| 1. |
- Beal, Jacob, et al.
(författare)
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Robust estimation of bacterial cell count from optical density
- 2020
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Ingår i: Communications Biology. - : Springer Science and Business Media LLC. - 2399-3642. ; 3:1
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Tidskriftsartikel (refereegranskat)abstract
- Optical density (OD) is widely used to estimate the density of cells in liquid culture, but cannot be compared between instruments without a standardized calibration protocol and is challenging to relate to actual cell count. We address this with an interlaboratory study comparing three simple, low-cost, and highly accessible OD calibration protocols across 244 laboratories, applied to eight strains of constitutive GFP-expressing E. coli. Based on our results, we recommend calibrating OD to estimated cell count using serial dilution of silica microspheres, which produces highly precise calibration (95.5% of residuals <1.2-fold), is easily assessed for quality control, also assesses instrument effective linear range, and can be combined with fluorescence calibration to obtain units of Molecules of Equivalent Fluorescein (MEFL) per cell, allowing direct comparison and data fusion with flow cytometry measurements: in our study, fluorescence per cell measurements showed only a 1.07-fold mean difference between plate reader and flow cytometry data.
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| 2. |
- Bousquet, Jean, et al.
(författare)
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ARIA digital anamorphosis : Digital transformation of health and care in airway diseases from research to practice
- 2021
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Ingår i: Allergy. European Journal of Allergy and Clinical Immunology. - : John Wiley & Sons. - 0105-4538 .- 1398-9995. ; 76:1, s. 168-190
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Forskningsöversikt (refereegranskat)abstract
- Digital anamorphosis is used to define a distorted image of health and care that may be viewed correctly using digital tools and strategies. MASK digital anamorphosis represents the process used by MASK to develop the digital transformation of health and care in rhinitis. It strengthens the ARIA change management strategy in the prevention and management of airway disease. The MASK strategy is based on validated digital tools. Using the MASK digital tool and the CARAT online enhanced clinical framework, solutions for practical steps of digital enhancement of care are proposed.
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| 3. |
- de Vries, Paul S., et al.
(författare)
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Comparison of HapMap and 1000 Genomes Reference Panels in a Large-Scale Genome-Wide Association Study
- 2017
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Ingår i: PLOS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 12:1
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Tidskriftsartikel (refereegranskat)abstract
- An increasing number of genome-wide association (GWA) studies are now using the higher resolution 1000 Genomes Project reference panel (1000G) for imputation, with the expectation that 1000G imputation will lead to the discovery of additional associated loci when compared to HapMap imputation. In order to assess the improvement of 1000G over HapMap imputation in identifying associated loci, we compared the results of GWA studies of circulating fibrinogen based on the two reference panels. Using both HapMap and 1000G imputation we performed a meta-analysis of 22 studies comprising the same 91,953 individuals. We identified six additional signals using 1000G imputation, while 29 loci were associated using both HapMap and 1000G imputation. One locus identified using HapMap imputation was not significant using 1000G imputation. The genome-wide significance threshold of 5x10(-8) is based on the number of independent statistical tests using HapMap imputation, and 1000G imputation may lead to further independent tests that should be corrected for. When using a stricter Bonferroni correction for the 1000G GWA study (P-value < 2.5x10(-8)), the number of loci significant only using HapMap imputation increased to 4 while the number of loci significant only using 1000G decreased to 5. In conclusion, 1000G imputation enabled the identification of 20% more loci than HapMap imputation, although the advantage of 1000G imputation became less clear when a stricter Bonferroni correction was used. More generally, our results provide insights that are applicable to the implementation of other dense reference panels that are under development.
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| 4. |
- de Vries, Arjen E., et al.
