| 1. |
- Rajewsky, N., et al.
(author)
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LifeTime and improving European healthcare through cell-based interceptive medicine
- 2020
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In: Nature. - : Springer Nature. - 0028-0836 .- 1476-4687. ; 587:7834, s. 377-386
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Journal article (peer-reviewed)abstract
- LifeTime aims to track, understand and target human cells during the onset and progression of complex diseases and their response to therapy at single-cell resolution. This mission will be implemented through the development and integration of single-cell multi-omics and imaging, artificial intelligence and patient-derived experimental disease models during progression from health to disease. Analysis of such large molecular and clinical datasets will discover molecular mechanisms, create predictive computational models of disease progression, and reveal new drug targets and therapies. Timely detection and interception of disease embedded in an ethical and patient-centered vision will be achieved through interactions across academia, hospitals, patient-associations, health data management systems and industry. Applying this strategy to key medical challenges in cancer, neurological, infectious, chronic inflammatory and cardiovascular diseases at the single-cell level will usher in cell-based interceptive medicine in Europe over the next decade.
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| 2. |
- Reimerdes, H., et al.
(author)
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Overview of the TCV tokamak experimental programme
- 2022
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In: Nuclear Fusion. - : IOP Publishing. - 1741-4326 .- 0029-5515. ; 62:4
-
Journal article (peer-reviewed)abstract
- The tokamak a configuration variable (TCV) continues to leverage its unique shaping capabilities, flexible heating systems and modern control system to address critical issues in preparation for ITER and a fusion power plant. For the 2019-20 campaign its configurational flexibility has been enhanced with the installation of removable divertor gas baffles, its diagnostic capabilities with an extensive set of upgrades and its heating systems with new dual frequency gyrotrons. The gas baffles reduce coupling between the divertor and the main chamber and allow for detailed investigations on the role of fuelling in general and, together with upgraded boundary diagnostics, test divertor and edge models in particular. The increased heating capabilities broaden the operational regime to include T (e)/T (i) similar to 1 and have stimulated refocussing studies from L-mode to H-mode across a range of research topics. ITER baseline parameters were reached in type-I ELMy H-modes and alternative regimes with 'small' (or no) ELMs explored. Most prominently, negative triangularity was investigated in detail and confirmed as an attractive scenario with H-mode level core confinement but an L-mode edge. Emphasis was also placed on control, where an increased number of observers, actuators and control solutions became available and are now integrated into a generic control framework as will be needed in future devices. The quantity and quality of results of the 2019-20 TCV campaign are a testament to its successful integration within the European research effort alongside a vibrant domestic programme and international collaborations.
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| 3. |
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| 4. |
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| 5. |
- Theuns, J., et al.
(author)
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Global investigation and meta-analysis of the C9orf72 (G4C2)n repeat in Parkinson disease
- 2014
-
In: Neurology. - : Ovid Technologies (Wolters Kluwer Health). - 1526-632X .- 0028-3878. ; 83:21, s. 13-1906
-
Journal article (peer-reviewed)abstract
- OBJECTIVES: The objective of this study is to clarify the role of (G4C2)n expansions in the etiology of Parkinson disease (PD) in the worldwide multicenter Genetic Epidemiology of Parkinson's Disease (GEO-PD) cohort. METHODS: C9orf72 (G4C2)n repeats were assessed in a GEO-PD cohort of 7,494 patients diagnosed with PD and 5,886 neurologically healthy control individuals ascertained in Europe, Asia, North America, and Australia. RESULTS: A pathogenic (G4C2)n>60 expansion was detected in only 4 patients with PD (4/7,232; 0.055%), all with a positive family history of neurodegenerative dementia, amyotrophic lateral sclerosis, or atypical parkinsonism, while no carriers were detected with typical sporadic or familial PD. Meta-analysis revealed a small increase in risk of PD with an increasing number of (G4C2)n repeats; however, we could not detect a robust association between the C9orf72 (G4C2)n repeat and PD, and the population attributable risk was low. CONCLUSIONS: Together, these findings indicate that expansions in C9orf72 do not have a major role in the pathogenesis of PD. Testing for C9orf72 repeat expansions should only be considered in patients with PD who have overt symptoms of frontotemporal lobar degeneration/amyotrophic lateral sclerosis or apparent family history of neurodegenerative dementia or motor neuron disease.
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| 6. |
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| 7. |
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| 8. |
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| 9. |
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| 10. |
- Elsakka, Amr, et al.
