| 1. |
- Ademuyiwa, Adesoji O., et al.
(författare)
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Determinants of morbidity and mortality following emergency abdominal surgery in children in low-income and middle-income countries
- 2016
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Ingår i: BMJ Global Health. - : BMJ Publishing Group Ltd. - 2059-7908. ; 1:4
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Tidskriftsartikel (refereegranskat)abstract
- Background: Child health is a key priority on the global health agenda, yet the provision of essential and emergency surgery in children is patchy in resource-poor regions. This study was aimed to determine the mortality risk for emergency abdominal paediatric surgery in low-income countries globally.Methods: Multicentre, international, prospective, cohort study. Self-selected surgical units performing emergency abdominal surgery submitted prespecified data for consecutive children aged <16 years during a 2-week period between July and December 2014. The United Nation's Human Development Index (HDI) was used to stratify countries. The main outcome measure was 30-day postoperative mortality, analysed by multilevel logistic regression.Results: This study included 1409 patients from 253 centres in 43 countries; 282 children were under 2 years of age. Among them, 265 (18.8%) were from low-HDI, 450 (31.9%) from middle-HDI and 694 (49.3%) from high-HDI countries. The most common operations performed were appendectomy, small bowel resection, pyloromyotomy and correction of intussusception. After adjustment for patient and hospital risk factors, child mortality at 30 days was significantly higher in low-HDI (adjusted OR 7.14 (95% CI 2.52 to 20.23), p<0.001) and middle-HDI (4.42 (1.44 to 13.56), p=0.009) countries compared with high-HDI countries, translating to 40 excess deaths per 1000 procedures performed.Conclusions: Adjusted mortality in children following emergency abdominal surgery may be as high as 7 times greater in low-HDI and middle-HDI countries compared with high-HDI countries. Effective provision of emergency essential surgery should be a key priority for global child health agendas.
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| 2. |
- Burke, Sinead M., et al.
(författare)
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An experimental and modeling study of propene oxidation. Part 2: Ignition delay time and flame speed measurements
- 2015
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Ingår i: Combustion and Flame. - : Elsevier BV. - 0010-2180. ; 162:2, s. 296-314
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Tidskriftsartikel (refereegranskat)abstract
- Experimental data obtained in this study (Part II) complement the speciation data presented in Part I, but also offer a basis for extensive facility cross-comparisons for both experimental ignition delay time (IDT) and laminar flame speed (LFS) observables. To improve our understanding of the ignition characteristics of propene, a series of IDT experiments were performed in six different shock tubes and two rapid compression machines (RCMs) under conditions not previously studied. This work is the first of its kind to directly compare ignition in several different shock tubes over a wide range of conditions. For common nominal reaction conditions among these facilities, cross-comparison of shock tube IDTs suggests 20-30% reproducibility (2 sigma) for the IDT observable. The combination of shock tube and RCM data greatly expands the data available for validation of propene oxidation models to higher pressures (2-40 atm) and lower temperatures (750-1750 K). Propene flames were studied at pressures from 1 to 20 atm and unburned gas temperatures of 295-398 K for a range of equivalence ratios and dilutions in different facilities. The present propene-air LFS results at 1 atm were also compared to LFS measurements from the literature. With respect to initial reaction conditions, the present experimental LFS cross-comparison is not as comprehensive as the IDT comparison; however, it still suggests reproducibility limits for the LFS observable. For the LFS results, there was agreement between certain data sets and for certain equivalence ratios (mostly in the lean region), but the remaining discrepancies highlight the need to reduce uncertainties in laminar flame speed experiments amongst different groups and different methods. Moreover, this is the first study to investigate the burning rate characteristics of propene at elevated pressures (>5 atm). IDT and LFS measurements are compared to predictions of the chemical kinetic mechanism presented in Part I and good agreement is observed. (C) 2014 The Combustion Institute. Published by Elsevier Inc. All rights reserved.
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| 3. |
- Alonso-Fernandez, Fernando, 1978-, et al.