(författare)
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Perceived barriers of heart failure nurses and cardiologists in using clinical decision support systems in the treatment of heart failure patients
- 2013
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Ingår i: BMC Medical Informatics and Decision Making. - : BioMed Central. - 1472-6947. ; 13:54
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Tidskriftsartikel (refereegranskat)abstract
- BackgroundClinical Decision Support Systems (CDSSs) can support guideline adherence in heart failure (HF) patients. However, the use of CDSSs is limited and barriers in working with CDSSs have been described as a major obstacle. It is unknown if barriers to CDSSs are present and differ between HF nurses and cardiologists. Therefore the aims of this study are; 1. Explore the type and number of perceived barriers of HF nurses and cardiologists to use a CDSS in the treatment of HF patients. 2. Explore possible differences in perceived barriers between two groups. 3. Assess the relevance and influence of knowledge management (KM) on Responsibility/Trust (R&T) and Barriers/Threats (B&T).MethodsA questionnaire was developed including; B&T, R&T, and KM. For analyses, descriptive techniques, 2-tailed Pearson correlation tests, and multiple regression analyses were performed.ResultsThe response- rate of 220 questionnaires was 74%. Barriers were found for cardiologists and HF nurses in all the constructs. Sixty-five percent did not want to be dependent on a CDSS. Nevertheless thirty-six percent of HF nurses and 50% of cardiologists stated that a CDSS can optimize HF medication. No relationship between constructs and age; gender; years of work experience; general computer experience and email/internet were observed. In the group of HF nurses a positive correlation (r .33, P<.01) between years of using the internet and R&T was found. In both groups KM was associated with the constructs B&T (B=.55, P=<.01) and R&T (B=.50, P=<.01).ConclusionsBoth cardiologists and HF-nurses perceived barriers in working with a CDSS in all of the examined constructs. KM has a strong positive correlation with perceived barriers, indicating that increasing knowledge about CDSSs can decrease their barriers.
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| 5. |
- Okada, Yukinori, et al.
(författare)
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Genetics of rheumatoid arthritis contributes to biology and drug discovery
- 2014
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Ingår i: Nature. - : Nature Publishing Group. - 0028-0836 .- 1476-4687. ; 506:7488, s. 376-381
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Tidskriftsartikel (refereegranskat)abstract
- A major challenge in human genetics is to devise a systematic strategy to integrate disease-associated variants with diverse genomic and biological data sets to provide insight into disease pathogenesis and guide drug discovery for complex traits such as rheumatoid arthritis (RA)(1). Here we performed a genome-wide association study meta-analysis in a total of >100,000 subjects of European and Asian ancestries (29,880 RA cases and 73,758 controls), by evaluating similar to 10 million single-nucleotide polymorphisms. We discovered 42 novel RA risk loci at a genome-wide level of significance, bringing the total to 101 (refs 2-4). We devised an in silico pipeline using established bioinformatics methods based on functional annotation(5), cis-acting expression quantitative trait loci(6) and pathway analyses(7-9)-as well as novel methods based on genetic overlap with human primary immunodeficiency, haematological cancer somatic mutations and knockout mouse phenotypes-to identify 98 biological candidate genes at these 101 risk loci. We demonstrate that these genes are the targets of approved therapies for RA, and further suggest that drugs approved for other indications may be repurposed for the treatment of RA. Together, this comprehensive genetic study sheds light on fundamental genes, pathways and cell types that contribute to RA pathogenesis, and provides empirical evidence that the genetics of RA can provide important information for drug discovery.
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| 6. |
- de Vries, Arjen E, et al.
(författare)
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Follow-up and treatment of an instable patient with heart failure using telemonitoring and a computerised disease management system : A case report
- 2012
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Ingår i: European Journal of Cardiovascular Nursing. - London, UK : Sage Publications. - 1474-5151 .- 1873-1953. ; 11:4, s. 432-438
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Tidskriftsartikel (refereegranskat)abstract
- In the last decades, the introduction of information and communication technology (ICT) in healthcare promised an improved quality of care while reducing workload and improving cost-effectiveness. This might be realised by the use of computer guided decision support systems and telemonitoring. This case study describes the process of care of a patient with chronic heart failure, who was treated with a computerised disease management system in combination with telemonitoring. With the help of these appliances, we think we were probably able to prevent at least two readmissions for heart failure in a period of 10months. We also gained more insight into patient's behaviour with regards to compliance with the heart failure regimen at home. Frequent contact at distance and the online availability of physiological measurements at home facilitated patient tailored education and helped the patient to react adequately to symptoms of deterioration. Additionally, up-titration of heart failure medication was performed without contacting the patient at the outpatient clinic.