(author)
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A mm-Wave Phased-Array Fed Torus Reflector Antenna with ±30° Scan Range for Massive-MIMO Base-Station Applications
- 2022
-
In: IEEE Transactions on Antennas and Propagation. - 0018-926X .- 1558-2221. ; 70:5, s. 3398-3410
-
Journal article (peer-reviewed)abstract
- A phased-array fed reflector antenna system is presented which can be used for mm-wave base station applications. The proposed system is designed to support massive-Multi-Input-Multi-Output (MIMO) scenarios within a wide coverage (±30°) in the azimuth plane and a limited coverage at the elevation plane. A design and characterization methodology has been established to optimize the system for the operation in various line-of-sight conditions by adopting the maximum-ratio-transmission (MRT) and zero-forcing (ZF) MIMO algorithms. A two-user MIMO case study has been considered for the evaluation of the key system performance metrics, i.e. the effective isotropic radiated power, power consumption, signal-to-noise-ratio (SNR), and signal-to-interference-plus-noise-ratio (SINR). This study demonstrates that the phased-array fed reflector concept has a major advantage over traditional direct-radiating phased array (DRPA) antennas to reduce energy consumption. In the present example, it requires 12–14 dB less transmitted power as compared to the MRT-beamformed DRPAs for the same SNR, and 26–27 dB less transmitted power relatively to ZF-beamformed DRPA systems for the same SINR. A prototype, employing a 55 cm diameter torus reflector and operating at 28 GHz-band, has been manufactured and tested. The measurement results agree well with simulations.
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| 11. |
- Meyer, E., et al.
(author)
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The state of the art in beyond 5G distributed massive multiple-input multiple-output communication system solutions
- 2022
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In: Open Research Europe. - : F1000 Research Ltd. - 2732-5121. ; 2
-
Research review (peer-reviewed)abstract
- Beyond fifth generation (5G) communication systems aim towards data rates in the tera bits per second range, with improved and flexible coverage options, introducing many new technological challenges in the fields of network architecture, signal pro- cessing, and radio frequency front-ends. One option is to move towards cell-free, or distributed massive Multiple-Input Multiple-Output (MIMO) network architectures and highly integrated front-end solutions. This paper presents an outlook on be- yond 5G distributed massive MIMO communication systems, the signal processing, characterisation and simulation challenges, and an overview of the state of the art in millimetre wave antennas and electronics.
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| 12. |
- Acke, B., et al.
(author)
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Herschel images of Fomalhaut An extrasolar Kuiper belt at the height of its dynamical activity
- 2012
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In: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 540, s. Article Number: A125 -
-
Journal article (peer-reviewed)abstract
- Context. Fomalhaut is a young (2 +/- 1 x 10(8) years), nearby (7.7 pc), 2 M-circle dot star that is suspected to harbor an infant planetary system, interspersed with one or more belts of dusty debris. Aims. We present far-infrared images obtained with the Herschel Space Observatory with an angular resolution between 5.7 '' and 36.7 '' at wavelengths between 70 mu m and 500 mu m. The images show the main debris belt in great detail. Even at high spatial resolution, the belt appears smooth. The region in between the belt and the central star is not devoid of material; thermal emission is observed here as well. Also at the location of the star, excess emission is detected. We aim to construct a consistent image of the Fomalhaut system. Methods. We use a dynamical model together with radiative-transfer tools to derive the parameters of the debris disk. We include detailed models of the interaction of the dust grains with radiation, for both the radiation pressure and the temperature determination. Comparing these models to the spatially resolved temperature information contained in the images allows us to place strong constraints on the presence of grains that will be blown out of the system by radiation pressure. We use this to derive the dynamical parameters of the system. Results. The appearance of the belt points toward a remarkably active system in which dust grains are produced at a very high rate by a collisional cascade in a narrow region filled with dynamically excited planetesimals. Dust particles with sizes below the blow-out size are abundantly present. The equivalent of 2000 one-km-sized comets are destroyed every day, out of a cometary reservoir amounting to 110 Earth masses. From comparison of their scattering and thermal properties, we find evidence that the dust grains are fluffy aggregates, which indicates a cometary origin. The excess emission at the location of the star may be produced by hot dust with a range of temperatures, but may also be due to gaseous free-free emission from a stellar wind.
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| 13. |
- Anjos, Eduardo V.P., et al.
(author)
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FORMAT: A Reconfigurable Tile-Based Antenna Array System for 5G and 6G Millimeter-Wave Testbeds
- 2022
-
In: IEEE Systems Journal. - 1932-8184 .- 1937-9234. ; 16:3, s. 4489-4500
-
Journal article (peer-reviewed)abstract
- This article introduces the FORMAT array, a reconfigurable millimeter-wave antenna array platform based on antenna tiles. FORMAT stands for Flexible Organization and Reconfiguration of Millimeter-wave Antenna Tiles, which is a unique hardware solution aiming to implement and demonstrate a variety of antenna array concepts, as well as different array architectures and configurations from the same basic module, providing even benchmark between different solutions and thus valuable insights into fifth-generation (5G) and beyond-5G antenna systems. The combination of a minimum-sized tile with 3D-printed frame parts enables antenna arrays of a variety of sizes, allows multiple beamforming architectures, and a range of different antenna element positioning in the array. The hardware implementation is thoroughly described, with a few different array assemblies being manufactured and measured, validating their antenna performance with over-the-air measurements. Finally, using FORMAT hardware as both base station and user equipment, a 5-m wireless communication link was set up, achieving 4.8 Gbps downlink speed with QAM64 modulation.
