MSCAGR (Plant Production) / Department of Plant Production / Indigenous trees play important roles in livelihoods for rural communities. Sclerocarya birrea and Berchemia discolor are indigenous in Africa and are used in rural communities for food and livestock feed, as well as for medicinal and construction purposes. These trees are subject to attack by insects, which can result in lower tree productivity. However, there is no documented information about insects found on both tree species in South Africa. This study investigated the seasonal abundance and diversity of insects on S. birrea and B. discolor in Tshikundamalema Area, Limpopo Province, South Africa. Five trees were selected for each of the two tree species at two sampling sites with different vegetation cover, one site mainly the woodland bushveld while the other site was savannah grasslands. Canopy fogging was used to sample insects. Insect samples were collected at one time point for each of the seasons: summer (February), autumn (May), winter (July) and spring (November). Insects were identified to morphospecies and Simpson’s diversity index was used to compare insect diversity on both trees. Analysis of variance was used to compare the abundance of insects across seasons. The most abundant insects were collected from Coleoptera, followed by Hemiptera, Hymenoptera, Diptera, Lepidoptera and Orthoptera. A total of 3259 insects belonging to the six Orders were collected. All specimens belonging to Coleoptera, Hemiptera and Hymenoptera (3216 in total) were identified to Family level, with a total of 97 morphospecies, belonging to 19 Families. Insects from Diptera, Lepidoptera and Orthoptera were not identified further due to their low numbers. The abundance and diversity of insects were affected by seasons, sites and tree species. The number of insects was high during the spring season with 1782 insects, and summer coming second with 1104 individuals, followed by autumn (238 insects), then winter (92). B. discolor sampled for a great number of insects (1741) as compared to S. birrea (1475). The woodland bushveld (1924 insects) surpassed the savannah grassland (1292 insects) site in terms of the insect numbers sampled. / NRF

Die vorliegende Dissertation befasst sich mit der ramanspektroskopischen Charakterisierung von Galliumnitrid (GaN). Der Zusammenhang zwischen Waferkrümmung und mechanischer Restspannungen wird diskutiert. Mit Hilfe konfokaler Mikro-Ramanmessungen wurden Dotierprofile nachgewiesen sowie die Ladungsträgerkonzentration und -beweglichkeit ermittelt. Sämtliche Ramantensorelemente von wz-GaN wurden erstmals durch die Anwendung verschiedener Streugeometrien bestimmt. Eine neu entwickelte Vorwärtsstreuanordnung ermöglichte die Beobachtung von Phonon-Polaritonen. Es konnte gezeigt werden, dass von der theoretischen und experimentellen Betrachtung der Ramanstreuintensitäten dieser Elementaranregungen eindeutig das Vorzeichen der Faust-Henry-Koeffizienten von wz-GaN abgeleitet werden kann. Im Rahmen dieser Arbeit wurden alle Faust-Henry-Koeffizienten für GaN experimentell bestimmt. / This thesis focuses on special aspects of the Raman spectroscopical characterization of wurtzite gallium nitride (wz-GaN). The correlation between wafer curvature and residual stress is discussed. By means of confocal micro-Raman measurements doping profiles were detected as well as the density and mobility of free charge carriers were deduced. All Raman scattering cross sections of wz-GaN were determined the first time using different scattering configurations. A novel method for near-forward scattering was developed in order to observe phonon polaritons with pure symmetry. It is shown that the theoretical and experimental consideration of the Raman scattering efficiency of these elementary excitations allow for determining the sign of the Faust-Henry coefficients of wz-GaN unambiguously. The Faust-Henry coefficients of GaN were deduced from Raman scattering efficiencies of corresponding TO and LO phonons.