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| 7. |
- de Vries, Arjen E., et al.
(författare)
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Health Professionals Expectations Versus Experiences of Internet-Based Telemonitoring: Survey Among Heart Failure Clinics
- 2013
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Ingår i: Journal of Medical Internet Research. - : Journal of Medical Internet Research / Gunther Eysenbach. - 1438-8871. ; 15:1, s. 73-83
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Tidskriftsartikel (refereegranskat)abstract
- Background: Although telemonitoring is increasingly used in heart failure care, data on expectations, experiences, and organizational implications concerning telemonitoring are rarely addressed, and the optimal profile of patients who can benefit from telemonitoring has yet to be defined. less thanbrgreater than less thanbrgreater thanObjective: To assess the actual status of use of telemonitoring and to describe the expectations, experiences, and organizational aspects involved in working with telemonitoring in heart failure in the Netherlands. less thanbrgreater than less thanbrgreater thanMethods: In collaboration with the Netherlands Organization for Applied Scientific Research (TNO), a 19-item survey was sent to all outpatient heart failure clinics in the Netherlands, addressed to cardiologists and heart failure nurses working in the clinics. less thanbrgreater than less thanbrgreater thanResults: Of the 109 heart failure clinics who received a survey, 86 clinics responded (79%). In total, 31 out of 86 (36%) heart failure clinics were using telemonitoring and 12 heart failure clinics (14%) planned to use telemonitoring within one year. The number of heart failure patients receiving telemonitoring generally varied between 10 and 50; although in two clinics more than 75 patients used telemonitoring. The main goals for using telemonitoring are "monitoring physical condition", "monitoring signs of deterioration" (n=39, 91%), "monitoring treatment" (n=32, 74%), "adjusting medication" (n=24, 56%), and "educating patients" (n=33, 77%). Most patients using telemonitoring were in the New York Heart Association (NYHA) functional classes II (n=19, 61%) and III (n=27, 87%) and were offered the use of the telemonitoring system "as long as needed" or without a time limit. However, the expectations of the use of telemonitoring were not met after implementation. Eight of the 11 items about expectations versus experiences were significantly decreased (Pandlt;.001). Health care professionals experienced the most changes related to the use of telemonitoring in their work, in particular with respect to "keeping up with current development" (before 7.2, after 6.8, P=.15), "being innovative" (before 7.0, after 6.1, P=.003), and "better guideline adherence" (before 6.3, after 5.3, P=.005). Strikingly, 20 out of 31 heart failure clinics stated that they were considering using a different telemonitoring system than the system used at the time. less thanbrgreater than less thanbrgreater thanConclusions: One third of all heart failure clinics surveyed were using telemonitoring as part of their care without any transparent, predefined criteria of user requirements. Prior expectations of telemonitoring were not reflected in actual experiences, possibly leading to disappointment. (J Med Internet Res 2013;15(1):e4) doi:10.2196/jmir.2161
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| 8. |
- de Vries, Arjen E, et al.
(författare)
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The value of INnovative ICT guided disease management combined with Telemonitoring in OUtpatient clinics for Chronic Heart failure patients. Design and methodology of the IN TOUCH study : a multicenter randomised trial
- 2011
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Ingår i: BMC health services research. - : Springer Science and Business Media LLC. - 1472-6963. ; 11, s. 167-
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Although the value of telemonitoring in heart failure patients is increasingly studied, little is known about the value of the separate components of telehealth: ICT guided disease management and telemonitoring. The aim of this study is to investigate the value of telemonitoring added to ICT guided disease management (DM) on the quality and efficiency of care in patients with chronic heart failure (CHF) after a hospitalisation.METHODS/DESIGN: The study is divided in two arms; a control arm (DM) and an intervention arm (DM+TM) in 10 hospitals in the Netherlands. In total 220 patients will be included after worsening of CHF (DM: N = 90, DM+TM: N = 130). Total follow-up will be 9 months. Data will be collected at inclusion and then after 2 weeks, 4.5 and 9 months. The primary endpoint of this study is a composite score of: 1: death from any cause during the follow-up of the study, 2: first readmission for HF and 3: change in quality of life compared to baseline, assessed by the Minnesota Living with Heart failure Questionnaire. The study has started in December 2009 and results are expected in 2012.CONCLUSIONS: The IN TOUCH study is the first to investigate the effect of telemonitoring on top of ICT guided DM on the quality and efficiency of care in patients with worsening HF and will use a composite score as its primary endpoint.TRIAL REGISTRATION: Netherlands Trial Register (NTR): NTR1898.