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| 14. |
- Bressner, Thomas A.H., et al.
(author)
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Cell Partitioning Antenna System Performance in Multi-User Scenarios for mmWave Communications
- 2021
-
In: IEEE Access. - 2169-3536 .- 2169-3536. ; 9, s. 127141-127149
-
Journal article (peer-reviewed)abstract
- Fixed-beam, high-gain antenna systems can be used for a finer partitioning of the currently used cell-sectoring. This partitioning has the benefit of reducing the number of users seen per antenna beam, which reduces interference. Furthermore, the high antenna gain allows for a high effective isotropic radiated power while keeping the transmit power low. In this paper, we study the performance of such a fixed-beam, high gain antenna system design for millimeter-wave mobile communications. The antenna system is designed to keep the inter-sector interference in a multi-site scenario low. The performance is analyzed for single- and multi-user environments. In single-input single-output mode, the 50th percentile of the signal-to-interference-plus-noise ratio lies between 12.5 dB to 39.7 dB if 3 to 0 interferers are present, respectively. For multiple-input multiple-output transmission using zero-forcing, the signal-to-interference-plus-noise ratio increases and the 50th percentile ranges from 36.1 dB to 43.3 dB if 3 to 0 interferes are present, respectively. By using maximum ratio transmission, the best performance is achieved with no interferers present, while a plunge in performance is observed with interferers. Furthermore, the study revealed that the narrow beam antenna system can also provide a clear signal separation for small spatial separations. In the given example, the signal-to-interference-plus-noise ratio is larger than 32.1 dB with 11 active antenna elements, where 2.8 meters separate the users. Hence, the paper shows that the cell-partitioning antenna systems provide coverage in the desired area while keeping the inter-sector interference low, and the considered transmission techniques can be used for situation optimized mobile communication links.
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| 15. |
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| 16. |
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| 17. |
- Smolders, A., et al.
(author)
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Robust optimization strategies for contour uncertainties in online adaptive radiation therapy
- 2024
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In: Physics in Medicine and Biology. - : IOP Publishing. - 0031-9155 .- 1361-6560. ; 69:16
-
Journal article (peer-reviewed)abstract
- Objective. Online adaptive radiation therapy requires fast and automated contouring of daily scans for treatment plan re-optimization. However, automated contouring is imperfect and introduces contour uncertainties. This work aims at developing and comparing robust optimization strategies accounting for such uncertainties. Approach. A deep-learning method was used to predict the uncertainty of deformable image registration, and to generate a finite set of daily contour samples. Ten optimization strategies were compared: two baseline methods, five methods that convert contour samples into voxel-wise probabilities, and three methods accounting explicitly for contour samples as scenarios in robust optimization. Target coverage and organ-at-risk (OAR) sparing were evaluated robustly for simplified proton therapy plans for five head-and-neck cancer patients. Results. We found that explicitly including target contour uncertainty in robust optimization provides robust target coverage with better OAR sparing than the baseline methods, without increasing the optimization time. Although OAR doses first increased when increasing target robustness, this effect could be prevented by additionally including robustness to OAR contour uncertainty. Compared to the probability-based methods, the scenario-based methods spared the OARs more, but increased integral dose and required more computation time. Significance. This work proposed efficient and beneficial strategies to mitigate contour uncertainty in treatment plan optimization. This facilitates the adoption of automatic contouring in online adaptive radiation therapy and, more generally, enables mitigation also of other sources of contour uncertainty in treatment planning.
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| 18. |
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| 19. |
- Bude, R. X.F., et al.
(author)
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A System-Performance-Based Comparison of Sparse Regular and Irregular Antenna Arrays for Millimeter-Wave Multi-User MIMO Base Stations
- 2022
-
In: Electronics (Switzerland). - : MDPI AG. - 2079-9292. ; 11:3
-
Journal article (peer-reviewed)abstract
- A system-level study was conducted that evaluated the system performance of various dense and sparse antenna array configurations for application in millimeter-wave multi-user multiple-input multiple-output base stations. The performance was evaluated by investigating the probability that a user experiences an outage when a zero-forcing pre-coder is used in a random line of sight scenario. This paper shows that the outage probability significantly decreased when irregular sparse arrays were used rather than regular sparse or regular dense arrays. A re-configurable linear array was designed and realized as a demonstrator. It used 3D-printed aluminum box horn antenna elements that had wide scanning range in the azimuthal plane and a small scanning range in the elevation plane. For the demonstrator, it was shown that the outage probability was reduced from 3.85% to 0.64% by moving from a sparse regularly spaced array to a sparse randomly spaced array. This amounted to an improvement of a factor of six. The sparse topology allowed for the usage of large antenna elements that had an increased gain and still achieved wide-angle scanning, while reducing mutual coupling to a minimum.