In conventional wastewater treatment plants, methanol, ethanol, and acetate are used as carbon source for the denitrification process in the biological nutrient removal. However, growing concern regarding economical costs and carbon footprints from the fossil-based production of these chemicals have forced the companies to look for other alternatives. VFAs have shown a great potential in replacing the conventionally used carbon sources. If implemented this will result in lower chemical cost and a drastic decrease in carbon footprint as well as striving WWTPs towards sustainable development. In this work denitrification has been analysed using different variations of VFAs such as fermented potato protein liquor, food waste and chicken manure VFA. This was done using a basic laboratory setup of a denitrification reactor which used basic stirring agitation and nitrogen purging to ensure anoxic conditions. Nutrients and excess sCOD were added to ensure the highest denitrification rates. The denitrifying biomass was collected at Gryaab AB in the form of k1-carriers making this process a MBBR. The most influential characteristic of the VFAs is the distribution of the acids in the VFA effluent. Butyric acid along with caproic acid showed the best potential for efficient denitrification. The possibility of concentration of VFA effluent showed a high potential when using a nanofiltration system. A C/N ratio of 4.5 conventionally used when methanol is added showed to be the most optimal condition for VFA addition. The combination of VFAs together with conventional used carbon sources showed the best potential in denitrification efficiency proving to be as good or even better than pure synthetic ones. VFAs effluents showed the best potential in removing the intermediate nitrite from the wastewater at high rates. Overall, VFAs shown a great potential for replacing conventionally used carbon sources, demonstrating the potential of substitution, which if implemented will result in lower carbon footprint and a strive towards sustainable development.

С помощью оборудования National Instruments реализованы две установки для нанесения органических покрытий. Установка термовакуумного нанесения с виртуальным прибором «ThermoVac» позволяет производить линейный нагрев испаряемого вещества с фиксированной скоростью до заданной температуры термостатирования в диапазоне от комнатной до 500 °C. Установка для нанесения методом центрифугирования с ВП «SC_organic» позволяет поддерживать заданную скорость вращения подложки в диапазоне от 500 до 9000 об/мин. На базе микрозондовой станции Cascade Microtech MPS150 разработан автоматизированный канал для тестирования мемристорных структур, в режиме многократного чтения и записи. ВП «RW MIM» формирует на выходе SMU источника последовательность импульсов заданной амплитуды и длительности в режимах запись/чтение. Выполнено нанесение и аттестация пленок 5,11-диметил-5,11-дигидроиндоло [3.2-b]карбазола и 5,11-дигексил-5,11-дигидроиндоло[3.2-b]карбазола. По измеренным вольтамперным характеристикам получено, что полупроводник в синтезированных структурах TiN/DMICZ/Au, Ti/DMICZ/Au обладает дырочной проводимостью с подвижностью μ = 4.9∙10-7 см2/(В∙с). Показано, что регистрируемая ВАХ характеризуется петлями гистерезиса, которые свидетельствуют о наличии мемристивного эффекта в образцах TiN/DHICZ/Au. Произведено тестирование исследуемых слоистых структур в режимах многократного чтения/записи. / An automated installation based on National Instruments equipment, two installations for applying organic coatings are implemented. The installation of a thermo vacuum evaporation with a virtual device "ThermoVac" allows linear heating of the evaporated substance at a fixed rate of up to 500 ° C. The centrifugal centrifugation unit with an VI “SC_organic” supports the specified rotation speed of the substrate in the range of 500 to 9000 rpm. Based on the microprobe station Cascade Microtech MPS150, an automated channel was developed for testing memristor structures, in the mode of multiple reading and writing. VI "RW MIM" forms a sequence of pulses of the specified amplitude and duration in the write / read modes at the SMU output of the source. The deposition and validation of 5,11-dimethyl-5,11-dihydroindolo [3.2-b] carbazole and 5,11-dihexyl-5,11-dihydroindolo [3.2-b] carbazole films was performed. From the measured volt-ampere characteristics, it was found that the semiconductor in the synthesized TiN / DMICZ / Au, Ti / DMICZ / Au structures has a hole conductivity with a mobility μ = 4.9 ∙ 10-7 cm2/(V∙s). It is shown that the recorded I-V characteristic is characterized by hysteresis loops that indicate the presence of a memorial effect in TiN / DHICZ / Au samples. The testing of layered structures under test in multiple read / write modes was performed.

