6,568 research outputs found

    Increased lifetime of Organic Photovoltaics (OPVs) and the impact of degradation, efficiency and costs in the LCOE of Emerging PVs

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    Emerging photovoltaic (PV) technologies such as organic photovoltaics (OPVs) and perovskites (PVKs) have the potential to disrupt the PV market due to their ease of fabrication (compatible with cheap roll-to-roll processing) and installation, as well as their significant efficiency improvements in recent years. However, rapid degradation is still an issue present in many emerging PVs, which must be addressed to enable their commercialisation. This thesis shows an OPV lifetime enhancing technique by adding the insulating polymer PMMA to the active layer, and a novel model for quantifying the impact of degradation (alongside efficiency and cost) upon levelized cost of energy (LCOE) in real world emerging PV installations. The effect of PMMA morphology on the success of a ternary strategy was investigated, leading to device design guidelines. It was found that either increasing the weight percent (wt%) or molecular weight (MW) of PMMA resulted in an increase in the volume of PMMA-rich islands, which provided the OPV protection against water and oxygen ingress. It was also found that adding PMMA can be effective in enhancing the lifetime of different active material combinations, although not to the same extent, and that processing additives can have a negative impact in the devices lifetime. A novel model was developed taking into account realistic degradation profile sourced from a literature review of state-of-the-art OPV and PVK devices. It was found that optimal strategies to improve LCOE depend on the present characteristics of a device, and that panels with a good balance of efficiency and degradation were better than panels with higher efficiency but higher degradation as well. Further, it was found that low-cost locations were more favoured from reductions in the degradation rate and module cost, whilst high-cost locations were more benefited from improvements in initial efficiency, lower discount rates and reductions in install costs

    The Adirondack Chronology

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    The Adirondack Chronology is intended to be a useful resource for researchers and others interested in the Adirondacks and Adirondack history.https://digitalworks.union.edu/arlpublications/1000/thumbnail.jp

    Varastest embrüotest pärit ekstratsellulaarsed vesiikulid: potentsiaal embrüokvaliteedi markeritena ja roll embrüo-emaka suhtluses

