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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
41

Image Processing Algorithms for Realizing a Seamless Multi-Projection Screen

Ye, Xiuxian Jr January 2020 (has links)
This is a kind of image processing algorithm in order to realize a seamless video wall and improve the quality of images. / Nowadays, screens are very common in our daily life. There are several di erent kinds of screens, LCD, LED, OLED, ULED and so on. LCD screens can display high-resolution pictures while LED has advantages of low energy consumption and wider color range. This project has two goals. The rst one is to achieve a seamless display screen which consists of 9 LED backlit LCD boards. The second goal is to improve image quality, which is enabled by the combination of LED and LCD. There are two main problems that need to be solved in this project. The rst problem is brightness correction. Because of the projection method and the distance between lights and nal screen, there are di erent kinds of overlapping situations and distinct lines on screen. The other one is the combination of LED and LCD. The algorithms need to be developed to ensure that RGB LEDs and LCD panels display the same picture and to address some problems caused by the LCD module. / Thesis / Master of Applied Science (MASc)
42

A Test of the Penman Combination Model for Potential Evapotranspiration

McCaughey, John H. 05 1900 (has links)
<p> The Penman combination model for potential evapotranspiration, using the improved wind function of Businger (1956), and measured net radiation, was tested for daily and hourly totals, over an irrigated perennial ryegrass surface at Simcoe, Norfolk County, Southern Ontario. The standard measurement of evapotranspiration was the energy balance method, using the Bowen ratio. The component fluxes of the energy balance were evaluated for ninety-seven hours on ten separate days. A comparison is made of two days with markedly different moisture availability to show how the magnitude of the component fluxes changed. Also the effect of the plant on the evaporative flux is examined. On days when water was non-limiting the model gave excellent results for hourly and daily totals: within 5% of measured evapotranspiration. When water became limiting the model overestimated by as much as 30%. It is further shown that the Penman model appears to be more sensitive to changes in the evaporative flux than the water equivalent of net radiation, The relationship of cumulative dry matter production of the crop and cumulative potential evapotranspiration was examined and was found to be linear for most of the field season, substantiating the hypothesis of Penman (1962).</p> / Thesis / Master of Arts (MA)
43

The Combination of Microbore Liquid Chromatography and Mass Spectrometry

Gergely, Robert John 03 1900 (has links)
<p> An inexpensive method was developed for the conversion of a high performance liquid chromatography (HPLC) system for use with 1 mm I.D. microbore columns. Chromatographic performance of the system was tested under both isocratic and gradient elution conditions, using a standard mixture of 16 polycyclic aromatic hydrocarbons (PAH).</p> <p> The microbore column HPLC was also coupled to a mass spectrometer equipped with a moving belt interface. Chromatographic performance under isocratic and gradient elution and mass spectral performance under scanning and selected ion monitoring modes were tested using the PAH standard.</p> <p> A marine sediment extract was subjected to qualitative and quantitative analysis for PAH. Qualitative results on the sample were obtained from a combination of retention indices, mass spectra, and retention times. Quantitation was performed by microbore column liquid chromatography-mass spectrometry (LC/MS) in the selected ion monitoring mode of operation. The method of calibration used was external calibration.</p> <p> The microbore column HPLC system exhibited good chromatographic behavior. Resolution, peak shape and short term retention time reproducibility were good, although, long term retention time fluctuations, due to changing mobile phase flow rates, were noted.</p> <p> The combination of microbore column HPLC with a moving belt interface and mass spectrometer gave excellent results. Problems commonly encountered with conventional column (4.6 mm I.D.) LC/MS, such as backstreaming, droplet formation, and splattering were greatly reduced, resulting in no apparent loss of chromatographic integrity and stable mass spectrometer operating conditions. These operating conditions proved to be most advantageous in the quantitative analysis of the marine sediment extract by selected ion monitoring.</p> / Thesis / Master of Science (MSc)
44