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| 20. |
- Bude, R. X.F., et al.
(author)
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Sparse Array Topologies for 5G mmWave Base-Stations: A System-Level Study
- 2020
-
In: 2020 IEEE International Symposium on Antennas and Propagation and North American Radio Science Meeting, IEEECONF 2020 - Proceedings. ; , s. 1295-1296
-
Conference paper (peer-reviewed)abstract
- A system-level study is conducted that evaluates the performance of various sparse array topologies for application in 5G base-stations. The performance metric is the probability a user experiences an outage, when applying a Zero-Forcing precoder in a Line-of-Sight scenario. The outage probability is shown to significantly decrease for sparse irregular arrays as compared to sparse regular and dense regular arrays. A re-configurable sparse array design at 28.5GHz is realized as a demonstrator.
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| 21. |
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| 22. |
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| 23. |
- Eckhard, A, et al.
(author)
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Water permeability of the mammalian cochlea : functional features of an aquaporin-facilitated water shunt at the perilymph-endolymph barrier
- 2014
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In: Pflügers Archiv. - : Springer Science and Business Media LLC. - 0031-6768 .- 1432-2013. ; 466:10, s. 1963-1985
-
Journal article (peer-reviewed)abstract
- The cochlear duct epithelium (CDE) constitutes a tight barrier that effectively separates the inner ear fluids, endolymph and perilymph, thereby maintaining distinct ionic and osmotic gradients that are essential for auditory function. However, in vivo experiments have demonstrated that the CDE allows for rapid water exchange between fluid compartments. The molecular mechanism governing water permeation across the CDE remains elusive. We computationally determined the diffusional (P D) and osmotic (P f) water permeability coefficients for the mammalian CDE based on in silico simulations of cochlear water dynamics integrating previously derived in vivo experimental data on fluid flow with expression sites of molecular water channels (aquaporins, AQPs). The P D of the entire CDE (P D = 8.18 × 10(-5) cm s(-1)) and its individual partitions including Reissner's membrane (P D = 12.06 × 10(-5) cm s(-1)) and the organ of Corti (P D = 10.2 × 10(-5) cm s(-1)) were similar to other epithelia with AQP-facilitated water permeation. The P f of the CDE (P f = 6.15 × 10(-4) cm s(-1)) was also in the range of other epithelia while an exceptionally high P f was determined for an epithelial subdomain of outer sulcus cells in the cochlear apex co-expressing AQP4 and AQP5 (OSCs; P f = 156.90 × 10(-3) cm s(-1)). The P f/P D ratios of the CDE (P f/P D = 7.52) and OSCs (P f/P D = 242.02) indicate an aqueous pore-facilitated water exchange and reveal a high-transfer region or "water shunt" in the cochlear apex. This "water shunt" explains experimentally determined phenomena of endolymphatic longitudinal flow towards the cochlear apex. The water permeability coefficients of the CDE emphasise the physiological and pathophysiological relevance of water dynamics in the cochlea in particular for endolymphatic hydrops and Ménière's disease.
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| 24. |
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| 25. |
- Konstantinou, Dimitrios, et al.
(author)
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5G RAN architecture based on analog radio-over-fiber fronthaul over UDWDM-PON and phased array fed reflector antennas
- 2020
-
In: Optics Communications. - : Elsevier BV. - 0030-4018. ; 454
-
Journal article (peer-reviewed)abstract
- This manuscript introduces a 5G radio access network architecture concept based on ultra-dense wavelength division multiplexing (UDWDM) and incorporating an optical fronthaul network that uses a novel wireless antenna system for radio frequency transmission and reception. A ring topology is proposed where optical signals travel within the 5G UDWDM passive optical networks and millimeter waves are generated in the optical line terminals by optical heterodyning. The wireless transmission of the millimeter waves is conducted by an innovative phased array fed reflector antenna approach for mobile communications that grants high antenna gain due to highly focused radiation characteristics, as well as multiplexing gain by multiple beam generation. Furthermore, beam steering is provided by a radio frequency analog beamformer network. Finally, implementation options synthesizing the total system are discussed.
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| 26. |
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| 27. |
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| 28. |
- Morgan, N, et al.
