Charge Storage mechanisms and interactions of hybrid supercapacitor electrode materials with next-generation electrolytes

The storage of electrical energy is of outmost importance in today’s society for a wide range of applications. Batteries, that are most common for electrical energy storage today, struggle with low power density and limited cycle lifetime. As an alternative to batteries, supercapacitors have a high-power density and almost unlimited cycle lifetime. However, the lower energy content of supercapacitors limits their use in different applications.\ua0Two properties determine the energy content of supercapacitors: the capacity of the electrodes and operating voltage of the device. Metal oxides have a high capacity compared to standard carbon electrodes. In this thesis MnO2, VO2\ua0and TiO2\ua0are investigated together with novel electrolytes. Previously these materials have been mostly studied in standard aqueous electrolytes. Ionic liquids (ILs) is a class of novel solvents which can be more stable than aqueous electrolytes and mitigate problems associated with organic electrolytes. Another electrolyte concept receiving increasing interest is highly concentrated electrolytes (HCEs) in which the high salt concentration makes the electrolyte electrochemically stable. The electrode-electrolyte interaction is governed by the properties of the choice of electrolyte but also the morphology of the electrodeIn this work I present findings that could facilitate the development of next-generation hybrid supercapacitors with improved energy density as a result of high-capacity electrodes and novel electrolytes. By choosing appropriate electrolytes a higher capacity of the electrode could be obtained together with an increased voltage window, increasing the energy density further. I also present findings regarding the morphology and structure of the electrode. Examples of new findings include the role of protic ionic liquids in the charge-storage mechanism of MnO2, which enables redox reactions in the absence of Li-ions. The mitigation of the capacity fade in TiO2 microbeads through the interaction with an ionic liquid electrolyte

Novel electrolytes for next-generation hybrid supercapacitors - Investigating the interaction between electrolyte and electrode

The storage of electrical energy is of outmost importance in today’s society, ranging from cell phones to large scale energy\ua0storage of intermittent electricity sources. Batteries, that are most commonly used, struggle with low power density and limited\ua0cycle lifetime. Supercapacitors are seen as an alternative to batteries with their high-power density and almost unlimited cyclelifetime. However, supercapacitors only use the surface of the electrode which reduces the energy content compared to batteries.\ua0The low energy density limits their use in different applications where they otherwise would have been suitable. To increase\ua0the energy density metal oxides, such as MnO2, RuO or VO2, with higher energy content than carbon are often added to the\ua0electrodes. The total energy is also proportional to the voltage window, squared, in which the device operates. The normal\ua0limiting factor of the voltage window is the electrolyte, all electrolytes breaks down if polarized to sufficiently high or low\ua0potentials. Choosing an electrolyte with a large voltage window will also increase the energy content of the cell.\ua0This thesis focuses on combining these two approaches to increase the energy density even further by investigating novel, highenergy,\ua0electrolytes and their interactions with MnO2 and VO2 based electrodes. Electrochemical measurements and physical\ua0characterization of the electrolytes are used to determine important parameters for optimal performance of the electrodes. Theresults show that by using protic ionic liquids the contribution of MnO2-electrodes to the total energy content can be increased\ua0while the potential window is widened. Highly-concentrated aqueous NaTFSI electrolytes present a promising, cheap,\ua0alternative with a larger potential window compared to standard aqueous electrolytes. VO2-electrodes performs well but with\ua0a limited cycle lifetime in the NaTFSI electrolyte and have higher energy density combined with retained power density

Exciting Neutron-rich Nuclei

Atoms are the building blocks which make up our world. Their stability depends on the atomic nucleus, consisting of protons and neutrons.Nuclei are complex many-body quantum mechanical systems governed by the nucleon-nucleon interaction. The complexity and the intricate nature of the nucleon-nucleon interaction so far prevented the description of all existing nuclei by a single model. Furthermore, nuclei and nuclear reactions in stars and stellar explosions play a key role in astrophysics. This motivates experiments to improve our understanding of nuclei and their role in the cosmos.In this thesis I present results from experiments in complete kinematics performed at the radioactive beam facilities RIKEN and GSI/FAIR. The focus is on the rst measurement of unbound states in 29Ne, that were studied using neutron knockout reactions from 30Ne. The invariant-mass spectrum shows two peaks, one at around 0.5 MeV and another one at 1.3 MeV. Moreover, results from an overview experiment, investigating light neutron-rich nuclei, between 3 < Z < 10, are also presented. The results cover protonremoval cross sections in boron and carbon, important for designing future experiments, and unbound states in 26F where the rst unbound states are observed at the relative energy 323 keV. Furthermore, the structure of the unbound nucleus 13Be, which is important for its bridging role between the bound 12Be and the Borromean halo nucleus 14Be, is studied. Also measurements on Coulomb dissociation of 20;21N and 18C are presented which allow to improve our understanding of r-process nucleosynthesis