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| 9. |
- Kraai, Imke, et al.
(författare)
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The value of telemonitoring and ICT-guided disease management in heart failure: Results from the IN TOUCH study
- 2016
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Ingår i: International Journal of Medical Informatics. - : ELSEVIER IRELAND LTD. - 1386-5056 .- 1872-8243. ; 85:1, s. 53-60
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Tidskriftsartikel (refereegranskat)abstract
- Aim: It is still unclear whether telemonitoring reduces hospitalization and mortality in heart failure (HF) patients and whether adding an Information and Computing Technology-guided-disease-management-system (ICT-guided-DMS) improves clinical and patient reported outcomes or reduces healthcare costs. Methods: A multicenter randomized controlled trial was performed testing the effects of INnovative ICT-guided-DMS combined with Telemonitoring in OUtpatient clinics for Chronic HF patients (IN TOUCH) with in total 179 patients (mean age 69 years; 72% male; 77% in New York Heart Association Classification (NYHA) III-IV; mean left ventricular ejection fraction was 28%). Patients were randomized to ICT-guided-DMS or to ICT-guided-DMS + telemonitoring with a follow-up of nine months. The composite endpoint included mortality, HF-readmission and change in health-related quality of life (HR-QoL). Results: In total 177 patients were eligible for analyses. The mean score of the primary composite endpoint was -0.63 in ICT-guided-DMS vs. -0.73 in ICT-guided-DMS + telemonitoring (mean difference 0.1,95% CI: -0.67 +0.82, p = 0.39). All-cause mortality in ICT-guided-DMS was 12% versus 15% in ICT-guided-DMS + telemonitoring (p = 0.27); HF-readmission 28% vs. 27% p = 0.87; all-cause readmission was 49% vs. 51% (p = 0.78). HR-QoL improved in most patients and was equal in both groups. Incremental costs were 1360 in favor of ICT-guided-DMS. ICT-guided-DMS + telemonitoring had significantly fewer HF-outpatient-clinic visits (p < 0.01). Conclusion: ICT-guided-DMS + telemonitoring for the management of HF patients did not affect the primary and secondary endpoints. However, we did find a reduction in visits to the HF-outpatient clinic in this group suggesting that telemonitoring might be safe to use in reorganizing HF-care with relatively low costs. (C) 2015 The Authors. Published by Elsevier Ireland Ltd. This is an open access article under the CC BY-NC-ND license (http://cleativecommons.org/licenses/by-nc-nd/4.0/).
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| 10. |
- Cataldi, Gianni, et al.
(författare)
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ALMA Resolves CI Emission from the beta Pictoris Debris Disk
- 2018
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Ingår i: Astrophysical Journal. - : American Astronomical Society. - 0004-637X .- 1538-4357. ; 861:1
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Tidskriftsartikel (refereegranskat)abstract
- The debris disk around beta Pictoris is known to contain gas. Previous ALMA observations revealed a CO belt at similar to 85 au with a distinct clump, interpreted as a location of enhanced gas production. Photodissociation converts CO into C and O within similar to 50 a. We resolve C I emission at 492 GHz using ALMA and study its spatial distribution. C I shows the same clump as seen for CO. This is surprising, as C is expected to quickly spread in azimuth. We derive a low C mass (between 5 x 10(-4) and 3.1 x 10(-3) MA(circle plus)), indicating that gas production started only recently (within similar to 5000 a). No evidence is seen for an atomic accretion disk inward of the CO belt, perhaps because the gas did not yet have time to spread radially. The fact that C and CO share the same asymmetry argues against a previously proposed scenario where the clump is due to an outward-migrating planet trapping planetesimals in a resonance, nor can the observations be explained by an eccentric planetesimal belt secularly forced by a planet. Instead, we suggest that the dust and gas disks should be eccentric. Such a configuration, we further speculate, might be produced by a recent tidal disruption event. Assuming that the disrupted body has had a CO mass fraction of 10%, its total mass would be greater than or similar to 3M(Moon).