Спроектирована установка для нанесения органических покрытий. Установка термовакуумного нанесения и виртуальный прибор «ThermoVAC&Co» позволяют осуществлять синтез тонкопленочных покрытий, контролируя температуру нагрева испаряемого вещества до 500 °C. Выполнен синтез тонких пленок 5,11-диметил-5,11-дигидроиндоло [3.2-b]карбазола 5,11-дигексил-5,11-дигидроиндоло[3.2-b]карбазола, 5,11-бис(2-метоксиэтил)-5,11-дигидроиндоло[3,2-b]карбазола и 5,11-бис[2-(2-метоксиэтокси)этокси]-5,11-дигидроиндоло[3,2-b]карбазола для исследования оптических и электрических характеристик. С помощью конфокального микроскопа Axio CSM 700 была проведена аттестация поверхности синтезируемых покрытий. Спектры оптического поглощения были получены на спектрометре Shimadzu UV-2450. Расчетный потенциал ионизации для исследованных соединений ICZ составляет 6,82-7,1 эВ. Обсуждается влияние отдельных блоков соединений на спектр оптического поглощения. На базе микрозондовой станции Cascade Microtech MPS150 произведены измерения вольтамперных характеристик структуры ITO/-ICZ/Al. По данным ВАХ были рассчитаны подвижности зарядов по модели инжекционных токов. Подвижность носителей заряда, оцененная по вольтамперным характеристикам, находится в диапазоне 2,2 ∙ 10-9–1,43 ∙ 10-6 см2 / (В·сек) для исследованных соединений ICZ. Установлена связь между интенсивностью полос поглощения с максимумом около 430 нм и подвижностью носителей заряда. / The installation for applying organic coatings is designed. The thermal vacuum deposition unit and the «ThermoVAC & Co» virtual instrument allow the synthesis of thin-film coatings, controlling the temperature of heating the evaporated substance up to 500 ° C. The thin films of 5,11-dimethyl-5,11-dihydroindolo [3.2-b] carbazole 5,11-dihexyl-5,11-dihydroindolo [3.2-b] carbazole, 5,11-bis (2-methoxyethyl) - 5,11-dihydroindolo [3,2-b] carbazole and 5,11-bis [2- (2-methoxyethoxy) ethoxy] -5,11-dihydroindolo [3,2-b] carbazole were synthesized to study optical and electrical characteristics. The surface of the synthesized coatings was certified using the Axio CSM 700 confocal microscope. Optical absorption spectra were obtained with the Shimadzu UV-2450 spectrometer. The calculated ionization potential is 6.82–7.1 eV for the studied ICZ compounds. The effect of individual blocks of compounds on the optical absorption spectrum is discussed. The current-voltage characteristics of the ITO / -ICZ / Al structure were measured with the Cascade Microtech MPS150 microprobe station. According to the I-V characteristics data, the charge mobility was calculated using the injection current model. The mobility of charge carriers, estimated by the current-voltage characteristics, is in the range 2,2 ∙ 10-9–1,43 ∙ 10-6 cm2/ (V·sec) for the studied ICZ compounds. The relationship between the intensity of absorption bands with a maximum near 430 nm, and the mobility of charge carriers were found.

No / OBJECTIVES: To compare the properties of solid dispersions of felodipine for oral bioavailability enhancement using two different polymers, polyvinylpyrrolidone (PVP) and hydroxypropyl methylcellulose acetate succinate (HPMCAS), by hot-melt extrusion (HME) and spray drying. METHODS: Felodipine solid dispersions were prepared by HME and spray drying techniques. PVP and HPMCAS were used as polymer matrices at different drug : polymer ratios (1 : 1, 1 : 2 and 1 : 3). Detailed characterization was performed using differential scanning calorimetry, powder X-ray diffractometry, scanning electron microscopy and in-vitro dissolution testing. Dissolution profiles were evaluated in the presence of sodium dodecyl sulphate. Stability of different solid dispersions was studied under accelerated conditions (40 degrees C/75% RH) over 8 weeks. KEY FINDINGS: Spray-dried formulations were found to release felodipine faster than melt extruded formulations for both polymer matrices. Solid dispersions containing HMPCAS exhibited higher drug release rates and better wettability than those produced with a PVP matrix. No significant differences in stability were observed except with HPMCAS at a 1 : 1 ratio, where crystallization was detected in spray-dried formulations. CONCLUSIONS: Solid dispersions of felodipine produced by spray drying exhibited more rapid drug release than corresponding melt extruded formulations, although in some cases improved stability was observed for melt extruded formulations.

