116 research outputs found
Corrigendum to “Photopolymerization-Enforced Stratification in Liquid Crystal Materials” [Progress in Polymer Science. 114, 2021, 101365]
No full textThe authors regret to inform that…. The author information and affiliation need to be corrected as below. Wei Zhaoa,b,*, Laurens T. de Haana,b, Dirk J. Broera,c, Yang Zhangd, Pengrong Lva, Guofu Zhoua,b,e,* a SCNU-TUE Joint Lab of Device Integrated Responsive Materials (DIRM), National Center for International Research on Green Optoelectronics, South China Normal University, No 378, West Waihuan Road, Guangzhou Higher Education Mega Center, 510006, Guangzhou China b Guangdong Provincial Key Laboratory of Optical Information Materials and Technology & Institute of Electronic Paper Displays, South China Academy of Advanced Optoelectronics, South China Normal University, Guangzhou 510006, PR China c Stimuli‐responsive Functional Materials and Devices, Department of Chemical Engineering and Chemistry, Eindhoven University of Technology, Den Dolech 2, Eindhoven, 5600 MB, the Netherlands d Solar Energy Research Institute, Yunnan Normal University, Kunming 650500, China e Shenzhen Guohua Optoelectronics Tech. Co. Ltd., Shenzhen 518110, China Author would like to apologize for the inconvenience caused
Swept-3-D Ultrasound Imaging of the Mouse Brain Using a Continuously Moving 1-D-Array - Part II: Functional Imaging
Get PDFFunctional ultrasound (fUS) using a 1-D-array transducer normally is insufficient to capture volumetric functional activity due to being restricted to imaging a single brain slice at a time. Typically, for volumetric fUS, functional recordings are repeated many times as the transducer is moved to a new location after each recording, resulting in a nonunique average mapping of the brain response and long scan times. Our objective was to perform volumetric 3-D fUS in an efficient and cost-effective manner. This was achieved by mounting a 1-D-array transducer to a high-precision motorized linear stage and continuously translating over the mouse brain in a sweeping manner. We show how the speed at which the 1-D-array is translated over the brain affects the sampling of the hemodynamic response (HR) during visual stimulation as well as the quality of the resulting power Doppler image (PDI). Functional activation maps were compared between stationary recordings, where only one functional slice is obtained for every recording, and our swept-3-D method, where volumetric fUS was achieved in a single functional recording. The results show that the activation maps obtained with our method closely resemble those obtained during a stationary recording for that same location, while our method is not restricted to functional imaging of a single slice. Lastly, a mouse brain subvolume of 6 mm is scanned at a volume rate of 1.5 s per volume, with a functional PDI reconstructed every 200\mu \text{m} , highlighting swept-3-D's potential for volumetric fUS. Our method provides an affordable alternative to volumetric fUS using 2-D-matrix transducers, with a high SNR due to using a fully sampled 1-D-array transducer, and without the need to repeat functional measurements for every 2-D slice, as is most often the case when using a 1-D-array. This places our swept-3-D method as a potentially valuable addition to conventional 2-D fUS, especially when investigating whole-brain functional connectivity, or when shorter recording durations are desired.Signal Processing System
A North Sea offshore grid governance model: The allocation of ownership and operating responsibilities for a Meshed Offshore Grid
No full textEU climate goals force EU member states to increase the share of renewable electricity generation in their respective electricity markets. To reach these climate goals, offshore wind energy is regarded as one of the main technologies that can contribute to a full transition towards a fossil-free electricity system. Furthermore, 230 Gigawatts (GW) of offshore wind is projected to be necessary within the EU. Additionally, the EU has the objective to further integrate electricity markets within its member states. This further integration will therefore need a substantial increase in interconnection capacity between the current electricity markets. Both the increase in offshore wind energy and the increase in interconnection capacity will require offshore electricity transmission infrastructure. Currently, offshore wind generation is connected through individual (radial) offshore grid connections and interconnection capacity used for cross border trade is still developed through point-to-point interconnection. However, a meshed offshore grid (MOG) can combine the aforementioned functions of evacuating offshore wind and interconnect electricity markets. Additionally, a MOG is expected to provide additional economic benefits compared with the individual development of offshore wind farms (OWF) grid connections and the interconnection capacity