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| 11. |
- Charrier, Dimitri S. H., et al.
(författare)
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Real versus measured surface potentials in scanning Kelvin probe microscopy
- 2008
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Ingår i: ACS Nano. - : American Chemical Society. - 1936-0851 .- 1936-086X. ; 2:4, s. 622-626
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Tidskriftsartikel (refereegranskat)abstract
- Noncontact potentiometry or scanning Kelvin probe microscopy (SKPM) is a widely used technique to study charge injection and transport in (in)organic devices by measuring a laterally resolved local potential. This technique suffers from the significant drawback that experimentally obtained curves do not generally reflect the true potential profile in the device due to nonlocal coupling between the probing tip and the device. In this work, we quantitatively explain the experimental SKPM response and by doing so directly link theoretical device models to real observables. In particular, the model quantitatively explains the effects of the tip-sample distance and the dependence on the orientation of the probing tip with respect to the device.
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| 12. |
- Chr Germs, Wijnand, et al.
(författare)
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High-efficiency dielectrophoretic ratchet
- 2012
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Ingår i: Physical Review E. Statistical, Nonlinear, and Soft Matter Physics. - : American Physical Society. - 1539-3755 .- 1550-2376. ; 86:4
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Tidskriftsartikel (refereegranskat)abstract
- Brownian ratchets enable the use of thermal motion in performing useful work. They typically employ spatial asymmetry to rectify nondirected external forces that drive the system out of equilibrium (cf. running marbles on a shaking washboard). The major application foreseen for Brownian ratchets is high-selectivity fractionation of particle or molecule distributions. Here, we investigate the functioning of an important model system, the on/off ratchet forwater-suspended particles, in which interdigitated finger electrodes can be switched on and off to create a time-dependent, spatially periodic but asymmetric potential. Surprisingly, we find that mainly dielectrophoretic rather than electrophoretic forces are responsible for the ratchet effect. This has major implications for the (a) symmetry of the ratchet potential and the settings needed for optimal performance. We demonstrate that by applying a potential offset the ratchet can be optimized such that its particle displacement efficiency reaches the theoretical upper limit corresponding to the electrode geometry and particle size. Efficient fractionation based on size selectivity is therefore not only possible for charged species, but also for uncharged ones, which greatly expands the applicability range of this type of Brownian ratchet.
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| 13. |
- Dalaei, Farima, et al.
(författare)
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Body Contouring Surgery after Bariatric Surgery Improves Long-Term Health-Related Quality of Life and Satisfaction with Appearance : An International Longitudinal Cohort Study Using the BODY-Q
- 2024
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Ingår i: Annals of Surgery. - 0003-4932. ; 279:6, s. 1008-1017
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Tidskriftsartikel (refereegranskat)abstract
- Objective: To examine health-related quality of life (HRQL) and satisfaction with appearance in patients who have undergone bariatric surgery (BS) with or without subsequent body contouring surgery (BCS) in relation to the general population normative for the BODY-Q. Background: The long-term impact of BS with or without BCS has not been established using rigorously developed and validated patient-reported outcome measures. The BODY-Q is a patient-reported outcome measure developed to measure changes in HRQL and satisfaction with appearance in patients with BS and BCS. Methods: Prospective BODY-Q data were collected from 6 European countries (Denmark, the Netherlands, Finland, Germany, Italy, and Poland) from June 2015 to February 2022 in a cohort of patients who underwent BS. Mixed-effects regression models were used to analyze changes in HRQL and appearance over time between patients who did and did not receive BCS and to examine the impact of patient-level covariates on outcomes. Results: This study included 24,604 assessments from 5620 patients. BS initially led to improved HRQL and appearance scores throughout the first postbariatric year, followed by a gradual decrease. Patients who underwent subsequent BCS after BS experienced a sustained improvement in HRQL and appearance or remained relatively stable for up to 10 years postoperatively. Conclusions: Patients who underwent BCS maintained an improvement in HRQL and satisfaction with appearance in contrast to patients who only underwent BS, who reported a decline in scores 1 to 2 years postoperatively. Our results emphasize the pivotal role that BCS plays in the completion of the weight loss trajectory.