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    Väitekirja elektrooniline versioon ei sisalda publikatsiooneViljatus on globaalne rahvatervise probleem, mis mõjutab miljoneid inimesi. Abistav reproduktiivtehnoloogia, sealhulgas in vitro viljastamine, on aidanud mitmeid viljatuid inimesi. Küll on sellel metoodikal üheks kitsaskohaks implantatsiooni ebaõnnestumine isegi morfoloogiliselt parimate embrüotega. Seetõttu toimuvad jätkuvalt uuringud tuvastamaks paremaid meetodeid, mis hindavad embrüo kvaliteeti ja ennustavad siirdamise edukust, olles peamiselt embrüokasvusöötme baasil. Rakuvälised ehk ekstratsellulaarsed vesiikulid (EV) on membraaniga ümbritsetud nanoosakesed, mida toodavad peaaegu kõik rakutüübid erinevates füsioloogilistes ja patoloogilistes konditsioonides. Nende kaudu toimub rakuvaheline suhtlus. Mitmed uuringud, eriti vähi korral, on uurinud EVde potentsiaali biomarkerina ja ravimkandursüsteemina. Antud doktoritöö uuris implantatsiooni-eelse perioodi embrüost vabanenud EVde potentsiaali embrüokvaliteedi markerina ja embrüo-emaka suhtluse vahendajana. Katsed viidi läbi kasutades veise-embrüoid ja inimrakukultuuride põhiseid eksperimentaalmudeleid. Esimene uuring tõestas, et individuaalselt kasvatatud implantatsiooni-eelse perioodi veise-embrüod eritavad EVsid kasvusöötmesse ning nende kontsentratsiooni- ja suurusprofiil sõltub embrüo kvaliteedist ja arengustaadiumist. Järgnevalt katsetati munajuharakkudel implantatsiooni-eelse perioodi embrüost pärit EVde funktsionaalsust. Katse käigus selgus, et EVd kõrge kvaliteediga embrüotest muutsid munajuharakkude geeniekspressiooni, mida aga ei teinud halva kvaliteediga embrüote EVd. Suurenenud ekspressiooniga geenide hulgas olid mitmed interferoon-τ raja interferooni stimuleerivad geenid. Interferoon-τ peetakse mäletsejaliste tiinuse tuvastusmolekuliks. See leid viitab, et munajuha tunneb ära kvaliteetse embrüo. Viimaseks uuriti embrüo EVde funktsionaalsuse spetsiifilisust. Leiti, et endomeetrium reageerib vaid embrüo päritolu EVdele. Uuringute käigus tuvastati embrüost vabanenud EVde potentsiaal ja spetsiifilisus embrüokvaliteedi biomarkerina.Infertility is a global public health problem that affects millions of people in their reproductive life. Assisted reproductive technologies (ARTs) such as in-vitro fertilization have enabled many patients to overcome this issue. However, a bottleneck in ART success is the implantation failure even after the transfer of morphologically best embryos. Hence, investigations continue to identify better or complementary methods of assessing embryo quality and predicting transfer success, mainly based on the embryo culture media. Extracellular vesicles (EVs) are membrane-bound nanoparticles released by almost all types of cells under different physiological and pathological conditions. They mediate intercellular communication. Many studies, especially related to cancer, have investigated EVs' potential as biomarkers and therapeutic drug delivery systems. This project investigated preimplantation embryo-derived extracellular vesicles as a potential embryo quality marker and a mediator of embryo-maternal communication. Experiments were performed using bovine embryos and human cell-culture based experimental models. The first study showed that individually cultured preimplantation bovine embryos release EVs to their culture media, and their concentration and size profile are dependent on the quality and development stage of embryos. Subsequently, the functionality of preimplantation embryo-derived EVs were tested in the oviduct. It was observed that EVs from good quality embryos, but not the EVs from embryos of low developmental potential quality, could alter the gene expression of the oviduct. Among the up-regulated genes, many were interferon-stimulated genes of the interferon-τ pathway. Interferon-τ is considered the pregnancy recognition molecule in ruminant pregnancy. This finding suggests that the oviduct can serve as a biosensor of embryo quality. Finally, the functional specificity of embryonic EVs were investigated. It was observed that endometrium only react to embryonic EVs but not to the non-embryonic EVs. All these studies support the potential and specificity of embryo-derived EVs as a biomarker of embryo quality.https://www.ester.ee/record=b548409

    Models for spin-dependent transport in helical molecules

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    Chiral molecules act as strong spin filters for transmitted electrons (chiral-induced spin selectivity). The interplay of geometry and spin mediated by spin-orbit coupling is commonly assumed as the cause of the effect, but the theoretical description remains incomplete. In this thesis, two models for electron transport through helical molecules were investigated: an atomistic tight binding model for the molecule helicene and a simple continuum model for an electron in a helix-shaped potential. In an attempt to cover the middle ground between phenomenological tight binding approaches and detailed first principle simulations, the helicene model starts with a lattice of carbon atoms represented by a minimal basis of local atomic s- and p-orbitals including electronic nearest-neighbor and spin-orbit interactions. Löwdin partitioning is used to reduce the model to a p-orbital tight binding representation, providing numeric values for all the couplings dependent on geometry. Transport calculations showed helicity dependent spin polarization several orders of magnitude smaller than experimentally observed. To understand the effect on a more fundamental level, an electron moving through a helix-shaped confinement potential in 3D space with spin-orbit coupling was considered. By taking the limit of strong confinement, an approximate model with one-dimensional configuration space (the helix) was obtained. Novel onsite spin-orbit coupling terms appear in the effective Hamiltonian, leading to sizeable spin polarization in transport calculations. These new terms are thoroughly justified by the adiabatic limiting procedure which was adapted to include spin-orbit coupling and might thus provide one of the missing pieces for the theory of chiral-induced spin selectivity

    Flexographic printed nanogranular LBZA derived ZnO gas sensors: Synthesis, printing and processing