(author)
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Convolutional neural network for automatic maxillary sinus segmentation on cone-beam computed tomographic images
- 2022
-
In: Scientific reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 12:1, s. 7523-
-
Journal article (peer-reviewed)abstract
- An accurate three-dimensional (3D) segmentation of the maxillary sinus is crucial for multiple diagnostic and treatment applications. Yet, it is challenging and time-consuming when manually performed on a cone-beam computed tomography (CBCT) dataset. Recently, convolutional neural networks (CNNs) have proven to provide excellent performance in the field of 3D image analysis. Hence, this study developed and validated a novel automated CNN-based methodology for the segmentation of maxillary sinus using CBCT images. A dataset of 264 sinuses were acquired from 2 CBCT devices and randomly divided into 3 subsets: training, validation, and testing. A 3D U-Net architecture CNN model was developed and compared to semi-automatic segmentation in terms of time, accuracy, and consistency. The average time was significantly reduced (p-value < 2.2e−16) by automatic segmentation (0.4 min) compared to semi-automatic segmentation (60.8 min). The model accurately identified the segmented region with a dice similarity co-efficient (DSC) of 98.4%. The inter-observer reliability for minor refinement of automatic segmentation showed an excellent DSC of 99.6%. The proposed CNN model provided a time-efficient, precise, and consistent automatic segmentation which could allow an accurate generation of 3D models for diagnosis and virtual treatment planning.
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| 29. |
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| 30. |
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| 31. |
- Smolders, Thijs J. A. M., et al.
(author)
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Diffusivity Tensors of Br and Cs Vacancies in Biaxially Strained Perovskite CsPbBr3
- 2024
-
In: Chemistry of Materials. - : American Chemical Society (ACS). - 0897-4756 .- 1520-5002. ; 36:5, s. 2334-2345
-
Journal article (peer-reviewed)abstract
- Using density functional theory and kinetic modeling, we investigate the relationship between imposed biaxial strain and Br- and Cs-vacancy diffusion in orthorhombic (Pnma) CsPbBr3, in the dilute limit. We calculate the activation energies for the hopping of vacancies between all pairs of nearest-neighbor lattice sites and use the resulting values to parametrize a kinetic scheme and thereby to calculate vacancy diffusivity tensors. Our results indicate that the relationship between strain and vacancy diffusion is significantly more complex than previously thought – activation energies for vacancy hopping may increase or decrease for both negative (compressive) or positive (tensile) imposed biaxial strain, depending both on the plane in which strain is imposed and the particular pair of sites between which the vacancy hops, and the relationships are nonlinear in general and often nonmonotonic. Furthermore, we find that the influence of imposed biaxial strain on the diffusivity is significantly greater for Cs vacancies than for Br vacancies, and in particular, that values of Cs-vacancy diffusivity approach those of Br-vacancy diffusivity under certain conditions.
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| 32. |
- Aljarosha, Alhassan, 1982, et al.
(author)
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Performance Analysis of an Integrated Multi-Channel Power Amplifier Incorporating an IC-to-Waveguide Transition
- 2021
-
In: 2021 15TH EUROPEAN CONFERENCE ON ANTENNAS AND PROPAGATION (EUCAP). - 2164-3342.
-
Conference paper (peer-reviewed)abstract
- This paper studies the power combiner efficiency of multiple Power Amplifier (PA) output signals that are combined within a low-loss contactless transition, intrinsically having low isolation characteristics. Since the PA performance is sensitive to load impedance variations, poor isolation may affect each PA performance, thereby reducing the overall power combiner efficiency. Load impedance variations can e.g. be due to process, supply-voltage and temperature variations. A four-way spatial power combiner (SPC) design is compared to an on-chip Wilkinson Power Combiner (WPC) implemented in 0.13 mu m SiGe BiCMOS technology incorporating a 50 Omega impedance matching network. The WPC occupies 84% more area than the non-isolating SPC. Moreover, the non-isolating SPC has an average efficiency 14% larger than the WPC. For physically realistic variations, simulated results show a sigma-variation of 2.81 mW in P-out and 0.87 % in PAE for the non-isolating SPC, and 2.34 mW in P-out and 0.45 % in PAE for the WPC (@1 dB compression).
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| 33. |
- Aljarosha, Alhassan, 1982, et al.
(author)
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Performance comparison of silicon substrates for IC-waveguide integration based on a contactless transition at mm-wave frequencies
- 2019
-
In: 2019 IEEE International Symposium on Antennas and Propagation and USNC-URSI Radio Science Meeting, APSURSI 2019 - Proceedings. ; July 2019, s. 1081-1082
-
Conference paper (peer-reviewed)abstract
- This paper presents a comparison between different silicon (Si) substrates used in Si-based IC technologies at E-Band (71-86 GHz). A unique low-loss and compact contactless transition from a silicon IC (p-doped substrate) to a metal waveguide is used. The proposed transition incorporates a spatial power combiner to enable direct electromagnetic coupling from an array of patches on the IC to a metal waveguide. This design enables a high-power transition from an IC to a waveguide and/or antenna at millimeter-wave (mm-wave) frequencies, where a galvanic contact between the two parts is avoided.