(författare)
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A Survey of Super-Resolution in Iris Biometrics with Evaluation of Dictionary-Learning
- 2019
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Ingår i: IEEE Access. - Piscataway, NJ : IEEE. - 2169-3536. ; 7, s. 6519-6544
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Tidskriftsartikel (refereegranskat)abstract
- The lack of resolution has a negative impact on the performance of image-based biometrics. While many generic super-resolution methods have been proposed to restore low-resolution images, they usually aim to enhance their visual appearance. However, an overall visual enhancement of biometric images does not necessarily correlate with a better recognition performance. Reconstruction approaches need thus to incorporate specific information from the target biometric modality to effectively improve recognition performance. This paper presents a comprehensive survey of iris super-resolution approaches proposed in the literature. We have also adapted an Eigen-patches reconstruction method based on PCA Eigentransformation of local image patches. The structure of the iris is exploited by building a patch-position dependent dictionary. In addition, image patches are restored separately, having their own reconstruction weights. This allows the solution to be locally optimized, helping to preserve local information. To evaluate the algorithm, we degraded high-resolution images from the CASIA Interval V3 database. Different restorations were considered, with 15 × 15 pixels being the smallest resolution evaluated. To the best of our knowledge, this is among the smallest resolutions employed in the literature. The experimental framework is complemented with six publicly available iris comparators, which were used to carry out biometric verification and identification experiments. Experimental results show that the proposed method significantly outperforms both bilinear and bicubic interpolation at very low-resolution. The performance of a number of comparators attain an impressive Equal Error Rate as low as 5%, and a Top-1 accuracy of 77-84% when considering iris images of only 15 × 15 pixels. These results clearly demonstrate the benefit of using trained super-resolution techniques to improve the quality of iris images prior to matching. © 2018, Emerald Publishing Limited.
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| 4. |
- Alonso-Fernandez, Fernando, 1978-, et al.
(författare)
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Eigen-patch iris super-resolution for iris recognition improvement
- 2015
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Ingår i: 2015 23rd European Signal Processing Conference (EUSIPCO). - Piscataway, NJ : IEEE Press. - 9780992862633 ; , s. 76-80
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Konferensbidrag (refereegranskat)abstract
- Low image resolution will be a predominant factor in iris recognition systems as they evolve towards more relaxed acquisition conditions. Here, we propose a super-resolution technique to enhance iris images based on Principal Component Analysis (PCA) Eigen-transformation of local image patches. Each patch is reconstructed separately, allowing better quality of enhanced images by preserving local information and reducing artifacts. We validate the system used a database of 1,872 near-infrared iris images. Results show the superiority of the presented approach over bilinear or bicubic interpolation, with the eigen-patch method being more resilient to image resolution reduction. We also perform recognition experiments with an iris matcher based 1D Log-Gabor, demonstrating that verification rates degrades more rapidly with bilinear or bicubic interpolation. ©2015 IEEE
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| 5. |
- Alonso-Fernandez, Fernando, 1978-, et al.
(författare)
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Improving Very Low-Resolution Iris Identification Via Super-Resolution Reconstruction of Local Patches
- 2017
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Ingår i: 2017 International Conference of the Biometrics Special Interest Group (BIOSIG). - Bonn : Gesellschaft für Informatik. - 9783885796640 - 9781538603963
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Konferensbidrag (refereegranskat)abstract
- Relaxed acquisition conditions in iris recognition systems have significant effects on the quality and resolution of acquired images, which can severely affect performance if not addressed properly. Here, we evaluate two trained super-resolution algorithms in the context of iris identification. They are based on reconstruction of local image patches, where each patch is reconstructed separately using its own optimal reconstruction function. We employ a database of 1,872 near-infrared iris images (with 163 different identities for identification experiments) and three iris comparators. The trained approaches are substantially superior to bilinear or bicubic interpolations, with one of the comparators providing a Rank-1 performance of ∼88% with images of only 15×15 pixels, and an identification rate of 95% with a hit list size of only 8 identities. © 2017 Gesellschaft fuer Informatik.
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| 6. |
- Alonso-Fernandez, Fernando, 1978-, et al.
(författare)
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Iris Super-Resolution Using Iterative Neighbor Embedding
- 2017
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Ingår i: 2017 IEEE Conference on Computer Vision and Pattern Recognition Workshops. - Los Alamitos : IEEE Computer Society. - 9781538607336 - 9781538607343 ; , s. 655-663
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Konferensbidrag (refereegranskat)abstract
- Iris recognition research is heading towards enabling more relaxed acquisition conditions. This has effects on the quality and resolution of acquired images, severely affecting the accuracy of recognition systems if not tackled appropriately. In this paper, we evaluate a super-resolution algorithm used to reconstruct iris images based on iterative neighbor embedding of local image patches which tries to represent input low-resolution patches while preserving the geometry of the original high-resolution space. To this end, the geometry of the low- and high-resolution manifolds are jointly considered during the reconstruction process. We validate the system with a database of 1,872 near-infrared iris images, while fusion of two iris comparators has been adopted to improve recognition performance. The presented approach is substantially superior to bilinear/bicubic interpolations at very low resolutions, and it also outperforms a previous PCA-based iris reconstruction approach which only considers the geometry of the low-resolution manifold during the reconstruction process. © 2017 IEEE
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| 7. |
- Alonso-Fernandez, Fernando, 1978-, et al.