Anticancer Activities of Resveratrol Alone and in Combination with Ascorbic Acid

Zhang, Huiying 22 April 2010 (has links)
No description available.
45

Colourful Feasibility: Algorithms, Bounds and Implications

Huang, Sui 07 1900 (has links)
<p> Given a point p and d + 1 sets (i.e., colours) of points in dimension d, the Colourful Feasibility Problem is to decide whether there are d + 1 points of different colours containing p in their convex hull; and if yes, find such a point set. The monochrome version of this problem, expressing p as a linear combination of d + 1 points in a set S, can be solved using traditional linear optimization algorithms. The Colourful Feasibility Problem was presented by Bárány and Onn in 1997, and it is still not known if a polynomial-time algorithm exists. The case where we have d colours in dimension d and no restriction on the size of the sets has been shown to be strongly NP-complete through a reduction of 3-SAT. We define the core of a configuration to be the intersection of the convex hulls of each colour. We start from the important subcase that we call Colourful Core Feasibility Problem where we have d + 1 points of each colour, and p in the core. By Bárány's 1982 Colourful Caratheodory Theorem, a solution is guaranteed to exist, and the problem is to exhibit one. This problem is described by Bárány and Onn as "an outstanding problem on the border line between tractable and intractable problems". Besides applications to combinatorics, The Colourful Feasibility Problem models a situation where we want to select a set of points that is both diverse and representative.</p> <p> While we have not found out whether the Colourful Core Feasibility Problem can be solved in polynomial time, our contributions are on both the theoretical and practical performance of algorithms to solve the Colourful Feasibility Problem. The algorithms proposed by Bárány and Onn are essentially geometric, and the complexity guarantees depend crucially on having p inside the core. We consider modifications of these algorithms which update multiple colours at each stage, as well a greedy heuristic where we choose the adjacent simplex of maximum volume in each iteration and a random sampling approach. Our test suite includes unstructured random problems, ill-conditioned problems, problems with a restricted number of solutions and infeasible problems. We conclude that the most robust and nearly fastest algorithm for the Colourful Core Feasibility Problem is the multi-update variant which yields substantial gains over the original ones. Alternative approaches based on nondefinite quadratic optimization problem and positive semidefinite relaxation, and a combinatorial algorithm not depending on having p in the core are also introduced. Finally, we give the first upper bound for the minimal number of colourful simplices containing a core point and the first improvement of the lower bound since Bárány's result in 1982.</p> / Thesis / Master of Science (MSc)
46

Effect of Ultrasound on Molecular Structure Development of Polylactide

Bao, W., Wu, H., Guo, S., Paradkar, Anant R, Kelly, Adrian L., Brown, Elaine, Coates, Philip D. January 2014 (has links)
Yes / In this work, effect of ultrasound on molecular structure development of Polylactide (PLA) was studied. It was found that the intrinsic viscosity of PLA decreased with increasing treating time, temperature and ultrasound time. Different from traditional thermal degradation of PLA, the degradation of PLA under ultrasound treatment showed that chain scission and chain combination of PLA competed with each other in the degradation process, which could be divided into two steps. The mechanism of ultrasound degradation of PLA was proposed. Furthermore, Thermal properties were characterized by DSC to show heat and ultrasound effects on molecular structure development of PLA.
47