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    Within this document, investigations of the processes towards the production of a flexographic printed ZnO gas sensor for breath H2 analysis are presented. Initially, a hexamethylenetetramine (HMTA) based, microwave assisted, synthesis method of layered basic zinc acetate (LBZA) nanomaterials was investigated. Using the synthesised LBZA, a dropcast nanogranular ZnO gas sensor was produced. The testing of the sensor showed high sensitivity towards hydrogen with response (Resistanceair/ Resistancegas) to 200 ppm H2 at 328 °C of 7.27. The sensor is highly competitive with non-catalyst surface decorated sensors and sensitive enough to measure current H2 guideline thresholds for carbohydrate malabsorption (Positive test threshold: 20 ppm H2, Predicted response: 1.34). Secondly, a novel LBZA synthesis method was developed, replacing the HMTA by NaOH. This resulted in a large yield improvement, from a [OH-] conversion of 4.08 at% to 71.2 at%. The effects of [OH-]/[Zn2+] ratio, microwave exposure and transport to nucleation rate ratio on purity, length, aspect ratio and polydispersity were investigated in detail. Using classical nucleation theory, analysis of the basal layer charge symmetries, and oriented attachment theory, a dipole-oriented attachment reaction mechanism is presented. The mechanism is the first theory in literature capable of describing all observed morphological features along length scales. The importance of transport to nucleation rate ratio as the defining property that controls purity and polydispersity is then shown. Using the NaOH derived LBZA, a flexographic printing ink was developed, and proof-of-concept sensors printed. Gas sensing results showed a high response to 200 ppm H2 at 300 °C of 60.2. Through IV measurements and SEM analysis this was shown to be a result of transfer of silver between the electrode and the sensing layer during the printing process. Finally, Investigations into the intense pulsed light treatment of LBZA were conducted. The results show that dehydration at 150 °C prior to exposure is a requirement for successful calcination, producing ZnO quantum dots (QDs) in the process. SEM measurements show mean radii of 1.77-2.02 nm. The QDs show size confinement effects with the exciton blue shifting by 0.105 eV, and exceptionally low defect emission in photoluminescence spectra, indicative of high crystalline quality, and high conductivity. Due to the high crystalline quality and amenity to printing, the IPL ZnO QDs have numerous potential uses ranging from sensing to opto-electronic devices

    Synthese und Optimierung von Konstruktionsbäumen aus unstrukturierten räumlichen Daten

