| 1. |
- Klionsky, Daniel J., et al.
(författare)
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Guidelines for the use and interpretation of assays for monitoring autophagy
- 2012
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Ingår i: Autophagy. - : Informa UK Limited. - 1554-8635 .- 1554-8627. ; 8:4, s. 445-544
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Forskningsöversikt (refereegranskat)abstract
- In 2008 we published the first set of guidelines for standardizing research in autophagy. Since then, research on this topic has continued to accelerate, and many new scientists have entered the field. Our knowledge base and relevant new technologies have also been expanding. Accordingly, it is important to update these guidelines for monitoring autophagy in different organisms. Various reviews have described the range of assays that have been used for this purpose. Nevertheless, there continues to be confusion regarding acceptable methods to measure autophagy, especially in multicellular eukaryotes. A key point that needs to be emphasized is that there is a difference between measurements that monitor the numbers or volume of autophagic elements (e.g., autophagosomes or autolysosomes) at any stage of the autophagic process vs. those that measure flux through the autophagy pathway (i.e., the complete process); thus, a block in macroautophagy that results in autophagosome accumulation needs to be differentiated from stimuli that result in increased autophagic activity, defined as increased autophagy induction coupled with increased delivery to, and degradation within, lysosomes (in most higher eukaryotes and some protists such as Dictyostelium) or the vacuole (in plants and fungi). In other words, it is especially important that investigators new to the field understand that the appearance of more autophagosomes does not necessarily equate with more autophagy. In fact, in many cases, autophagosomes accumulate because of a block in trafficking to lysosomes without a concomitant change in autophagosome biogenesis, whereas an increase in autolysosomes may reflect a reduction in degradative activity. Here, we present a set of guidelines for the selection and interpretation of methods for use by investigators who aim to examine macroautophagy and related processes, as well as for reviewers who need to provide realistic and reasonable critiques of papers that are focused on these processes. These guidelines are not meant to be a formulaic set of rules, because the appropriate assays depend in part on the question being asked and the system being used. In addition, we emphasize that no individual assay is guaranteed to be the most appropriate one in every situation, and we strongly recommend the use of multiple assays to monitor autophagy. In these guidelines, we consider these various methods of assessing autophagy and what information can, or cannot, be obtained from them. Finally, by discussing the merits and limits of particular autophagy assays, we hope to encourage technical innovation in the field.
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| 2. |
- Abrahamsson, Per, 1985, et al.
(författare)
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An infield study of road snow properties related to snow-car adhesion and snow smoke
- 2018
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Ingår i: Cold Regions Science and Technology. - : Elsevier BV. - 0165-232X. ; 145, s. 32-39
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Tidskriftsartikel (refereegranskat)abstract
- © 2017 Elsevier B.V. This article analyzes the properties of snow on the road related to the formation of snow smoke and contamination of the car. The increased usage of sensors for active safety in modern cars increases the importance of understanding contamination of the car body. The analysis characterizes snow in terms of shape, size, and adhesiveness. The data is related to changing weather conditions and experienced car contamination. Several different sampling positions were chosen both on the road and on the car. The temperatures during the days of measurements ranged from − 4 °C to − 12 °C, which gave cold and dry snow. Data on size and shape was obtained via microscope analysis. An infield adhesion tester for snow adhesion measurements was built. The microscope analysis showed that the shape of the snow particles in the tire tracks and on the car body generally had a rounded structure. Even soon after a fresh snow fall, the rounded shapes remained in these positions. This structure was found to change to a more edgy hexagonal shape during hoar formation on the existing snow. The particle size distributions from tire tracks, from suspended snow smoke, and from different positions on the car were analyzed. It was found that smaller particles travel higher and are more prone to enter the wake behind the car to stick to the back parts of the vehicle. The adhesion test gave little distinction between the different snow types and samples. The adhesion force was found to range from 2 to 12 dyne.
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| 3. |
- Bausch, Birke, et al.