CONFORMATIONALLY SWITCHABLE POLYGLUTAMATES AS A PROSPECTIVE MATERIAL FOR POLYMER THERAPEUTICS DESIGN

Zagorodko, Oleksandr 12 June 2020 (has links)
[ES] Los tratamientos en los que se utilizan Polímeros Terapéuticos ofrecen numerosas ventajas en comparación con los tratamientos convencionales y otros enfoques de nanomedicina. Entre estas ventajas se puede destacar la especificidad para cruzar ciertas barreras biológicas y su capacidad de acumulación pasiva en tumores. Además, la conjugación de fármacos a polímeros ofrece ventajas adicionales tales como una farmacocinética mejorada, multivalencia, co-entrega de fármacos en la proporción deseada y liberación/activación específica en el sitio de acción requerido a través de la aplicación de enlaces polímero-fármaco que responden a estímulos fisiológicos. Uno de los tipos más importantes de polímeros que se utiliza para la administración de fármacos pertenecen a los polielectrolitos polipeptídicos. Su uso se debe principalmente, a su biocompatibilidad, biodegradabilidad, multivalencia y versatilidad estructural, así como a la plasticidad sintética en la modificación de cadenas laterales. La aplicación conjunta de ciencia de polielectrolitos con otras ramas de la química es muy prometedora; sin embargo, aún permanece en un estadío temparano en su desarrollo. Esto es debido a que, el control del autoensamblaje de polielectrolitos sigue siendo una tarea complicada y la investigación en esta área puede resultar muy laboriosa a la hora de encontrar sistemas biocompatibles más avanzados con un único perfil de acción y por supuesto, se abre un nuevo campo de estudio sobre las nuevas propiedades desconocidas de estos. Este tema es novedoso por la posibilidad de realizar diferentes estudios de combinación de polielectrolitos con residuos supramoleculares y representa el estudio de nuevas arquitecturas potencialmente mas complicadas. En la presente tesis doctoral se estudiarán el desarrollo de sistemas de administración de fármacos basados en polielectrolitos supramoleculares con un alto grado de control sobre las propiedades fisicoquímicas, centrándose principalmente en el control de la forma y el tamaño. Se han estudiado en profundidad varias familias de poliglutamatos de forma estrella con núcleos de diferente hidrofobicidad para determinar cómo la estructura del núcleo y la longitud de la cadena de polielectrolitos afectan el mecanismo de autoensamblaje. Una vez que se definieron estas correlaciones, se seleccionaron los candidatos más prometedores para la preparación de dos sistemas de transportede fármacos que consisten en partículas esféricas o en forma de cilindro. Finalmente, también se realizó la conjugación de varios fármacos (fasudil y dinaciclib) como agentes únicos o en combinación a través de diferentes enlaces biodegradables. Las propiedades fisicoquímicas y la actividad in vitro de los conjugados se estudiaron en profundidad y actualmente se están llevando a cabo experimentos in vivo en un modelo de cáncer de mama metastásico triple negativo ortotópico preclínicamente relevante, con los conjugados previamente seleccionados. / [CA] Els tractaments en els quals s'utilitzen Polímers Terapèutics ofereixen nombrosos avantatges en comparació amb els tractaments convencionals i altres enfocaments amb nanomedicina. Entre aquests avantatges es pot destacar l'especificitat per creuar certes barreres biològiques i la seva capacitat d'acumulació passiva en tumors. A més, la conjugació de fàrmacs a polímers ofereix avantatges addicionals com ara una farmacocinètica millorada, multivalència, co-lliurament de fàrmacs en la proporció desitjada i alliberament / activació específica en el lloc d'acció requerit a través de l'aplicació d'enllaços polímer-fàrmac que responen a estímuls fisiològics. Un dels tipus més importants de polímers que s'utilitza per a l'administració de fàrmacs pertanyen als polielectròlits polipeptídics. El seu ús es deu principalment, ala seua biocompatibilitat, biodegradabilitat, multivalència i versatilitat estructural, així com a la plasticitat sintètica en la modificació de cadenes laterals. L'aplicació conjunta de ciència de polielectròlits amb altres branques de la química és molt prometedora; però, encara roman en un estadi primerenc en el seu