between electricity markets. While a MOG can provide potential economic benefits, current development of a MOG is still lacking, caused by a variety of economic and regulatory knowledge gaps that need to be addressed. One of these knowledge gaps is which governance model, that allocates the responsibilities regarding the ownership and operation of such a MOG, is preferable for coordinated offshore grid developments. This research project is therefore focussing on this knowledge gap. In order to address this gap, an analytical framework is created through a literature review and desk research that provides both a foundation to conceptually develop the design space of a governance model, while also providing the tools to analyse the expected performance of a governance model. Additionally, a quantitative comparative analysis of currently applied governance models for individual OWF grid connections is performed to provide input for the analysis of governance models that can be applied for a MOG. Through the design space, four different governance models were constructed and analysed, based on the analytical framework. Three of the constructed governance models rely on long-term contracts and further unbundling of electricity grid activities (being electricity transmission and system operation), while one governance model (the TSO model) relies on regulation and bundling of the electricity grid activities. The analysis of these governance models shows that there is no optimal governance model. However, to facilitate the efficient deployment of a MOG, the TSO model is considered most preferable, as this governance model is able to facilitate the gradual development of a MOG, while also facilitating efficient operation by limiting coordination issues that can arise due to unbundling. This model will rely on current owners of the TSOs to provide the necessary investment capital and it remains to be seen whether these owners have the willingness to do so, provided the enormous scale of investments to reach EU climate goals.Systems Engineering, Policy Analysis and Management (SEPAM
Applying Dynamic Damping to Robotic Vitreoretinal Surgery
No full textVitreoretinal surgery remains one of the most challenging types of surgery due to the delicate nature of the eye, the minimally invasive nature of the procedure, the small operating space and lack of depth perception. One of the procedures that is performed during vitreoretinal surgery is Epiretinal Membrane (ERM) Peeling , during which the surgeon has to peel a membrane of the retina without damaging the retina. Robotic membrane peeling can greatly improve clinical outcome because of increased accuracy, tremor reduction and little fatigue effects. However, depth perception remains a problem, because the surgeon is looking at the procedure from directly above through a microscope, therefore creating a 2-D vision. The topic of this study is a tele-operated robotic system that is specialized in vitreoretinal surgery. The PRECEYES surgical system is equipped with an OCT -sensor that can estimate how far away the tip is from the retina, but not accurately enough for traditional 'forbidden region' assistance. This study aims to design and evaluate a proof-of-concept for haptic support during robot-assisted vitreoretinal surgery, by means of an artificial damping-field on the master device. The main contributions of this study were 1) to create a simulation environment for robot-assisted vitreoretinal surgery; 2) to design and implement a damping field on this simulator; and 3) to perform a human-in-the-loop experiment to compare unassisted control behaviour to assisted control behaviour To study the effect of the damping field, a simulation of the procedure was created. A physical haptic master device controls a virtual slave in a simulated environment. The participants (n=16) were asked to move the instrument towards the retina, and then gently move it through a ring on the surface of the retina. This task forced the participant to make a peeling motion that is typical for ERM peeling. The experiment had 4 conditions: a small or a large target, with the damping field switched on or off. Each of the 16 participants had to perform 10 successful runs per condition. A retina puncture resulted in a failure and is not counted as a successful run. Results showed that for the small target, the average number of punctures per participant decreased from 2.4 to 0.9 when the damping field was enabled. The average completion time was comparable for both small target conditions, and likewise for the large target conditions. It was observed that participants decreased their velocity at the same distance of the retina for multiple runs when the damping field was active, which indicates that the participants were able to estimate the distance to the retina using the damping field. Furthermore, the damping field enabled the participants to employ a larger safety margin (distance between the instrument and the retina) between the instrument and the retina. For the experimental conditions studied, the damping field decreased the amount of punctures without affecting the completion time. Improvements to the damping field, such as an exponential increase of the damping coefficient and moving the starting point closer to the retina could increase the performance.<br/