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    Sensorsysteme für die dreidimensionale Abtastung von Objektoberflächen sind in vielen Bereichen des täglichen Lebens omnipräsent. Moderne Smartphones und Spielekonsolen im Heimanwenderbereich sowie professionelle Systeme, z.B. eingesetzt zur Qualitätssicherung in Fertigungsprozessen, beinhalten Hard- und Softwarekomponenten zur Ermittlung räumlicher Daten. Aus entsprechenden Quellen stammende Datensätze bestehen meist aus einzelnen dreidimensionalen Punkten, die in unstrukturierter Form und potentiell messfehlerbehaftet vorliegen. Oft ist die Erzeugung dieser Punktwolke nur der erste Schritt innerhalb eines komplexen Verarbeitungsprozesses, an dessen Ende eine Repräsentation der räumlichen Daten steht, die für den entsprechenden Anwendungsfall als optimal angesehen wird. Ein solcher Anwendungsfall ist z.B. die automatische Erzeugung von Architekturplänen oder das Reverse Engineering (RE), also die Analyse des Aufbaus und der Funktionsweise eines Produkts. In beiden Fällen ist eine Repräsentation von Vorteil, die unnötige Details abstrahiert und dabei weiterführende Information über den Aufbau des Objekts und dessen elementare Bausteine beinhaltet. Eine solche Darstellung ist die sog. Constructive Solid Geometry (CSG)-Repräsentation, die Modelle als Baumstruktur bestehend aus Booleschen Mengenoperatoren in den inneren Knoten und geometrischen Primitiven in den äußeren Knoten beschreibt. Dabei ist die manuelle Erzeugung dieses sog. Konstruktionsbaums (KB) aus einer Punktwolke zeitaufwendig und für komplexe Datensätze kaum zu bewerkstelligen. Aus diesem Grund werden in dieser Arbeit Methoden vorgestellt, die das Problem der automatischen Synthese von KBs aus fehlerbehafteten Punktwolken robust und effizient lösen. Die vorgestellten Verfahren werden dabei in eine eigens entwickelte Prozess-Pipeline eingebettet und miteinander verknüpft. Den Anfang macht die Einführung eines Systems, das geometrische Primitive, wie Kugeln, Zylinder und allgemeine konvexe Polytope, mittels Maschinellem Lernen (ML) und Evolutionären Algorithmen (EA) in der Eingabepunktwolke detektiert und in diese einpasst. Dieser folgt die Vorstellung einer Methode, die das eigentliche KB-Syntheseproblem für bekannte Primitive löst und dazu auf graphbasierte Partitionierungs- und Vereinfachungsstrategien zur Steigerung von Laufzeiteffizienz und Robustheit zurückgreift. Da die Repräsentation als KB nicht eindeutig ist, lassen sich zusätzliche Metriken, wie z.B. die Baumgröße, bestimmen und existierende KBs entsprechend optimieren. Dieses Problem steht abschließend im Fokus dieser Arbeit, zu dessen vorgestellter Lösung ein Spektrum unterschiedlicher Lösungsstrategien evaluiert und diskutiert wird.Sensor systems for three-dimensional object surface scanning are omnipresent in many areas of daily life. Modern smartphones and game consoles for home users and professional systems, e.g., used for quality assurance in manufacturing processes, contain hard- and software components for measuring spatial data. Data sets originating from such sources usually consist of individual three-dimensional points which are unstructured and potentially subject to measurement errors. Often, the generation of this so-called point cloud is only the first step within a complex processing procedure which results in a spatial data representation that is considered optimal for a specific use case. Such a use case is, for example, the automatic generation of architectural plans or Reverse Engineering (RE), i.e., the analysis of a product's structure and functionality without any prior knowledge. In both cases, it is advantageous to obtain a representation that abstracts unnecessary details while providing more information about an object's structure and elementary building blocks. Such a representation is called Constructive Solid Geometry (CSG), which describes models as a tree structure consisting of Boolean set operators in the inner nodes and geometric primitives in the outer nodes. However, the manual generation of these so-called Construction Trees (CTs) based on a measured point cloud is time-consuming and hardly feasible for complex data sets. For this reason, this work presents methods that can robustly and efficiently solve the problem of automatically synthesizing CTs from error-prone point clouds. The presented methods are thereby embedded and interconnected in a newly developed process pipeline. At first, a system is introduced that detects and fits geometric primitives such as spheres, cylinders and general convex polytopes in the input point cloud using Machine Learning (ML) and Evolutionary Algorithms (EA). This is followed by an introduction of a method that solves the automatic CT synthesis problem for known primitives using graph-based partitioning and simplification strategies to increase runtime efficiency and robustness. Since the representation as CTs is not unique additional metrics such as tree size can be determined, and existing CTs can be optimized accordingly. This problem is the last this work addresses for which a spectrum of different solution strategies is evaluated and discussed

    Motion patterns of subviral particles: Digital tracking, image data processing and analysis