No / The current work was undertaken to assess suitability of liquid crystalline phase for engineering of lactose crystals and their utility as a carrier in dry powder inhalation formulations. Saturated lactose solution was poured in molten glyceryl monooleate which subsequently transformed into gel. The gel microstructure was analyzed by PPL microscopy and SAXS. Lactose particles recovered from gels after 48 h were analyzed for polymorphism using techniques such as FTIR, XRD, DSC and TGA. Particle size, morphology and aerosolisation properties of prepared lactose were analyzed using Anderson cascade impactor. In situ seeding followed by growth of lactose crystals took place in gels with cubic microstructure as revealed by PPL microscopy and SAXS. Elongated (size approximately 71 mum) lactose particles with smooth surface containing mixture of alpha and beta-lactose was recovered from gel, however percentage of alpha-lactose was more as compared to beta-lactose. The aerosolisation parameters such as RD, ED, %FPF and % recovery of lactose recovered from gel (LPL) were found to be comparable to Respitose(R) ML001. Thus LC phase (cubic) can be used for engineering of lactose crystals so as to obtain particles with smooth surface, high elongation ratio and further they can be used as carrier in DPI formulations.

[ES] La presente tesis doctoral aborda el almacenamiento y producción de hidrógeno verde en compuestos químicos, tales como el metanol, ácido fórmico o en heterociclos aromáticos nitrogenados, mediante el desarrollo de (foto)catalizadores que sean eficientes para la formación de estos compuestos orgánicos líquidos por hidrogenación selectiva del CO2 o para la liberación de hidrógeno. Ambos tipos de procesos son necesarios para la implementación del H2 verde como vector energético sin huella de carbono. De esta manera el objetivo común a todos los capítulos de la presente Tesis es el desarrollo (foto)catalizadores innovadores que exhiban una mayor actividad y selectividad en estos procesos respecto al estado del arte y que operen en condiciones más convenientes. Específicamente las reacciones estudiadas han sido la hidrogenación selectiva de CO2 a metanol, ciclos de hidrogenación/deshidrogenación del N-etilcarbazol y de sus derivados parcial o totalmente hidrogenados, el reformado en fase acuosa del metanol y la fotodescarboxilación del ácido fórmico. La tesis describe la preparación, estudio de actividad y estabilidad, la determinación de los centros activos y cálculos sobre los mecanismos de reacción para estos procesos. Mediante una estructura de introducción, discusión de resultados y conclusión desde el capítulo III al capítulo VII se describe de manera exhaustiva y mediante una discusión amplica los procesos (foto) catalíticos (ensayos catalíticos, estudios de mecanismo de reacción, descripción de (foto)catalizadores) llevados a cabo para lograr los objetivos. Los detalles experimentales, la síntesis de los materiales y los procedimientos de reacción se indican en el capítulo VIII de la Tesis. Finalmente el capítulo IX resume las conclusiones a las que se ha llegado en el presente estudio y que representa un avance sustancial respecto al estado del arte. / [CA] La present tesi doctoral aborda l'emmagatzematge i producció d'hidrogen verd en compostos químics, com ara el metanol, àcid fòrmic o en heterocicles aromàtics nitrogenats, mitjançant el desenvolupament de (foto)catalitzadors que siguen eficients per a la formació d'aquests compostos orgànics líquids per hidrogenació selectiva del CO2 o per a l'alliberament d'hidrogen. Ambdós tipus de processos són necessaris per a la implementació de l'H2 verd com a vector energètic sense petjada de carboni. D'aquesta manera, l'objectiu comú a tots els capítols de la present tesi és el desenvolupament de (foto)catalitzadors innovadors que exhibisquen una major activitat i selectivitat en aquests processos respecte a l'estat de l'art i que operen en condicions més convenients. Específicament, les reaccions estudiades han sigut la hidrogenació selectiva de CO2 a metanol, cicles d'hidrogenació/deshidrogenació del N-etilcarbazol i dels seus derivats parcialment o totalment hidrogenats, la reformació en fase aquosa del metanol i la fotodescarboxilació de l'àcid fòrmic. La tesi descriu la preparació, estudi d'activitat i estabilitat, la determinació dels centres actius i càlculs sobre els mecanismes de reacció per a aquests processos. Mitjançant una estructura d'introducció, discussió de resultats i conclusió