The interplay between metabolic stochasticity and cAMP-CRP regulation in single E. coli cells
Get PDFThe inherent stochasticity of metabolism raises a critical question for understanding homeostasis: are cellular processes regulated in response to internal fluctuations? Here, we show that, in E. coli cells under constant external conditions, catabolic enzyme expression continuously responds to metabolic fluctuations. The underlying regulatory feedback is enabled by the cyclic AMP (cAMP) and cAMP receptor protein (CRP) system, which controls catabolic enzyme expression based on metabolite concentrations. Using single-cell microscopy, genetic constructs in which this feedback is disabled, and mathematical modeling, we show how fluctuations circulate through the metabolic and genetic network at sub-cell-cycle timescales. Modeling identifies four noise propagation modes, including one specific to CRP regulation. Together, these modes correctly predict noise circulation at perturbed cAMP levels. The cAMP-CRP system may thus have evolved to control internal metabolic fluctuations in addition to external growth conditions. We conjecture that second messengers may more broadly function to achieve cellular homeostasis.BN/Sander Tans La
The Role of Demand Response in the Future Electricity System: Implications on market design and the barriers perceived by Dutch non-domestic consumers
No full textNowadays, there is growing consensus, among policy makers and market participants, that Demand Response (DR) is a critical resource for achieving increasing competitiveness and more efficient operation in the electricity system, as well as greater sustainability in the society. When there will be more intermittent energy sources like solar and wind energy in the Dutch electricity system, DR can be one of the cost-efficient solutions for ensuring the security of supply. It is predicted by CE Delft that the need for peak power will increase by 30% in the Netherlands, until 2023.DR is the change in the electricity consumption patterns by the customers in reaction to price signals or to specific requests, with the aims of providing flexibility to the electricity system and meanwhile benefiting from doing so. DR can contribute to system balancing, by the physical influence of load shedding and load shifting. Load shifting involves either shifting electricity use during peak times, or increasing electricity use during off peak times. Load shedding means that the power consumption is irrevocably reduced, which for the industry means lost production. It is found that although most Dutch non-domestic companies are interested in DR, they haven’t investigated much in their DR potential yet. A lot of companies currently see no business cases in DR, because of the current oversupply in flexible energy sources and low electricity prices. Most importantly, some energy consumers (e.g: iron & steel industry, telecommunication industry) have inflexible processes to secure their core business. It is also found that most DR resources come from Small-Medium Enterprises (SMEs). In the Netherlands, first movers among the Dutch non-domestic consumers could be cold stores, water management companies, and greenhouse farmers, due to their flexible consumption processes. However, they perceive huge barriers to implement DR, mainly market complexity, market entry access and transaction costs. A typology of DR programmes in different market segments is summaries in this thesis report, according to previous literatures. However, it is necessary to specify the DR programmes in more detailed levels for practical use in specific national market. In the Dutch electricity market, ETPA and Senfal are two interesting stakeholders who act as enablers to facilitate (automatic) DR behaviour. ETPA as a low-threshold trading platform, serves as a market place to trade DR resources in the electricity short-term markets. They provide bidding portfolios to reduce the market complexity, require the minimum bidding volume of 0.5MW to open more market entry access and offer relatively low membership fee for lowing the transaction costs to SMEs. Meanwhile, Senfal provides knowledge support to consumers, by using intelligent software to optimize their consumption according to the electricity prices. Senfal also represents the typical business mode of Dutch independent aggregators, who cooperation with energy suppliers and provide DR services. The complex barriers need cooperation among market stakeholders to work out with the reliable and cost-beneficial market solutions. TenneT, the Dutch Transmission System Operator (TSO) with regulated tasks, is pro-actively investigating in future solutions, engaging with all the market stakeholders.Systems Engineering, Policy Analysis and Management (SEPAM