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| 14. |
- de Vries, B. L., et al.
(författare)
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Comet-like mineralogy of olivine crystals in an extrasolar proto-Kuiper belt
- 2012
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Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 490:7418, s. 74-76
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Tidskriftsartikel (refereegranskat)abstract
- Some planetary systems harbour debris disks containing planetesimals such as asteroids and comets(1). Collisions between such bodies produce small dust particles(2), the spectral features of which reveal their composition and, hence, that of their parent bodies. A measurement of the composition of olivine crystals (Mg2-2xFe2xSiO4) has been done for the protoplanetary disk HD 100546 (refs 3, 4) and for olivine crystals in the warm inner parts of planetary systems. The latter compares well with the iron-rich olivine in asteroids(5,6) (x approximate to 0.29). In the cold outskirts of the beta Pictoris system, an analogue to the young Solar System, olivine crystals were detected(7) but their composition remained undetermined, leaving unknown how the composition of the bulk of Solar System cometary olivine grains compares with that of extrasolar comets(8,9). Here we report the detection of the 69-micrometre-wavelength band of olivine crystals in the spectrum of beta Pictoris. Because the disk is optically thin, we can associate the crystals with an extrasolar proto-Kuiper belt a distance of 15-45 astronomical units from the star (one astronomical unit is the Sun-Earth distance), determine their magnesium-rich composition (x = 0.01 +/- 0.001) and show that they make up 3.6 +/- 1.0 per cent of the total dust mass. These values are strikingly similar to those for the dust emitted by the most primitive comets in the Solar System(8-10), even though beta Pictoris is more massive and more luminous and has a different planetary system architecture.
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| 15. |
- Edvinsson, Lars, et al.
(författare)
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Effect of the calcitonin gene-related peptide (CGRP) receptor antagonist telcagepant in human cranial arteries.
- 2010
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Ingår i: Cephalalgia. - : SAGE Publications. - 0333-1024 .- 1468-2982. ; 30:10, s. 1233-1240
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Tidskriftsartikel (refereegranskat)abstract
- INTRODUCTION: Calcitonin gene-related peptide (CGRP) is a neuronal messenger in intracranial sensory nerves and is considered to play a significant role in migraine pathophysiology. MATERIALS AND METHODS: We investigated the effect of the CGRP receptor antagonist, telcagepant, on CGRP-induced cranial vasodilatation in human isolated cerebral and middle meningeal arteries. We also studied the expression of the CGRP receptor components in cranial arteries with immunocytochemistry. Concentration response curves to αCGRP were performed in human isolated cerebral and middle meningeal arteries in the absence or presence of telcagepant. Arterial slices were stained for RAMP1, CLR and actin in a double immunofluorescence staining. RESULTS: In both arteries, we found that: (i) telcagepant was devoid of any contractile or relaxant effects per se; (ii) pretreatment with telcagepant antagonised the αCGRP-induced relaxation in a competitive manner; and (iii) immunohistochemistry revealed expression and co-localisation of CLR and RAMP1 in the smooth muscle cells in the media layer of both arteries. CONCLUSIONS: Our findings provide morphological and functional data on the presence of CGRP receptors in cerebral and meningeal arteries, which illustrates a possible site of action of telcagepant in the treatment of migraine.
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| 16. |
- Greaves, J. S., et al.