des del capítol III fins al capítol VII es descriu de manera exhaustiva i mitjançant una discussió àmplia els processos (foto)catalítics (assaigs catalítics, estudis de mecanisme de reacció, descripció de (foto)catalitzadors) realitzats per a aconseguir els objectius. Els detalls experimentals, la síntesi dels materials i els procediments de reacció s'indiquen en el capítol VIII de la tesi. Finalment, el capítol IX resumeix les conclusions a les quals s'ha arribat en el present estudi i que representa un avanç substancial respecte a l'estat de l'art. / [EN] This doctoral thesis addresses the storage and production of green hydrogen in chemical compounds such as methanol, formic acid, or nitrogenous aromatic heterocycles, through the development of (photo)catalysts that are efficient for the formation of these liquid organic compounds by selective hydrogenation of CO2 or for the release of hydrogen. Both types of processes are necessary for the implementation of green H2 as a carbon-free energy vector. Thus, the common objective of all chapters in this thesis is the development of innovative (photo)catalysts that exhibit greater activity and selectivity in these processes compared to the state of the art and that operate under more convenient conditions. Specifically, the reactions studied were the selective hydrogenation of CO2 to methanol, hydrogenation/dehydrogenation cycles of N-ethylcarbazole and its partially or fully hydrogenated derivatives, aqueous phase reforming of methanol, and photodecarboxylation of formic acid. The thesis describes the preparation, activity and stability studies, determination of active sites, and calculations on the reaction mechanisms for these processes. Through a structure of introduction, discussion of results, and conclusion from Chapter III to Chapter VII, the (photo)catalytic processes (catalytic tests, reaction mechanism studies, description of (photo)catalysts) carried out to achieve the objectives are exhaustively described and thoroughly discussed. The experimental details, synthesis of materials, and reaction procedures are indicated in Chapter VIII of the thesis. Finally, Chapter IX summarizes the conclusions reached in the present study, which represents a substantial advance over the state of the art / García Baldoví, A. (2024). Catálisis para el almacenamiento y generación de hidrógeno [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/208436

Das fundamentale Verständnis von Ladungsträgern in molekularen Halbleitern, die typischerweise als Polaronen bezeichnet werden, ist unverzichtbar, wenn es um das Design besonders leistungsfähiger (opto)elektronischer Bauelemente geht. Die vorliegende Arbeit hat zum Ziel ein umfangreiches Bild der Energetik von Polaronen in organischen Halbleitern zu erhalten. Zunächst geht es darum einen Probenaufbau zu finden, der es nicht nur ermöglicht Ladungsträger zu generieren, sondern auch ihre elektronische Struktur unter Verwendung von komplementären Photoemissionstechniken – Rötngen-, Ultraviolett- und inverse Photoelektronenspektroskopie - aufzuklären. Das Probenkonzept basiert darauf, dass molekulare Filme, die eine niedrigere Ionisierungsenergie als die Austrittsarbeit des zugrunde liegenden Substrates aufweisen, Fermi-level Pinning zeigen. In diesem Fall wären die höchsten besetzten Zustände der neutralen molekularen Schicht energetisch oberhalb des Substrat-Fermi-Levels angeordnet, wodurch zum Erhalt des elektronischen Gleichgewichts die Notwendigkeit für einen Ladungstransfer gegeben ist. Da die starke elektronische Kopplung zwischen Molekülen und Metallen die spektrale Information der Überschussladungsträger verändern könnte, wird die Metalloberfläche durch eine ultradünne Zwischenschicht passiviert. Die Ergebnisse zeigen, dass es durch die vorliegende starke on-site Coulomb Repulsion zur Aufspaltung des höchsten besetzen molekularen Niveaus in ein besetztes und ein unbesetztes Sub-niveau kommt. Dies widerspricht der seit Jahren etablierten Vorstellung von einem einfach besetzten Niveau in der Bandlücke des neutralen molekularen Halbleiters. Unter zusätzlicher Berücksichtigung der inter-site Coulomb Repulsion zwischen Molekülionen und neutralen Molekülen, sowie der Energieniveau Verbiegung kann schließlich ein vollständiges Bild entwickelt werden, das die etablierte Vorstellung der Energieniveaus von Ladungsträgern in molekularen Halbleitern ersetzen soll. / Understanding the nature of charge carriers in molecular semiconductors, typically termed "polarons", is