(författare)
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Reconstruction of Smartphone Images for Low Resolution Iris Recognition
- 2015
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Ingår i: 2015 IEEE International Workshop on Information Forensics and Security (WIFS). - Piscataway, NJ : IEEE Press. - 9781467368025
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Konferensbidrag (refereegranskat)abstract
- As iris systems evolve towards a more relaxed acquisition, low image resolution will be a predominant issue. In this paper we evaluate a super-resolution method to reconstruct iris images based on Eigen-transformation of local image patches. Each patch is reconstructed separately, allowing better quality of enhanced images by preserving local information. We employ a database of 560 images captured in visible spectrum with two smartphones. The presented approach is superiorto bilinear or bicubic interpolation, especially at lower resolutions. We also carry out recognition experiments with six iris matchers, showing that better performance can be obtained at low-resolutions with the proposed eigen-patch reconstruction, with fusion of only two systems pushing the EER to below 5-8% for down-sampling factors up to a size of only 13x13. © 2015 IEEE.
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| 8. |
- Alonso-Fernandez, Fernando, 1978-, et al.
(författare)
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Super-Resolution for Selfie Biometrics : Introduction and Application to Face and Iris
- 2019. - 1
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Ingår i: Selfie Biometrics. - Cham : Springer. - 9783030269715 - 9783030269722 ; , s. 105-128
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Bokkapitel (refereegranskat)abstract
- Biometric research is heading towards enabling more relaxed acquisition conditions. This has effects on the quality and resolution of acquired images, severly affecting the accuracy of recognition systems if not tackled appropriately. In this chapter, we give an overview of recent research in super-resolution reconstruction applied to biometrics, with a focus on face and iris images in the visible spectrum, two prevalent modalities in selfie biometrics. After an introduction to the generic topic of super-resolution, we investigate methods adapted to cater for the particularities of these two modalities. By experiments, we show the benefits of incorporating super-resolution to improve the quality of biometric images prior to recognition. © Springer Nature AG 2019
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| 9. |
- Beaton, Dorcas E, et al.
(författare)
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OMERACT Filter Evidence Supporting the Measurement of At-work Productivity Loss as an Outcome Measure in Rheumatology Research.
- 2016
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Ingår i: Journal of Rheumatology. - : The Journal of Rheumatology. - 0315-162X .- 1499-2752. ; 43:1, s. 214-222
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Tidskriftsartikel (refereegranskat)abstract
- Indicators of work role functioning (being at work, and being productive while at work) are important outcomes for persons with arthritis. As the worker productivity working group at OMERACT (Outcome Measures in Rheumatology), we sought to provide an evidence base for consensus on standardized instruments to measure worker productivity [both absenteeism and at-work productivity (presenteeism) as well as critical contextual factors].
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| 10. |
- Lundgren Nilsson, Åsa, 1965, et al.
(författare)
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Patient-reported outcome measures in osteoarthritis : a systematic search and review of their use and psychometric properties.
- 2018
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Ingår i: RMD Open. - : BMJ. - 2056-5933. ; 4:2
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Tidskriftsartikel (refereegranskat)abstract
- Introduction: Patient-reported outcome measures (PROM) or self-completed questionnaires have been used to report outcomes in osteoarthritis (OA) for over 35 years. Choices will always need to be made about what should be measured and, if relevant, what would be the most appropriate PROM to use. The current study aims to describe the available PROMs used in OA and their performance quality, so that informed choices can be made about the most appropriate PROM for a particular task.Methods: The study included a systematic search for PROMs that have been in use over 17 years (period 2000-2016), and to catalogue their psychometric properties, and to present the evidence in a user-friendly fashion.Results: 78 PROMs were identified with psychometric evidence available. The domains of pain, self-care, mobility and work dominated, whereas domains such as cleaning and laundry and leisure, together with psychological and contextual factors, were poorly served. The most frequently used PROMs included the Western Ontario McMaster Osteoarthritis Index, the Short Form 36 and the Knee Disability and Osteoarthritis Outcome Score which, between them, appeared in more than 4000 papers. Most domains had at least one PROM with the highest level of psychometric evidence.Conclusion: A broad range of PROMs are available for measuring OA outcomes. Some have good psychometric evidence, others not so. Some important psychological areas such as self-efficacy were poorly served. The study provides a current baseline for what is available, and identifies the shortfall in key domains if the full biopsychosocial model is to be explored.
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