(författare)
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Clinical Characterization of the Pheochromocytoma and Paraganglioma Susceptibility Genes SDHA, TMEM127, MAX, and SDHAF2 for Gene-Informed Prevention
- 2017
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Ingår i: JAMA Oncology. - : AMER MEDICAL ASSOC. - 2374-2437 .- 2374-2445. ; 3:9, s. 1204-1212
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Tidskriftsartikel (refereegranskat)abstract
- IMPORTANCE Effective cancer prevention is based on accurate molecular diagnosis and results of genetic family screening, genotype-informed risk assessment, and tailored strategies for early diagnosis. The expanding etiology for hereditary pheochromocytomas and paragangliomas has recently included SDHA, TMEM127, MAX, and SDHAF2 as susceptibility genes. Clinical management guidelines for patients with germline mutations in these 4 newly included genes are lacking. OBJECTIVE To study the clinical spectra and age-related penetrance of individuals with mutations in the SDHA, TMEM127, MAX, and SDHAF2 genes. DESIGN, SETTING, AND PATIENTS This study analyzed the prospective, longitudinally followed up European-American-Asian Pheochromocytoma-Paraganglioma Registry for prevalence of SDHA, TMEM127, MAX, and SDHAF2 germline mutation carriers from 1993 to 2016. Genetic predictive testing and clinical investigation by imaging from neck to pelvis was offered to mutation-positive registrants and their relatives to clinically characterize the pheochromocytoma/paraganglioma diseases associated with mutations of the 4 new genes. MAIN OUTCOMES AND MEASURES Prevalence and spectra of germline mutations in the SDHA, TMEM127, MAX, and SDHAF2 genes were assessed. The clinical features of SDHA, TMEM127, MAX, and SDHAF2 disease were characterized. RESULTS Of 972 unrelated registrants without mutations in the classic pheochromocytoma- and paraganglioma-associated genes (632 female [65.0%] and 340 male [35.0%]; age range, 8-80; mean [SD] age, 41.0 [13.3] years), 58 (6.0%) carried germline mutations of interest, including 29 SDHA, 20 TMEM127, 8 MAX, and 1 SDHAF2. Fifty-three of 58 patients (91%) had familial, multiple, extra-adrenal, and/or malignant tumors and/or were younger than 40 years. Newly uncovered are 7 of 63 (11%) malignant pheochromocytomas and paragangliomas in SDHA and TMEM127 disease. SDHA disease occurred as early as 8 years of age. Extra-adrenal tumors occurred in 28 mutation carriers (48%) and in 23 of 29 SDHA mutation carriers (79%), particularly with head and neck paraganglioma. MAX disease occurred almost exclusively in the adrenal glands with frequently bilateral tumors. Penetrance in the largest subset, SDHA carriers, was 39% at 40 years of age and is statistically different in index patients (45%) vs mutation-carrying relatives (13%; P amp;lt; .001). CONCLUSIONS AND RELEVANCE The SDHA, TMEM127, MAX, and SDHAF2 genes may contribute to hereditary pheochromocytoma and paraganglioma. Genetic testing is recommended in patients at clinically high risk if the classic genes are mutation negative. Gene-specific prevention and/or early detection requires regular, systematic whole-body investigation.
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| 4. |
- Dejke, Valter, et al.
(författare)
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Development of prototype low-cost qtss™ wearable flexible more enviro-friendly pressure, shear, and friction sensors for dynamic prosthetic fit monitoring
- 2021
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Ingår i: Sensors. - : MDPI AG. - 1424-8220. ; 21:11
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Tidskriftsartikel (refereegranskat)abstract
- There is a current healthcare need for improved prosthetic socket fit provision for the masses using low-cost and simple to manufacture sensors that can measure pressure, shear, and friction. There is also a need to address society’s increasing concerns regarding the environmental impact of electronics and IoT devices. Prototype thin, low-cost, and low-weight pressure, shear, and loss of friction sensors have been developed and assembled for trans-femoral amputees. These flexible and conformable sensors are simple to manufacture and utilize more enviro-friendly novel magnetite-based QTSS™ (Quantum Technology Supersensor™) quantum materials. They have undergone some initial tests on flat and curved surfaces in a pilot amputee trial, which are presented in this paper. These initial findings indicate that the prototype pressure sensor strip is capable of measuring pressure both on flat and curved socket surfaces in a pilot amputee trial. They have also demonstrated that the prototype shear sensor can indicate increasing shear forces, the resultant direction of the shear forces, and loss of friction/slippage events. Further testing, amputee trials, and ongoing optimization is continuing as part of the SocketSense project to assist prosthetic comfort and fit. © 2021 by the authors
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| 5. |
- Eidevåg, Tobias, 1987, et al.