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    At the Institute of Virology, Philipps-University, Marburg, Germany, currently research on the understanding of the transport mechanisms of Ebola- and Marburgvirus nucleocapsids is carried out. This research demands a profound knowledge about the various motion characteristics of the nucleocapids. The analysis of large amounts of samples by conventional manual evaluation is a laborious task and does not always lead to reproducible and comparable results. In a cooperation between the Institute of Virology, Marburg, and the Institute for Biomedical Engineering, University of Applied Sciences, Giessen, Germany, algorithms are developed and programmed that enable an automatic tracking of subviral particles in fluorescence microscopic image sequences. The algorithms form an interface between the biologic and the algorithmic domain. Furthermore, methods to automatically parameterize and classify subviral particle motions are created. Geometric and mathematical approaches, like curvature-, fractal dimension- and mean squared displacement-determination are applied. Statistical methods are used to compare the measured subviral particle motion parameters between different biological samples. In this thesis, the biological, mathematical and algorithmic basics are described and the state of the art methods of other research groups are presented and compared. The algorithms to track, parameterize, classify and statistically analyze subviral particle tracks are presented in the Methods section. All methods are evaluated with simulated data and/or compared to data validated by a virologist. The methods are applied to a set of real fluorescence microscopic image sequences of Marburgvirus infected live-cells. The Results chapter shows that subviral particle motion can be successfully analyzed using the presented tracking and analysis methods. Furthermore, differences between the subviral particle motions in the analyzed groups could be detected. However, further optimization with manually evaluated data can improve the results. The methods developed in this project enhance the knowledge about nucleocapsid transport and may be valuable for the development of effective antiviral agents to cure Ebola- and Marburgvirus diseases. The thesis concludes with a chapter Discussion and Conclusions

    Radiant Energy Spectrum Converters for Solar Energy Harvesting

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    Solar energy is a particularly attractive form of renewable energy because it is widely available and the amount of solar energy received on Earth each year is ~3.5 x 10^6 EJ, which is more than 7000 times greater than the annual global energy consumption. However, solar energy remains largely untapped because it is a broadband, intermittent and sparse resource, making it difficult to harness. Herein, the implementation of newly designed optical cavities, referred to as Radiant Energy Spectrum Convertors (RESC), in the form of ellipsoids, spheroids and/or paraboloids is presented for broadband solar energy harvesting and conversion applications. In this thesis RESC structures are designed and their application in four broadband solar energy harvesting applications is numerically analyzed: 1) photobioreactors, 2) agri-voltaics, 3) hybrid solar lighting, and 4) Solar Thermophotovoltaics (STPV). 1) The RESC structure in the photobioreactor is a luminescent solar spectrum splitter that partitions the solar irradiance into photosynthetically active radiation (PAR) and photosynthetically inactive radiation (non-PAR) to simultaneously power algae cultivation systems and PV cells, respectively. Results show that a RESC structure enables 0.25 MJ of electric power generation in a photobioreactor with a projected area of and volume of 0.2 m^2 and 0.2 m^3, respectively. 2) The RESC structure implemented in agri-voltaics is an elliptic array luminescent solar concentrator for combined power generation and microalgae growth with the similar concept of partitioning solar irradiance into its PAR and non-PAR components. Considering the combined effects of emission, transmission and surface scattering losses, numerical results show the optical efficiency of the elliptic array luminescent solar concentrator (LSC) is 63%, whereas in comparison the optical efficiency for a conventional planar LSC of the same size is 47.2%. 3) The RESC structures used in hybrid solar lighting applications are based on luminescent solar spectrum splitters that partition the incoming solar irradiance into its visible and non-visible components to simultaneously power fibre optic lighting system and PV cells, respectively. Numerical analysis shows that the non-visible portion of the solar irradiance can be converted to electricity with an efficiency of 13.4% using a double-junction PV cell within a RESC structure. 4) RESC structures implemented into STPV systems are based on highly specular IR reflective optical cavities in the form of oblate and prolate spheroid structures to enhance the power density and photoconversion efficiency of the STPV systems. The optical cavity partially encloses a solar receiver that is located at the focal point of an ellipsoid/paraboloid. Concentrated solar radiation is absorbed by the receiver, which functions as both an absorber and an emitter. Radiation is emitted from the emitter, and the internal surface of the cavity is able to reflect a large portion of this emitted radiation either back to the emitter or to a PV cell. Emitted radiation that is returned to the emitter is referred to as "photon recycling". A high degree of photon recycling can be used to achieve high emitter temperatures, which enhances the performance of STPV systems. The results presented in this thesis show that optical structures in the form of spheroids and paraboloids can be used to partition, control and harness broadband solar energy to simultaneously provide for multiple applications, which ultimately increases overall solar energy conversion efficiencies
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