desenvolupament. Això és degut al fet que, el control de l'autoensamblatge de polielectròlits segueix sent una tasca complicada i la investigació en aquesta àrea pot resultar molt laboriosa a l'hora de trobar sistemes biocompatibles més avançats amb un únic perfil d'acció i per descomptat, s'obre un nou camp d'estudi sobre les noves propietats desconegudes d'aquests. Aquest tema és nou j que ofereix la possibilitat de realitzar diferents estudis de combinació de polielectròlits amb residus supramoleculars i representa l'estudi de noves arquitectures potencialment més complicades. En la present tesi doctoral s'estudiaran el desenvolupament de sistemes d'administració de fàrmacs basats en polielectròlits supramoleculars amb un alt grau de control sobre les propietats fisicoquímiques, centrant-se principalment en el control de la forma i la mida. S'han estudiat en profunditat diverses famílies de poliglutamatos de forma estrella amb nuclis de diferent hidrofobicitat per determinar com l'estructura delnucli i la longitud de la cadena de polielectròlits afecten el mecanisme de autoensamblatge. Una vegada que es van definir aquestes correlacions, es van seleccionar els candidats més prometedors per a la preparació de dos sistemes de transport de fàrmacs que consisteixen en partícules esfèriques o en forma de cilindre. Finalment, també es va realitzar la conjugació de diversos fàrmacs (fasudil i dinaciclib) com a agents únics o en combinació a través de diferents enllaços biodegradables. Les propietats fisicoquímiques i l'activitat in vitro dels conjugats es van estudiar en profunditat i actualment s'estan duent a terme experiments in vivo en un model ortotòpic de càncer de mama metastàtic triple negatiu preclínicament rellevant, amb els conjugats prèviament seleccionats. / [EN] Treatments based on polymer therapeutics offer numerous advantages when compared to conventional treatments and other nanomedicine approaches. These include passive tumor accumulation and the ability to cross specific biological barriers. Furthermore, polymer conjugation of drugs offers additional advantages such as improved pharmacokinetics, multivalency, co-delivery of drugs at the desired ratio, and specific release/activation at the required site of action via the application of polymer-drug linkers that respond to physiological stimuli. One of the most important types of polymers suitable for drug delivery belong to polypeptide polyelectrolytes, mainly due to their biocompatibility and synthetic plasticity of side chain modification. The merging of polyelectrolyte science with other branches of chemistry seems very promising; however, it still remains in an embryonic state. While the control of polyelectrolyte self-assembly remains a complicated task, research in this area may provide more advanced biocompatible systems with unique profiles of action and new materials with yet unknown properties. The combination of polyelectrolytes with supramolecular moieties represents an especially interesting research topic, with the potential to derived more complicated architectures. This thesis is focused on the development of supramolecular-polyelectrolyte-based drug delivery systems with high degree of control over physicochemical properties, focusing mainly on shape and size. Several families of star-polyglutamates with cores of different hydrophobicity have been studied in depth in order to determine how the core structure and polyelectrolyte chain length affect self-assembly mechanism. Once these correlations were defined, the most promising candidates were selected for preparation of two drug delivery systems consisting of either spherical or rod-like particles. Finally, conjugation of several drugs (fasudil and dinaciclib) as single agents or in combination through different responsive linkers were also performed; physicochemical properties and in vitro activity of the conjugates were studied in depth and in vivo experiments with selected conjugates are currently ongoing in a preclinically relevant orthotopic Triple Negative Metastatic Breast Cancer Model. / Zagorodko, O. (2020). CONFORMATIONALLY SWITCHABLE POLYGLUTAMATES AS A PROSPECTIVE MATERIAL FOR POLYMER THERAPEUTICS DESIGN [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/146228
48