indispensable for rational material design targeting future superior (opto-)electronic device performance. The present work addresses this fundamental issue to derive a comprehensive picture of polarons in organic semiconductors. Conceptual work is dedicated to identifying a sample structure, which allows both, deliberately generating charged molecules and applying the complementary photoemission techniques X-ray, ultraviolet and inverse photoelectron spectroscopy in order to assess the polaron energetics. The sample concept is based on the fact that molecular layers exhibiting an ionization energy lower than the work function of the supporting substrate show Fermi-level pinning. There, as the substrate Fermi-level is moved into the occupied density of states of the molecular adsorbate, electron transfer occurs from the molecules to the substrate. Because strong electron coupling between molecules and eg. metal surfaces might mask or alter the spectral information of excess charge carriers, such interaction needs to be inhibited by implementation of an ultrathin passivating interlayer. The comprehensive results provide evidence that the highest occupied molecular orbital level is split into an upper unoccupied and a lower occupied sub-level due to strong on-site Coulomb interaction. This finding is in marked contrast to what has been assumed for decades, where a singly occupied level was proposed to lie within the gap of the neutral molecular semiconductor. Moreover, taking into account the inter-site Coulomb interaction between molecular cations and surrounding neutral molecules, as well as energy-level bending, finally, a complete picture of the energetics associated with polarons in molecular semiconductors could be derived, which aims at replacing common perceptions.

This study attempted to establish the travel behaviours and choice criteria of the South African domestic air passenger and how they differed between low-cost carriers (LCCs) and full-service carriers (FSCs). The study was quantitative and used structured questionnaires to collect data via personal interviews. Descriptive and inferential techniques were used to analyse the data, including a binomial logistic regression to identify predictors of model choice. Analysis This study attempted to establish the travel behaviours and choice criteria of the South African domestic air passenger and how they differed between low-cost carriers (LCCs) and full-service carriers (FSCs). The study was quantitative and used structured questionnaires to collect data via personal interviews. Descriptive and inferential techniques were used to analyse the data, including a binomial logistic regression to identify predictors of model choice. Analysis showed that passengers had a limited understanding of the functioning of the models. This results in consumer perceptions and expectations being discordant with the true differences. In distinguishing between models, LCC passengers rate LCCs more favourably than FSC passengers, but both rate FSCs higher than LCCs. This shows the need of consumers to have the features and services of the FSCs. Amongst the key findings was the absolute importance of price to the passengers on both models when purchasing the ticket. The analysis showed that LCC passengers are highly price sensitive and show loyalty to the lowest price (not airline model). It was apparent that frequent flyer programmes (FFP), or linkages to 3rd party loyalty programmes, for LCCs need to be reconsidered. Younger LCC passengers especially, indicated a need for a simple FFP to receive some form of ‘reward’, as well as benefits traditionally only offered by FSCs. FSC passengers show a greater degree of loyalty and less fare sensitivity. This provides the FSCs with a degree of fare flexibility and the opportunity to move their loyal, less price-sensitive consumers up the price curve to maximise revenue. It was shown that, in distinguishing themselves from FSCs, it is important that LCCs are perceived as being more affordable than FSCs and are offering a value-for-money service. In essence, LCCs have to defend their positioning by (i) ensuring that their fares are not perceived to be as high as a FSCs and (ii) watching that the FSC fares are not declining to a level where FSCs are perceived as being as cheap as a LCC. For LCCs, brand building strategies around issues other than fare need to be devised, with attention paid to identifying determinant factors. / Business Management / D. Com (Business Management)