(författare)
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Modeling of dry snow adhesion during normal impact with surfaces
- 2020
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Ingår i: Powder Technology. - : Elsevier BV. - 1873-328X .- 0032-5910. ; 361, s. 1081-1092
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Tidskriftsartikel (refereegranskat)abstract
- Contamination due to dry snow smoke adhesion is an evident danger for sensor blinding on future autonomous driving cars under winter road conditions. This paper examines at what velocities ice particles and agglomerates, representing dry snow, adhere to surfaces of various materials. Contact models for normal direction, tangential sliding, and tangential rolling that account for the adhesive interaction of spherical particles due to Van der Waals forces are used in the study. Three different scenarios of impacts are presented i) single particle impact, ii) small agglomerate impacts, and iii) large agglomerate impacts. It is shown that by increasing the number of particles in an agglomerate, the velocity at which the agglomerate sticks to the impact wall increases, i.e. the agglomerate is more likely to stick to a surface. It is also shown how material properties influence the tendency of dry road snow to adhere to a surface.
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| 6. |
- Eidevåg, Tobias, 1987, et al.
(författare)
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Snow Contamination of Simplified Automotive Bluff Bodies: A Comparison between Wind Tunnel Experiments and Numerical Modeling
- 2022
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Ingår i: SAE Technical Paper Series. - 400 Commonwealth Drive, Warrendale, PA, United States : SAE International. - 2641-9637 .- 0148-7191 .- 2688-3627.
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Konferensbidrag (refereegranskat)abstract
- We describe experiments and numerical modeling of snow surface contamination on two simplified automotive bluff bodies: The Ahmed body and a wedge. The purpose was twofold: 1) To obtain well defined experimental results of snow contamination on simple geometries; 2) To propose a numerical modeling approach for snow contamination. The experiments were performed in a climatic wind tunnel using a snow cannon at −15 °C and the results show that the snow accumulation depends on the aerodynamics of the studied bluff bodies. Snow accumulates on surfaces in proximity to the aerodynamic wakes of the bodies and characteristic snow patterns are obtained on side surfaces. The numerical modeling approach consisted of an aerodynamic setup coupled with Lagrangian particle tracking. Particles were determined to adhere or rebound depending on an adhesion model combined with a resuspension criterion. The adhesion model was based on adhesive-elastic contact theory and the resuspension criterion is derived from the balance between the aerodynamic forces acting on a particle and the critical force for onset of resuspension. The results show that the numerical method can predict certain characteristic snow patterns obtained from the experiments and we also highlight deviations obtained between experimental and simulation results. The simulation results show that the snow accumulation patterns on a bluff body will depend on the smallest ice particles in a snow sample which implies that samples with larger ice particle (for example natural snow) could produce different snow patterns than the fine machine-made snow used in this study.
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| 7. |
- Eng, Matthias, 1983, et al.
(författare)
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Analysis of Particle Cloud Height Dynamics in a Stirred Tank
- 2016
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Ingår i: AICHE Journal. - : Wiley. - 1547-5905 .- 0001-1541. ; 62:1, s. 338-348
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Tidskriftsartikel (refereegranskat)abstract
- Local and temporal variations of the particle cloud formed in a cylindrical mixing vessel were investigated experimentally. Different particle sizes (0.5, 1, and 2 mm) and volumetric concentration up to 20 vol % were evaluated at different impeller speeds. The time-averaged cloud height was linear with impeller frequency and with volume concentration. Suspensions with larger particles had a lower average cloud height, while the standard deviation for the temporal cloud height variation was larger. Two strong periodic phenomena were identified to be dominating the particle cloud height variations. The frequencies were linear with impeller speed, resulting in dimensionless frequencies of S-1 = 0.02-0.03 and S-2 = 0.05-0.06. The frequencies were affected by neither the particle size nor the volumetric concentration. The amplitude showed no dependency on the particle size, but the S-2 amplitude significantly decreases and S-1 increases with increasing solid concentration. The results were compared to LES/discrete element method simulations and showed a fair agreement.