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| 34. |
- Aljarosha, Alhassan, 1982, et al.
(author)
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Silicon-Based IC-Waveguide Integration for Compact and High-Efficiency mm-Wave Spatial Power Combiners
- 2021
-
In: IEEE Transactions on Components, Packaging and Manufacturing Technology. - 2156-3985 .- 2156-3950. ; 11:7, s. 1115-1121
-
Journal article (peer-reviewed)abstract
- A novel and compact millimeter-wave spatial power combiner is developed integrating a Silicon-based integrated circuit (IC) in a metal waveguide. As an initial step towards integrating a silicon-based active IC in a waveguide, a passive back-to-back transition incorporating a 4-way spatial power splitter and combiner is realized at E-band (71–86 GHz). In contrast to existing solutions, the proposed design considers power splitting and combining using a low-loss wireless transition between the IC and the waveguide. The proposed back-to-back structure comprises an IC implemented using Institute for High Performance Microelectronics (IHP’s) 0.13μm SiGe BiCMOS technology integrated into the H-plane of a waveguide. The IC is post-processed and assembled in the waveguide prototype. The measured prototype shows a return loss better than 13 dB, an average insertion loss of 1.7 dB for a single transition, and a fractional bandwidth of 26.4 % (69–90 GHz).
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| 35. |
- Aljarosha, Alhassan, 1982, et al.
(author)
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Toward Wide-Band Low-Loss Gap-Waveguide-Integrated Grid Amplifiers
- 2017
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In: 2017 International Symposium on Antennas and Propagation (ISAP). - 9781538604656 ; 2017-January
-
Conference paper (peer-reviewed)abstract
- A passive W-band 19-channel spatial power splitter/combiner is presented, for the applications in grid amplifiers design. The design employs a linear array of chip-to-air-filled waveguide contactless connections, and are directly integrated within a single-layer. The meta-material-based gap waveguide is used; it enables a low-loss low-profile solution. The quasi optical beamformer gives rise to a parallel-plate planar waveguide field which excites an array of contactless chip-to-waveguide transitions via step-tapered ridge gap waveguides. The other beamformer restores the field distribution (after amplification) and excites a wave going towards the waveguide output. Furthermore, the gap waveguide technology isolates the amplifiers from one another and provides a packaging solution in a single unit. The simulated return loss of the back-to-back structure is larger than 12 dB, while the insertion loss is smaller than 1.2 dB over the entire W-band (75-110 GHz).
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| 36. |
- Amani, Navid, 1985, et al.
(author)
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Multi-Panel Sparse Base Station Design with Physical Antenna Effects in Massive MU-MIMO
- 2020
-
In: IEEE Transactions on Vehicular Technology. - 0018-9545 .- 1939-9359. ; 69:6, s. 6500-6510
-
Journal article (peer-reviewed)abstract
- A novel base station antenna (BSA) configuration is presented to mitigate degrading physical antenna effects in massive multiple-input multiple-output (MIMO) systems, while minimizing implementation complexities. Instead of using a commonly considered single antenna panel comprising of many elements covering a wide field-of-view (FOV) of 120 degrees, L tilted panels are used employing L times fewer elements and L times smaller FOV per panel. The spatial resolution of each panel is enhanced by employing sparse arrays with suppressed (grating-lobe) radiation outside its corresponding FOV. Therefore, more directive antenna elements can be deployed in each panel to compensate for the effective isotropic radiated power (EIRP) reduction. While sectorisation reduces the antenna gain variation in 120 degrees FOV, cooperation among multiple panels in downlink beamforming is seen to be capable of inter-panel interference suppression for sum-rate enhancement. A network model is used as a multi-user (MU) MIMO simulator incorporating both antenna and channel effects. It is shown that when the number of base station antennas is ten times the number of users, the average downlink sum-rate in pure line-of-sight (LOS), rich and poor multipath environments is increased up to 60.2%, 23% and 11.1%, respectively, by multi-panel sparse arrays applying zero-forcing (ZF) precoding.
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| 37. |
- Amani, Navid, 1985, et al.