Microbial production of next-generation stevia sweeteners

BACKGROUND: The glucosyltransferase UGT76G1 from Stevia rebaudiana is a chameleon enzyme in the targeted biosynthesis of the next-generation premium stevia sweeteners, rebaudioside D (Reb D) and rebaudioside M (Reb M). These steviol glucosides carry five and six glucose units, respectively, and have low sweetness thresholds, high maximum sweet intensities and exhibit a greatly reduced lingering bitter taste compared to stevioside and rebaudioside A, the most abundant steviol glucosides in the leaves of Stevia rebaudiana. RESULTS: In the metabolic glycosylation grid leading to production of Reb D and Reb M, UGT76G1 was found to catalyze eight different reactions all involving 1,3-glucosylation of steviol C (13)- and C (19)-bound glucoses. Four of these reactions lead to Reb D and Reb M while the other four result in formation of side-products unwanted for production. In this work, side-product formation was reduced by targeted optimization of UGT76G1 towards 1,3 glucosylation of steviol glucosides that are already 1,2-diglucosylated. The optimization of UGT76G1 was based on homology modelling, which enabled identification of key target amino acids present in the substrate-binding pocket. These residues were then subjected to site-saturation mutagenesis and a mutant library containing a total of 1748 UGT76G1 variants was screened for increased accumulation of Reb D or M, as well as for decreased accumulation of side-products. This screen was performed in a Saccharomyces cerevisiae strain expressing all enzymes in the rebaudioside biosynthesis pathway except for UGT76G1. CONCLUSIONS: Screening of the mutant library identified mutations with positive impact on the accumulation of Reb D and Reb M. The effect of the introduced mutations on other reactions in the metabolic grid was characterized. This screen made it possible to identify variants, such as UGT76G1(Thr146Gly) and UGT76G1(His155Leu), which diminished accumulation of unwanted side-products and gave increased specific accumulation of the desired Reb D or Reb M sweeteners. This improvement in a key enzyme of the Stevia sweetener biosynthesis pathway represents a significant step towards the commercial production of next-generation stevia sweeteners. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1186/s12934-016-0609-1) contains supplementary material, which is available to authorized users

Electrochemical Behaviour of Nb-Doped Anatase TiO2 Microbeads in an Ionic Liquid Electrolyte

TiO(2)is a promising material for high-power battery and supercapacitor applications. However, in general TiO(2)suffers from an initial irreversible capacity that limits its use in different applications. A combination of a microbead morphology, Nb-doping, and the use of an ionic liquid electrolyte is shown to significantly decrease the irreversible capacity loss. A change in the electrochemical response in the first cycles indicates formation of a solid-electrolyte interphase (SEI) or a modification of the structure of the surface layer of the TiO2/Nb microbeads, which apparently stabilises the performance. The change in the response is manifested in an increased charge transfer resistance and the presence of two charge transfer contributions. During prolonged cycling the TiO2/Nb electrode shows an excellent stability over 5000 cycles. Ex situ analysis after cycling shows that the overall microbead morphology is intact and that there are no changes in the crystal structure. However, a decrease in the intensity of the XRD pattern can point to a decrease in size of the nanocrystals building up the microbeads or the formation of amorphous phases

Writ(h)ing Images: Imagination, the Human Form, and the Divine in William Blake, Salman Rushdie, and Simon Louvish

In this paper, we address issues in segmentation Of remotely sensed LIDAR (LIght Detection And Ranging) data. The LIDAR data, which were captured by airborne laser scanner, contain 2.5 dimensional (2.5D) terrain surface height information, e.g. houses, vegetation, flat field, river, basin, etc. Our aim in this paper is to segment ground (flat field)from non-ground (houses and high vegetation) in hilly urban areas. By projecting the 2.5D data onto a surface, we obtain a texture map as a grey-level image. Based on the image, Gabor wavelet filters are applied to generate Gabor wavelet features. These features are then grouped into various windows. Among these windows, a combination of their first and second order of statistics is used as a measure to determine the surface properties. The test results have shown that ground areas can successfully be segmented from LIDAR data. Most buildings and high vegetation can be detected. In addition, Gabor wavelet transform can partially remove hill or slope effects in the original data by tuning Gabor parameters

MCRB-based Performance Analysis of 6G Localization under Hardware Impairments

Location information is expected to be the key to meeting the needs of communication and context-aware services in 6G systems. User localization is achieved based on delay and/or angle estimation using uplink or downlink pilot signals. However, hardware impairments (HWIs) distort the signals at both the transmitter and receiver sides and thus affect the localization performance. While this impact can be ignored at lower frequencies where HWIs are less severe, modeling and analysis efforts are needed for 6G to evaluate the localization degradation due to HWIs. In this work, we model various types of impairments and conduct a misspecified Cram\ue9r-Rao bound analysis to evaluate the HWI-induced performance loss. Simulation results with different types of HWIs show that each HWI leads to a different level of degradation in angle and delay estimation performance

MCRB-based Performance Analysis of 6G Localization under Hardware Impairments

Location information is expected to be the key to meeting the needs of communication and context-aware services in 6G systems. User localization is achieved based on delay and/or angle estimation using uplink or downlink pilot signals. However, hardware impairments (HWIs) distort the signals at both the transmitter and receiver sides and thus affect the localization performance. While this impact can be ignored at lower frequencies where HWIs are less severe, modeling and analysis efforts are needed for 6G to evaluate the localization degradation due to HWIs. In this work, we model various types of impairments and conduct a misspecified Cram\ue9r-Rao bound analysis to evaluate the HWI-induced performance loss. Simulation results with different types of HWIs show that each HWI leads to a different level of degradation in angle and delay estimation performance