(författare)
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Extreme Conditions in a Close Analog to the Young Solar System: Herschel Observations of ∈ Eridani
- 2014
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Ingår i: Astrophysical Journal Letters. - : American Astronomical Society. - 2041-8213 .- 2041-8205. ; 791:1
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Tidskriftsartikel (refereegranskat)abstract
- Far-infrared Herschel images of the is an element of Eridani system, seen at a fifth of the Sun's present age, resolve two belts of debris emission. Fits to the 160 mu m PACS image yield radial spans for these belts of 12-16 and 54-68 AU. The south end of the outer belt is approximate to 10% brighter than the north end in the PACS+SPIRE images at 160, 250, and 350 mu m, indicating a pericenter glow attributable to a planet "c" From this asymmetry and an upper bound on the offset of the belt center, this second planet should be mildly eccentric (e(c) approximate to 0.03-0.3). Compared to the asteroid and Kuiper Belts of the young Sun, the is an element of Eri belts are intermediate in brightness and more similar to each other, with up to 20 km sized collisional fragments in the inner belt totaling approximate to 5% of an Earth mass. This reservoir may feed the hot dust close to the star and could send many impactors through the Habitable Zone, especially if it is being perturbed by the suspected planet is an element of Eri b, at semi-major axis approximate to 3 AU.
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| 17. |
- Liseau, René, 1949, et al.
(författare)
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Gas and dust in the star-forming region ρ Oph A ∗, ∗∗, ∗∗∗: The dust opacity exponent β and the gas-to-dust mass ratio g2d
- 2015
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 578
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Tidskriftsartikel (refereegranskat)abstract
- © ESO, 2015. Aims. We aim at determining the spatial distribution of the gas and dust in star-forming regions and address their relative abundances in quantitative terms. We also examine the dust opacity exponent β for spatial and/or temporal variations. Methods. Using mapping observations of the very dense ρ Oph A core, we examined standard 1D and non-standard 3D methods to analyse data of far-infrared and submillimetre (submm) continuum radiation. The resulting dust surface density distribution can be compared to that of the gas. The latter was derived from the analysis of accompanying molecular line emission, observed with Herschel from space and with APEX from the ground. As a gas tracer we used N2H+, which is believed to be much less sensitive to freeze-out than CO and its isotopologues. Radiative transfer modelling of the N2H+ (J = 3-2) and (J = 6-5) lines with their hyperfine structure explicitly taken into account provides solutions for the spatial distribution of the column density N(H2), hence the surface density distribution of the gas. Results. The gas-to-dust mass ratio is varying across the map, with very low values in the central regions around the core SM 1. The global average, = 88, is not far from the canonical value of 100, however. In ρ Oph A, the exponent β of the power-law description for the dust opacity exhibits a clear dependence on time, with high values of 2 for the envelope-dominated emission in starless Class -1 sources to low values close to 0 for the disk-dominated emission in Class III objects. β assumes intermediate values for evolutionary classes in between. Conclusions. Since β is primarily controlled by grain size, grain growth mostly occurs in circumstellar disks. The spatial segregation of gas and dust, seen in projection toward the core centre, probably implies that, like C18O, also N2H+ is frozen onto the grains.
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| 18. |
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| 19. |
- Roeling, Erik M., et al.
(författare)
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Organic electronic ratchets doing work
- 2011
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Ingår i: Nature Materials. - : Nature Publishing Group. - 1476-1122 .- 1476-4660. ; 10:1, s. 51-55
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Tidskriftsartikel (refereegranskat)abstract
- The possibility to extract work from periodic, undirected forces has intrigued scientists for over a century-in particular, the rectification of undirected motion of particles by ratchet potentials, which are periodic but asymmetric functions. Introduced by Smoluchowski and Feynman(1,2) to study the (dis)ability to generate motion from an equilibrium situation, ratchets operate out of equilibrium, where the second law of thermodynamics no longer applies. Although ratchet systems have been both identified in nature(3,4) and used in the laboratory for the directed motion of microscopic objects(5-9), electronic ratchets(10-13) have been of limited use, as they typically operate at cryogenic temperatures and generate subnanoampere currents and submillivolt voltages(10-14). Here, we present organic electronic ratchets that operate up to radio frequencies at room temperature and generate currents and voltages that are orders of magnitude larger. This enables their use as a d.c. power source. We integrated the ratchets into logic circuits, in which they act as the d.c. equivalent of the a. c. transformer, and generate enough power to drive the circuitry. Our findings show that electronic ratchets may be of actual use.