(author)
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Towards a Generic Model for MU-MIMO Analysis Including Mutual Coupling and Multipath Effects
- 2019
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In: 13th European Conference on Antennas and Propagation, EuCAP 2019. ; 2019
-
Conference paper (peer-reviewed)abstract
- A network model which accounts for antenna mutual coupling and multipath effects in a wireless channel is proposed as a tool to qualitatively evaluate the performance of a multi-user multiple-input multiple-output (MU-MIMO) system. The system performance is assessed when a zero-forcing (ZF) beamformed conventional uniform linear array (ULA) and a sparse array are employed as one sector of a base station antenna (BSA) in a single-cell network. It is shown that highly correlated user equipments (UEs) in a line-of-sight (LOS) scenario can be decorrelated to some extents, by a scattering environment in a non-line-of-sight (NLOS) scenario. This occurs due to increase of the spatial variation by a multipath effect. Furthermore, in both environments a sparse array realized by an increased interelement spacing is also capable for correlation reduction among users due to the narrower beams.
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| 38. |
- Elsakka, Amr, 1984, et al.
(author)
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A Design Concept of Power Efficient, High Gain Antenna System for mm-Waves Base Stations
- 2021
-
In: 2021 15TH EUROPEAN CONFERENCE ON ANTENNAS AND PROPAGATION (EUCAP). - 2164-3342.
-
Conference paper (peer-reviewed)abstract
- A design concept for a phased-array-fed reflector antenna system intended for millimeter-wave base stations is presented. This concept is motivated by the need for efficient beamforming antenna systems with reduced power consumption as compared to the presently considered fully-populated large-scale MIMO arrays. The main idea is to use a high-gain reflector antenna to maximize the effective isotropic radiated power. That in turn, allows minimizing the number of active antenna elements of the phased-array feed, and hence limit the total supplied power. The proposed reflector antenna system is based on a torus reflector which is illuminated by an offset phased-array feed. We show how to determine the antenna design parameters to achieve the desired cell coverage.
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| 39. |
- Farid, N., et al.
(author)
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Exploring Uniformity of Reverberation Chambers: Insights from Antenna Reflection Coefficient
- 2024
-
In: 18th European Conference on Antennas and Propagation, EuCAP 2024.
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Conference paper (peer-reviewed)abstract
- Reverberation chambers are widely recognized as a time-efficient testing facility for various applications. The spatial uniformity based on the power transfer function is a critical characteristic of the chamber that affects the measurement uncertainty. To gain more insights into the chamber behavior we introduce a complementary metric: the K-gamma factor. This metric, inspired by the well-established K-factor, quantifies the unstirred contributions of the chamber for each antenna individually and is highly sensitive to the chamber configuration and antenna placement. Analyzing this metric can help identify any undesired effect, such as specular reflections, and, ultimately, improve measurement accuracy. To highlight the usefulness of this metric, two different loading configurations of a reverberation chamber at millimeter-wave frequencies are evaluated as examples.
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| 40. |
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| 41. |
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| 42. |
- Gommers, A, et al.
(author)
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Radiocaesium soil-to-wood transfer in commercial willow short rotation coppice on contaminated farm land
- 2005
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In: Journal of Environmental Radioactivity. - : Elsevier BV. - 1879-1700 .- 0265-931X. ; 78:3, s. 267-287
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Journal article (peer-reviewed)abstract
- The feasibility of willow short rotation coppice (SRC) for energy production as a revaluation tool for severely radiocaesium-contaminated land was studied. The effects of crop age, clone and soil type on the radiocaesium. levels in the wood were assessed following sampling in 14 existing willow SRC fields, planted on radiocaesium-contaminated land in Sweden following Chernobyl deposition. There was only one plot where willow stands of different maturity (R6S2 and R5S4: R, root age and S. shoot age) and clone (Rapp and L78183 both of age category R5S4) were sampled and no significant differences were found. The soils differed among others in clay fraction (3-34%). radiocaesium interception potential (515-6884 meq kg(-1)). soil solution K (0.09-0.95 mM), exchangeable K (0.58-5-77 meq kg(-1)) and cation exchange capacity (31-250 meq kg(-1)). The soil-to-wood transfer factor (TF) of radiocaesium differed significantly between soil types. The TF recorded was generally small (0.00086-0.016 kg kg(-1)), except for willows established on sandy soil (0.19-0.46 kg kg(-1)). Apart from the weak yet significant exponential correlation between the Cs-TF and the solid/liquid distribution coefficient (R-2 = 0.54) or the radiocaesium interception potential. RIP (R-2 = 0.66), no single significant correlations between soil characteristics and TF were, found. The wood-soil solution Cs-137 concentration factor (CF) was significantly related to the potassium concentration in the soil solution. A different relation was, however, found between the sandy Trodje soils (CF = 1078.8 X m(K)(-1.83), R-2 = 0.99) and the other soils (CF = 35.75 X m(K) (-0.61), R-2 =0.61). Differences in the ageing rate of radiocaesium in the soil (hypothesised fraction of bioavailable caesium subjected to fast ageing for Trodje soils only 1 % compared to other soils), exchangeable soil K (0.8-1.8 meq kg(-1) for Trodje soils and 1.5-5.8 meq kg(-1) for the other soils) and the ammonium concentration in the soil solution (0.09-0.31 mM NH4+ for the Trodje soils compared to 0.003-0.11 mM NH4+ for the other soils) are put forward as potential factors explaining the higher CF and TF observed for the Trodje soils. Though from the dataset available it was not possible to unequivocally predict the soil-to-wood- transfer, the generally low TFs observed point to the particular suitability for establishment of SRC on radiocaesium-contaminated land.