The antimicrobial interactions of Agathosma crenulata, Dodonaea viscosa and Eucalyptus globulus combination and their chemical profiling

Zonyane, Samkele 12 1900 (has links)
Thesis (MSc)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: In traditional medicine, there is a long-standing culture of combining herbal drugs to increase the therapeutic efficacy. The improved medical action is thought to be due to synergistic interactions between different plant bioactive components. The aim of this study was to test the pharmacological interactions in a medicinal plant combination which consisted of Agathosma crenulata, Dodonaea viscosa and Eucalyptus globulus. The rationale for the analysis of this particular mixture is that it had noteworthy antibacterial activity and exhibited the highest activity out of seven medicinal plant mixtures previously investigated. Using chromatographic analysis, the phytochemistry of the plants was also assessed. The chloroform: methanol (1:1; v/v) extracts or hydo-distilled essential oils (A. crenulata and E. globulus) were screened individually and in combinations (double and triple plant combination) for activity against five respiratory pathogens using a microdilution assay. The antimicrobial interactions in combinations were assessed with the fractional inhibitory concentration (FIC) and the isobolograms. The organic extracts generally showed the highest antimicrobial activity with E. globulus having the highest activity with MIC values below 1 mg ml-1 representing noteworthy activity. The overall activity of the aqueous extracts was poor. The essential oil activity of E. globulus was mostly noteworthy (0.5 to 2 mg ml-1) while A. crenulata essential oil displayed moderate activity (1 to 4 mg ml-1). The ΣFIC values for double combinations (1:1) of A. crenulata with D. viscosa, A. crenulata with E. globulus and D. viscosa with E. globulus were calculated from the minimum inhibitory concentration (MIC) data and the interactions were classified as synergistic, additive, indifferent and antagonistic. The highest synergistic interactions observed were for a 1:1 combination of A. crenulata with E. globulus against K. pneumoniae, S. aureus and B. subtilis with ΣFIC values of 0.07. There was only one incident of antagonism noted in the study for D. viscosa with E. globulus (1:1) against C. neoformans with ΣFIC value of 4.25. The double combinations against selective pathogens (K. pneumoniae, S. aureus and E. coli) were further analysed for interactions using isobolograms. Mostly, the antimicrobial interactions as presented by the isobolograms were congruent with FIC results which further validated the occurrence of relevant antimicrobial interactions in those combinations. The ΣFIC values for triple combinations (1:1:1) revealed mostly synergistic interactions. When the triple combinations were analysed further against certain pathogens based on the predictions of the Design of Experiments software program (MODDE 9.1®), the MIC values remained the same despite the different combinations that were tested Thin layer chromatography (TLC) was used for a quick chemical fingerprinting of the plant extracts. This was followed by a bio-autographic assay. The chemical profiles of the organic extracts and essential oils from two of the study aromatic plants (A. crenulata and E. globulus) were further analysed with liquid chromatography mass spectrometry (LC-MS) and gas chromatography mass spectrometry (GC-MS) respectively. For combined plant extracts, a multivariate data analysis using principal component analysis (PCA) and hierarchical clustering analysis (HCA) was used to determine the relationship of the chemical make-up of combinations with that of individual plant extracts. According to the TLC analysis, E. globulus extracts had more compounds than the other two plants in the study. For the bio-autographic assay, E. globulus and combinations that included this plant showed greater inhibition zones than A. crenulata and D. viscosa. For the LC-MS analysis, PCA and HCA showed a close relationship between A. crenulata with D. viscosa, D. viscosa with E. globulus and the triple combination. Twenty one components were identified in the essential oil of A. crenulata representing 88.83% of the total oil composition. The oil was dominated by oxygen-containing monoterpenes (46.25%). In the essential oil of E. globulus, twenty six compounds were identified making up to 95.62% of the oil composition. Oxygen-containing monoterpenes (32.98%) also dominated the E. globulus essential oil. There was no great variation in essential oil metabolites of the individual plants and their combination as shown by both PCA and HCA. The enhanced in vitro antimicrobial activity and pharmacological interactions (synergy and additivity) in some of the combinations (double and triple) that were tested in this study adds scientific support to the use of medicinal plant combinations in Western Cape traditional medicine. The metabolic profiles of plants in combination might be unique due to interaction of the different plant bioactive molecules and thus result into defined antimicrobial activity. / AFRIKAANSE OPSOMMING: In tradisionele geneeskunde is dit ’n lank bestaande kultuur om kruiemiddels te kombineer om die terapeutiese werking daarvan te verhoog. Dié verbeterde mediese werking word toegeskryf aan die oënskynlik sinergistiese interaksies tussen verskillende bioaktiewe plantkomponente. Die doel van hierdie studie was om die farmakologiese interaksies in medisinale plantkombinasies van Agathosma crenulata, Dodonaea viscosa en Eucalyptus globulus te bestudeer. Daar is op die ontleding van hierdie spesifieke mengsel besluit omdat dit oor beduidende antibakteriese waarde beskik en omdat dit uit sewe medisinale plantmengsels wat voorheen bestudeer is, as die doeltreffendste een aangewys is. Die fitochemie van die plante is ook met behulp van chromatografiese ontleding beoordeel. Deur middel van ’n mikroverdunningstoets is die chloroform:metanol- (1:1; v/v-)ekstrakte of hidrogedistilleerde vlugtige olies (A. crenulata en E. globulus) individueel sowel as in kombinasie (dubbele en drievoudige plantkombinasies) nagegaan vir hul werking met betrekking tot vyf respiratoriese patogene. Die gekombineerde antimikrobiese interaksies is met behulp van fraksioneel stremmende konsentrasie (FIC) en isobologramme ondersoek. Die organiese ekstrakte het oor die algemeen die meeste antimikrobiese aktiwiteit by E. globulus getoon, met MIC-waardes onder 1 mg ml-1 wat as noemenswaardige aktiwiteit beskou is. Die algehele aktiwiteit van die waterekstrakte was swak. Die vlugtige-olieaktiwiteit van E. globulus was merendeels noemenswaardig (0,5 tot 2 mg ml-1), terwyl die vlugtige olie van A. crenulata matige aktiwiteit getoon het (1 tot 4 mg ml-1). Die ΣFIC-waardes vir dubbelkombinasies (1:1) van A. crenulata en D. viscosa, A. crenulata en E. globulus, en D. viscosa en E. globulus is uit die minimum stremmende konsentrasie (MIC) bereken en die interaksies is as sinergisties, additief, neutraal en antagonisties geklassifiseer. Die sterkste sinergistiese interaksies is by ’n 1:1-kombinasie van A. crenulata en E. globulus met betrekking tot K. pneumoniae, S. aureus en B. subtilis opgemerk, met ΣFIC-waardes van 0,07. Die studie het slegs een geval van antagonisme opgelewer, naamlik by D. viscosa en E. globulus (1:1) met betrekking tot C. neoformans, wat ’n ΣFIC-waarde van 4,25 geregistreer het. Die werking van die dubbelkombinasies met betrekking tot gekose patogene (K. pneumoniae, S. aureus en E. coli) is voorts met behulp van isobologramme vir interaksies nagegaan. Die antimikrobiese interaksies wat uit die isobologramme geblyk het, was meestal in pas met FIC-resultate, wat die bestaan van tersaaklike antimikrobiese interaksies in daardie kombinasies verder bevestig het. Die ΣFIC-waardes vir die drievoudige kombinasies (1:1:1) het meestal sinergistiese interaksies aan die lig gebring. Toe die drievoudige kombinasies verder op grond van die voorspellings van die sagteware Design of Experiments (MODDE 9.1®) met betrekking tot sekere patogene ontleed is, het die MIC-waardes onveranderd gebly, ondanks verskillende toetskombinasies. Dunlaagchromatografie (TLC) is vir ’n vinnige chemiese ontleding van die plantekstrakte gebruik en is gevolg deur ’n bio-outografiese toets. Die chemiese profiele van die organiese ekstrakte en vlugtige olies van twee van die aromatiese plante in die studie (A. crenulata en E. globulus) is verder met vloeistofchromatografie-massaspektrometrie (LC-MS) en gaschromatografie-massaspektrometrie (GC-MS) onderskeidelik ontleed. Vir gekombineerde plantekstrakte is veelveranderlike-ontleding in die vorm van hoofkomponentontleding (PCA) en hiërargiese groepsontleding (HCA) gebruik om die verhouding van die chemiese samestelling van kombinasies in vergelyking met dié van individuele plantekstrakte te bepaal. Volgens die TLC-ontleding beskik E. globulus-ekstrakte oor meer verbindings as die ander twee plante in die studie. Vir die bio-outografiese toets het E. globulus en kombinasies daarmee groter stremmingsones as A. crenulata en D. viscosa getoon. In die LC-MS-ontleding het PCA en HCA op ’n hegte verhouding tussen A. crenulata en D. viscosa, D. viscosa en E. globulus, en die drievoudige kombinasie daarvan gedui. Een-en-twintig komponente is in die vlugtige olie van A. crenulata gevind, wat 88,83% van die algehele oliesamestelling uitmaak. Die olie is deur suurstofhoudende monoterpene (46,25%) oorheers. Die vlugtige olie van E. globulus het 26 verbindings opgelewer, wat 95,62% van die oliesamestelling uitmaak. Suurstofhoudende monoterpene (32,98%) het ook die vlugtige olie van E. globulus oorheers. Nóg PCA nóg HCA het op enige beduidende variasie in die metaboliete van die vlugtige olies van die individuele plante en hul kombinasies gedui. Die verhoogde in vitro- antimikrobiese aktiwiteit en farmakologiese interaksies (sinergie en additiwiteit) in van die kombinasies (dubbel én drievoudig) wat in hierdie studie getoets is, bied wetenskaplike stawing vir die gebruik van medisinale plantkombinasies in Wes-Kaapse tradisionele geneeskunde. Die metaboliese profiele van plantkombinasies kan verander weens die interaksie van die verskillende bioaktiewe plantmolekules, en kan baie bepaalde antimikrobiese aktiwiteit tot gevolg hê.
49