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| 20. |
- Roeling, Erik M., et al.
(författare)
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Scaling of characteristic frequencies of organic electronic ratchets
- 2012
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - : American Physical Society. - 1098-0121 .- 1550-235X. ; 85:4
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Tidskriftsartikel (refereegranskat)abstract
- The scaling of the characteristic frequencies of electronic ratchets operating in a flashing mode is investigated by measurements and numerical simulations. The ratchets are based on organic field effect transistors operated in accumulation mode. Oscillating potentials applied to asymmetrically spaced interdigitated finger electrodes embedded in the gate dielectric create a time-dependent, spatially asymmetric perturbation of the transistor channel potential. As a result, a net dc current can flow between source and drain despite zero source-drain bias. The frequency at current maximum is linearly dependent on the charge carrier density and the charge carrier mobility and inversely proportional to the squared length of the ratchet period, which can be related to the RC time of one asymmetric unit. Counterintuitively, it is independent of driving amplitude. Furthermore, the frequency at current maximum depends on the asymmetry of the ratchet potential, whereas the frequency of maximum charge pumping efficiency does not.
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| 21. |
- Roeling, Erik M., et al.
(författare)
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The performance of organic electronic ratchets
- 2012
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Ingår i: AIP Advances. - : American Institute of Physics (AIP): Open Access Journals / AIP Publishing LLC. - 2158-3226. ; 2:1
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Tidskriftsartikel (refereegranskat)abstract
- Organic electronic ratchets rectify time-correlated external driving forces, giving output powers that can drive electronic circuitry. In this work their performance characteristics are investigated using numerical modeling and measurements. It is shown how the characteristic parameters of the time-varying asymmetric potential like length scales and amplitude, as well as the density and mobility of the charge carriers in the device influence the performance characteristics. Various ratchet efficiencies and their relations are discussed. With all settings close to optimum, a ratchet with charge displacement and power efficiencies close to 50% and 7% respectively is obtained. Copyright 2012 Author(s). This article is distributed under a Creative Commons Attribution 3.0 Unported License. [doi:10.1063/1.3677934]
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| 22. |
- Van Loon, Anne F., et al.
(författare)
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Review article: Drought as a continuum: memory effects in interlinked hydrological, ecological, and social systems
- 2024
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Droughts are often long lasting phenomena, without a distinct start or end, and with impacts cascading across sectors and systems, creating long-term legacies. Nevertheless, our current perception and management of droughts and their impacts is often event-based, which can limit the effective assessment of drought risks and reduction of drought impacts. Here, we advocate for changing this perspective and viewing drought as a hydro-eco-social continuum. We take a systems theory perspective and focus on how “memory” causes feedback and interactions between parts of the interconnected systems at different time scales. We first discuss the characteristics of the drought continuum with a focus on the hydrological, ecological, and social systems separately; and then study the system of systems. Our analysis is based on a review of the literature and a study of five cases: Chile, the Colorado River Basin in the US, Northeast Brazil, Kenya, and the Rhine River Basin in Northwest Europe. We find that the memories of past dry and wet periods, carried by both bio-physical (e.g. groundwater, vegetation) and social systems (e.g. people, governance), influence how future drought risk manifests. We identify four archetypes of drought dynamics: Impact & recovery; Slow resilience-building; Gradual collapse; and High resilience, big shock. The interactions between the hydrological, ecological and social systems result in systems shifting between these types, which plays out differently in the five case studies. We call for more research on drought preconditions and recovery in different systems, on dynamics cascading between systems and triggering system changes, and on dynamic vulnerability and maladaptation. Additionally, we argue for more continuous monitoring of drought hazards and impacts, modelling tools that better incorporate memories and adaptation responses, and management strategies that increase social and institutional memory to better deal with the complex hydro-eco-social drought continuum and identify effective pathways to adaptation.
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