Charge Injection, Charge Trapping and Charge Transfer in Quantum-Dot Solids
No full textThis study reports on fundamental processes in Quantum-Dot Solids, after light absorption. Transient Absorption and Time-resolved Photoluminescence spectrocopy reveal the dynamics of charge transfer and charge trapping processes. Typically, both occur on a picosecond time scale and compete with each other. We find that the efficiency of these processes depends on the Fermi level in the Quantum-Dot Solid. The latter can be controlled electrochemically, via charge injection into the Quantum-Dot Solid, using a potentiostat. The presented findings aid the rational design of opto-electronic devices based on Quantum Dots, such as solar cells or LEDs.Chemical EngineeringApplied Science
De vernieuwde gulden winckel der kunstliebende Nederlanders : waer in den mensche door poëtische, historische en morale leeringen, vertoont wort, hoedanigh hy zijn leven, handel ende wandel, zedighlijck, eerbaerlijck en vermakelijck sal overbrengen : hier is by ghevoeght het tweede deel, waer in 't vvelvaren der vereenighde Nederlanden, en de droeve vvtvaert van Henricus de Grote, coningh van Vranckrijck en Navarre, &c. : nessens andere stichtelijcke dinghen, den konst-beminders worden voor oogen ghestelt /
No full textSignatures: A-Y⁴.Page numbers 1-73 appear on both left and right pages of openings with emblematic engraving at left and explanatory verses at right. The 73 engravings are lettered A-T in groups of four (omitting J; group D has 3 engravings and group T has 2). They are by Gerard de Jode after Crispin van den Broeck, and derive from those in Laurens van Haecht Goidtsenhoven's Mikrokosmos (first published 1579); see Landwehr.Roman, italic, gothic and civilité fonts.Printed by Paulus van Rabesteyn. See colophon.First published under title Den gulden winckel in 1613.Landwehr, J. Emblem and fable books (3rd ed.),Mode of access: Internet.Jan Borms' property stamps on back pastedown.Binding: later decorated paper. Author, title & date written on spine. Edges sprinkled red
Ultrafast charge cooling and carrier multiplication in semiconductor nanocrystals and superlattices
No full textWe studied charge carrier photogeneration, cooling, carrier multiplication (CM) and charge mobility and decay in: a) isolated PbSe nanocrystals in solution, b) films of PbSe nanocrystals coupled by organic ligands, and c) 2D percolative networks of epitaxially connected PbSe nanocrystals. The studies were performed using ultrafast pump-probe spectroscopy with optical or terahertz/microwave conductivity detection. The effects of electronic coupling between the nanocrystals on charge mobility were characterized by frequency-resolved microwave and terahertz photoconductivity measurements. Reducing the size of ligand molecules between nanocrystals in a film strongly increases the charge mobility. Direct connection of nanocrystals in a percolative network yielded a sum of electron and hole mobilities as high as 270±10 cm2V-1s-1. We found that a high mobility is essential for multiple electron-hole pairs formed via CM to escape from recombination. The coupling between the nanocrystals was found to strongly affect the competition between cooling of hot charges by phonon emission and CM. In percolative networks of connected nanocrystals CM is much more efficient than in films with ligands between the nanocrystals. In the e networks CM occurs in a step-like fashion with threshold near the minimum photon energy of twice the band gap.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.ChemE/Opto-electronic MaterialsTU Delft Librar
Noncooperative household consumption with caring
Get PDFWe present a household consumption model that accounts for caring household members, while allowing for noncooperative behavior in decisions on public goods. The intrahousehold consumption outcome critically depends on the degree of caring between the household members. By varying the degree of intrahousehold caring, the model encompasses a whole continuum of household consumption models that are situated between the fully cooperative model and the noncooperative model without caring. This feature is used to define a measure for the degree of cooperation within the household. We also establish a dual characterization of our noncooperative model with caring preferences: we show that the model is dually equivalent to a noncooperative model with non-caring preferences that is characterized by intrahousehold transfers. Finally, following a revealed preference approach, we derive testable implications of the model for empirical data. We demonstrate the practical usefulness of the model through an illustrative application.
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