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| 8. |
- Eng, Matthias, 1983
(författare)
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Flow structures in solid-liquid suspensions in mixing and confined jets
- 2014
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis is an investigation of the influence of solid particles on different liquid flow systems. Large-scale periodic fluctuations such as macro instabilities (MI) and particle cloud dynamics in a mixing vessel and confined jets were studied experimentally and compared to numerical results from CFD simulations. The influence of particle size (0.5mm-2mm), volumetric concentration (0%vol-20%vol) and impeller speed (20Hz-37.5Hz) on turbulent structures and large-scale periodic phenomena were examined. Two-component Laser Doppler Velocimetry (LDV) measurements were conducted at different locations in a confined jet and in a mixing vessel. Video processing was used to observe the dynamic behaviours of a particle cloud and to track the cloud height. Spectral analyses were conducted using the Lomb algorithm to collect information about dominant periodicities in a continuous flow and particle cloud behaviour.The flow conditions were numerically modelled with a Euler-Lagrange approach, treating the particles as a discrete phase and solving flow structures with an LES model. Numerical findings concerning MI phenomena, particle cloud spectra and local particle concentrations were compared to experimentally obtained data.The results showed that all identified dominant frequencies were linear with impeller speed, resulting in a constant Strouhal number. The frequency of continuous-phase MI phenomena and of particle cloud dynamics was not influenced by the addition of solids. However, the amplitudes of the dominant frequencies in fluid MI phenomena, as well as in variations of particle cloud height, were reduced by increasing the concentration of solids. Spectra obtained with numerical simulations showed the same dominant frequency peaks as identified in the experiments. It was possible to track the local particle concentration inside a particle cloud and to detect the instantaneous cloud surface.The Root Mean Square (RMS) values in the confined jet increased at high particle loadings; the increase was particularly pronounced in the shear layer close to the nozzle. With increasing particle size, a greater effect on the RMS values could be observed. Large-scale instabilities in the jet could be identified in the spectra of the flow. The particles had a slightly stabilizing effect on the jet, and moved the instability downstream, while the frequency was unaffected.
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| 9. |
- Eng, Matthias, 1983
(författare)
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Flow structures in solid-liquid suspensions in mixing and confined jets
- 2012
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis investigates the influence of solid particles on different liquid flow systems.Large-scale periodic fluctuations such as macro instability (MI) phenomena in a mixingvessel and jet flows in a confined jet were experimentally analyzed by means of LDV. Theinfluences of different sized (0.5mm-2mm) glass particles (0%vol - 6.2%vol) on the velocityand turbulence distribution in a jet were investigated, as well as the effects of varying theamounts of solid particles (up to 11.8%vol) on the frequency and amplitude of macro instabilities.Two component LDV measurements were conducted at different locations in thejet and in the mixing vessel. The values were evaluated using the Lomb algorithm to obtainfrequency spectra of the liquid flow. The average axial and lateral velocities, as well asRMS distributions, were determined together with the integral length scale in the confinedjet to analyse particle effect. The particle Stoke number was evaluated for the different sizedparticles and the different flow situations.The results showed that the MI frequency is not influenced by the addition of solids. However,the MI amplitude was reduced by the addition of the solid phase although still detectableup to the highest concentration measured (11.8 %vol). The particles (1.5mm) witha Stokes number of 1.1, related to the time scale of MI phenomena, caused an increase inMI strength at intermediate solids loading. This phenomenon could not be observed forsmaller particles.No change in the rate of decrease of the centreline velocity or the jet expansion ratio couldbe observed in the confined jet configuration. The RMS values in the jet increased at highparticle loadings; the increase was particularly pronounced in the shear layer close to thenozzle. With increasing particle size a greater effect on the RMS values could be observed.The frequency spectra of the flow and the strength of the large-scale instabilities were onlyaffected by the suspension with the 2mm particles. The 2mm particles had a stabilizingeffect on the jet and moved the instability further downstream while the frequency wasunaffected.
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| 10. |
- Eng, Matthias, 1983, et al.
(författare)
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Influence of solids on macro-instabilities in a stirred tank
- 2012
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Ingår i: Chemical Engineering Research and Design. - : Elsevier BV. - 0263-8762 .- 1744-3563. ; 90:8, s. 1052-1062
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Tidskriftsartikel (refereegranskat)abstract
- Measurements were conducted in a cylindrical tank stirred with a PBT in order to study the effect of varying amounts of suspended solids, up to 11.8% by volume, on the frequency and amplitude of macro-instabilities (MI). Solid glass particles of three different sizes were used in order to investigate the influence of the particle Stokes number. Measurements were made at 18 different locations in the vessel using laser Doppler anemometry (LDA) and were evaluated with the Lomb algorithm to obtain the frequency spectrum of the liquid flow. The results showed that the MI frequency is not influenced by the addition of solids. However, the MI amplitude was reduced by the addition of the solid phase although still detectable up to the highest concentration measured (11.8 vol.%). In the studied system there seems to be a difference dependent on the particle Stokes number.
