. Challenges arose during implementation, including difficulties in accurately mapping zones to individual vehicles due to problems with the speed box installed. The city of Gothenburg learned valuable lessons, highlighting the importance of direct communication with drivers, verifying technology before widespread adoption, and close collaboration between all stakeholders. Despite challenges, the pilot provided valuable data and insights, with recommendations offered for future geofencing initiatives, emphasizing early supplier dialogue, thorough testing, user experience understanding, and involving relevant stakeholders from the outset. In this report insights, advice and lessons learned are also shared. Technical hurdles include the lack of standardized geofencing, difficulty in retrofitting diverse vehicle fleets, and limited market availability. Organizational challenges encompass the need for a needs-driven approach, internal and external collaboration, and balancing technology with user acceptance. Concerns about data privacy and driver behaviour emerge, requiring careful navigation of GDPR regulations. Strategically deciding the city's role in IT-solutions, data collection, and responsibility for vehicle behaviour poses business-related challenges. The report concludes that while geofencing technology isn't yet ready for full-scale implementation, further pilots are necessary for development. Future work involves exploring alternative solutions, enhancing internal processes, and conducting larger pilots to advance understanding and implementation of geofencing technology.
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