An investigation into the use of artificial intelligence techniques for the analysis and control of instrumental timbre and timbral combinations

Antoine, Aurélien January 2018 (has links)
Researchers have investigated harnessing computers as a tool to aid in the composition of music for over 70 years. In major part, such research has focused on creating algorithms to work with pitches and rhythm, which has resulted in a selection of sophisticated systems. Although the musical possibilities of these systems are vast, they are not directly considering another important characteristic of sound. Timbre can be defined as all the sound attributes, except pitch, loudness and duration, which allow us to distinguish and recognize that two sounds are dissimilar. This feature plays an essential role in combining instruments as it involves mixing instrumental properties to create unique textures conveying specific sonic qualities. Within this thesis, we explore harnessing techniques for the analysis and control of instrumental timbre and timbral combinations. This thesis begins with investigating the link between musical timbre, auditory perception and psychoacoustics for sounds emerging from instrument mixtures. It resulted in choosing to use verbal descriptors of timbral qualities to represent auditory perception of instrument combination sounds. Therefore, this thesis reports on the developments of methods and tools designed to automatically retrieve and identify perceptual qualities of timbre within audio files, using specific musical acoustic features and artificial intelligence algorithms. Different perceptual experiments have been conducted to evaluate the correlation between selected acoustics cues and humans' perception. Results of these evaluations confirmed the potential and suitability of the presented approaches. Finally, these developments have helped to design a perceptually-orientated generative system harnessing aspects of artificial intelligence to combine sampled instrument notes. The findings of this exploration demonstrate that an artificial intelligence approach can help to harness the perceptual aspect of instrumental timbre and timbral combinations. This investigation suggests that established methods of measuring timbral qualities, based on a diverse selection of sounds, also work for sounds created by combining instrument notes. The development of tools designed to automatically retrieve and identify perceptual qualities of timbre also helped in designing a comparative scale that goes towards standardising metrics for comparing timbral attributes. Finally, this research demonstrates that perceptual characteristics of timbral qualities, using verbal descriptors as a representation, can be implemented in an intelligent computing system designed to combine sampled instrument notes conveying specific perceptual qualities.
50

Is auditing useful in avoiding polypharmacy?

Ng, Wing-yiu, George., 吳榮耀. January 2005 (has links)
published_or_final_version / Community Medicine / Master / Master of Public Health

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