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| 11. |
- Eng, Matthias, 1983, et al.
(författare)
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Large Eddy Simulation of the influence of solids on macro instability frequency in a stirred tank
- 2015
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Ingår i: Chemical Engineering Journal. - : Elsevier BV. - 1385-8947. ; 259, s. 900-910
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Tidskriftsartikel (refereegranskat)abstract
- The mixing flow in a cylindrical tank stirred with a PBT was simulated with a LES model with Eulerian–Lagrangian approach, in order to study the effect of varying amounts of suspended solids on the frequency and amplitude of macro instabilities (MI). The dispersed phase was reassembled solid glass particles of two different sizes (1 mm, 2 mm) and varying concentrations (up to 3% by volume). The continuous phase velocities were sampled at 18 different locations and were evaluated with the Lomb algorithm to obtain frequency spectra of the flow. The results showed that the MI could be detected in all suspensions and that the frequency is not influenced by the addition of solids. However, the MI became less prominent with increasing number of particles. A periodic fluctuation of the baffle jet could be observed with identical frequency. All results compare fairly well to previously obtained experimental data.
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| 12. |
- Eng, Matthias, 1983, et al.
(författare)
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Measurement of Continuous Phase Velocities in a Confined Solid-Liquid Jet Using LDV
- 2014
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Ingår i: Chemical Engineering Communications. - : Informa UK Limited. - 0098-6445 .- 1563-5201. ; 201:11, s. 1497-1513
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Tidskriftsartikel (refereegranskat)abstract
- A two-component LDV was used to investigate how flow structures in a liquid jet are influenced by the presence of solid particles. Solid glass spheres with a density of 2.5 kg/dm(3) and three different sizes (0.5 mm, 1 mm, and 2mm) at different solids loading (0-6.2 vol.%) were used as particles, while water served as continuous phase. No significant influence of the solid particles on the rate of decrease in the centerline liquid velocity or the jet expansion ratio could be observed. Two flow regimes were identified: a stable jet characterized by a symmetric shear layer close to the nozzle, and a flow dominated by large-scale instabilities farther from the nozzle. The spreading of particles was dominated by interparticle collisions in the region close to the nozzle and by jet instability in the region farther from the nozzle. With increased solids loading increased liquid RMS values in the region close to the nozzle could be found. The effect on RMS values was larger with larger particles. For the 1mm particles the RMS increased in this region, but decreased in the region farther from the nozzle. The presence of 2mm particles acted to stabilize the jet, and the instability moved farther downstream. Suspensions with smaller particles had no effect on the instability, strength, or location.
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| 13. |
- Krauss, Tobias, et al.
(författare)
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Preventive medicine of von Hippel-Lindau disease-associated pancreatic neuroendocrine tumors
- 2018
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Ingår i: Endocrine-Related Cancer. - : BIOSCIENTIFICA LTD. - 1351-0088 .- 1479-6821. ; 25:9, s. 783-793
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Tidskriftsartikel (refereegranskat)abstract
- Pancreatic neuroendocrine tumors (PanNETs) are rare in von Hippel-Lindau disease (VHL) but cause serious morbidity and mortality. Management guidelines for VHL-PanNETs continue to be based on limited evidence, and survival data to guide surgical management are lacking. We established the European-American-Asian-VHL-PanNET-Registry to assess data for risks for metastases, survival and long-term outcomes to provide best management recommendations. Of 2330 VHL patients, 273 had a total of 484 PanNETs. Median age at diagnosis of PanNET was 35 years (range 10-75). Fifty-five (20%) patients had metastatic PanNETs. Metastatic PanNETs were significantly larger (median size 5 vs 2 cm; P < 0.001) and tumor volume doubling time (TVDT) was faster (22 vs 126 months; P = 0.001). All metastatic tumors were >= 2.8 cm. Codons 161 and 167 were hotspots for VHL germline mutations with enhanced risk for metastatic PanNETs. Multivariate prediction modeling disclosed maximum tumor diameter and TVDT as significant predictors for metastatic disease (positive and negative predictive values of 51% and 100% for diameter cut-off >= 2.8 cm, 44% and 91% for TVDT cut-off of <= 24 months). In 117 of 273 patients, PanNETs > 1.5 cm in diameter were operated. Ten-year survival was significantly longer in operated vs non-operated patients, in particular for PanNETs < 2.8 cm vs >= 2.8 cm (94% vs 85% by 10 years; P = 0.020; 80% vs 50% at 10 years; P = 0.030). This study demonstrates that patients with PanNET approaching the cut-off diameter of 2.8 cm should be operated. Mutations in exon 3, especially of codons 161/167 are at enhanced risk for metastatic PanNETs. Survival is significantly longer in operated non-metastatic VHL-PanNETs.