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| 43. |
- Kaul, Piyush, et al.
(author)
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An E-band silicon-ic-to-waveguide contactless transition incorporating a low-loss spatial power combiner
- 2018
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In: Asia-Pacific Microwave Conference Proceedings, APMC. - 9784902339451 ; 2018-November, s. 1528-1530
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Conference paper (peer-reviewed)abstract
- A novel contactless transition from a (Bi)CMOS Silicon IC (p-doped substrate) to a metal waveguide in E-Band is presented. This transition also incorporates a spatial power combiner in air to enable direct electromagnetic coupling from an array of on-chip microstrip transmission lines to a single waveguide mode, and vice versa. The transition is relatively low loss and is particularly suitable for high-power mm-wave applications. The simulated return loss of a four-channel passive back-to-back transition is better than 10 dB over the frequency band ranging from 60-90 GHz (E-Band). The average insertion loss of a single transition is 1.31 dB over the entire E-Band.
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| 44. |
- Kaul, Piyush, et al.
(author)
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Spatial Power Combining and Impedance Matching Silicon IC-to-Waveguide Contactless Transition
- 2021
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In: EuMIC 2020 - 2020 15th European Microwave Integrated Circuits Conference. ; , s. 217-220
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Conference paper (peer-reviewed)abstract
- In this paper a new multi-step joint-design approach is described for a multi-channel power amplifier integrated with an IC-to-Waveguide transition. The approach enables an optimal impedance match of a waveguide to an integrated-circuit via a contactless transition. Spatial power combining with a non-isolated contactless transition is achieved in the input and output networks of the power amplifier. Simulation results are presented which are in agreement with the joint-design requirements. This methodology enables IC-to-Waveguide integration and provides a suitable approach for mm-wave system integration.
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| 45. |
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| 46. |
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| 47. |
- Smolders, Simon, et al.
(author)
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A Titanium(IV)-Based Metal-Organic Framework Featuring Defect-Rich Ti-O Sheets as an Oxidative Desulfurization Catalyst
- 2019
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In: Angewandte Chemie International Edition. - : Wiley. - 1433-7851 .- 1521-3773. ; 58:27, s. 9160-9165
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Journal article (peer-reviewed)abstract
- While titanium-based metal-organic frameworks (MOFs) have been widely studied for their (photo) catalytic potential, only a few Ti-IV MOFs have been reported owing to the high reactivity of the employed titanium precursors. The synthesis of COK-47 is now presented, the first Ti carboxylate MOF based on sheets of (TiO6)-O-IV octahedra, which can be synthesized with a range of different linkers. COK-47 can be synthesized as an inherently defective nanoparticulate material, rendering it a highly efficient catalyst for the oxidation of thiophenes. Its structure was determined by continuous rotation electron diffraction and studied in depth by X-ray total scattering, EXAFS, and solid-state NMR. Furthermore, its photoactivity was investigated by electron paramagnetic resonance and demonstrated by catalytic photodegradation of rhodamine 6G.
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| 48. |
- Svensson Grape, Erik, et al.
(author)
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Bismuth gallate coordination networks inspired by an active pharmaceutical ingredient
- 2022
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In: Dalton Transactions. - : Royal Society of Chemistry (RSC). - 1477-9226 .- 1477-9234. ; 51:37, s. 14221-14227
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Journal article (peer-reviewed)abstract
- The effect of solvent has been investigated for the synthesis of bismuth gallate compounds, of which the water-based bismuth subgallate has been used as an active pharmaceutical ingredient (API) for over a century. Using methanol as a solvent, two new bismuth gallates were acquired: first a flexible 3-periodic metal–organic framework (MOF) forms, which transforms upon extended synthesis times into a layered 2-periodic coordination polymer of the same bismuth-to-gallate ratio. The structures were determined by three-dimensional electron diffraction. Synthesis in ethanol resulted in the formation of the MOF phase, but not the layered phase. The layered material of the methanol-based synthesis was used as a Lewis acid catalyst due to its higher stability, showing a comparatively quick and regiospecific conversion of styrene oxide to 2-methoxy-2-phenylethanol, indicating the presence of open metal sites in the material. The acquisition of bismuth gallate structures of varying periodicity highlights the prospect of acquiring novel MOFs and coordination polymers from the same components of APIs.
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| 49. |
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