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| 14. |
- Kucukcoskun, Korcan, et al.
(författare)
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Prediction of exterior wind noise generated by a side-mirror of an SUV
- 2016
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Ingår i: Proceedings of the INTER-NOISE 2016 - 45th International Congress and Exposition on Noise Control Engineering: Towards a Quieter Future. ; , s. 7401-7411
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Konferensbidrag (refereegranskat)abstract
- Simulation methods predicting the aerodynamic and aeroacoustic performances of car components at an early stage of their design cycle are of the high importance. This paper focuses on the validation of an acoustic simulation technique for side-mirror noise for observers located outside of the car compartment, typical to component testing in anechoic wind tunnels. A hybrid simulation approach is accounted, where flow and acoustic-fields are separated. The flow field is computed a priori with an incompressible flow solver. The acoustic-field is then computed based on the information extracted from the CFD solver. A surface dipole based acoustic simulation technique is employed where the unsteady aerodynamic pressure loading on the side-mirror surface is treated as acoustic source field. The effect of the volumetric sources is then accounted in the surface source definition without exporting them from the CFD solver. The paper provides the acoustic simulations for two configurations on side mirror. The results are compared to data obtained in wind-tunnel measurement on the SUV.
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| 15. |
- Soltani, Amin, et al.
(författare)
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Direct nanoscopic observation of plasma waves in the channel of a graphene field-effect transistor
- 2020
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Ingår i: Light: Science and Applications. - : Springer Science and Business Media LLC. - 2047-7538 .- 2095-5545. ; 9:1
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Plasma waves play an important role in many solid-state phenomena and devices. They also become significant in electronic device structures as the operation frequencies of these devices increase. A prominent example is field-effect transistors (FETs), that witness increased attention for application as rectifying detectors and mixers of electromagnetic waves at gigahertz and terahertz frequencies, where they exhibit very good sensitivity even high above the cut-off frequency defined by the carrier transit time. Transport theory predicts that the coupling of radiation at THz frequencies into the channel of an antenna-coupled FET leads to the development of a gated plasma wave, collectively involving the charge carriers of both the two-dimensional electron gas and the gate electrode. In this paper, we present the first direct visualization of these waves. Employing graphene FETs containing a buried gate electrode, we utilize near-field THz nanoscopy at room temperature to directly probe the envelope function of the electric field amplitude on the exposed graphene sheet and the neighboring antenna regions. Mapping of the field distribution documents that wave injection is unidirectional from the source side since the oscillating electrical potentials on the gate and drain are equalized by capacitive shunting. The plasma waves, excited at 2 THz, are overdamped, and their decay time lies in the range of 25–70 fs. Despite this short decay time, the decay length is rather long, i.e., 0.3-0.5 μm, because of the rather large propagation speed of the plasma waves, which is found to lie in the range of 3.5–7 × 10^6 m/s, in good agreement with theory. The propagation speed depends only weakly on the gate voltage swing and is consistent with the theoretically predicted 1414 power law.
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| 16. |
- Soltani, Amin, et al.
(författare)
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Unveiling the plasma wave in the channel of graphene field-effect transistor
- 2019
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Ingår i: International Conference on Infrared, Millimeter, and Terahertz Waves, IRMMW-THz. - 2162-2027 .- 2162-2035. ; 2019-September
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Konferensbidrag (refereegranskat)abstract
- Coupling an electromagnetic wave at GHz to THz frequencies into the channel of a graphene field-effect transistor (GFET) provokes collective charge carrier oscillations of the two-dimensional electron gas (2DEG) known as plasma waves. Here, we report the very first experimental and direct mapping of the electric field distribution in a gated GFET at nanometer length scales using scattering-type scanning near-field microscopy (s-SNOM) at 2 THz. Based on the experimental results we deduce the plasma wave velocity for different gate bias voltages, which is in good agreement with the theoretical prediction.
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