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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.
221

Using de novo design proteins to explore tyrosine radicals and cation-π interactions

Berry, Bruce W. January 2014 (has links)
Redox cofactors and amino-acid free radicals play important roles in biology. Although many of the same cofactors and amino acids that form these radicals are found across a broad range of biological systems, identical cofactors can have different reduction potentials. The local environment plays a role in defining these redox potentials. An understanding of this local-environment effect can shed more light on how redox chemistry works in nature. Our laboratory has developed a library of model proteins that are well suited to study amino-acid radicals. a3X is a de novo designed protein that is composed of 67 residues. It forms a three-helix bundle connected by two glycine loops. The radical site is located at position 32 on the central a-helix. The a3X protein is designed to be well-folded and thermodynamically stable across a broad pH range. Paper 1 describes the structural and electrochemical characterization of a3Y, a tyrosine variant of a3X. We were able to obtain a unique Faradaic response from Y32 at both low and high pH, using differential pulse voltammetry. In addition, we successfully redesigned α3Y by introducing a histidine in close proximity to Y32, creating a tyrosine/histidine pair. Our goal in creating this pair was to study proton-coupled electron transfer (PCET) in a well-structured and solvent-sequestered protein environment.  In paper 2 we illustrated the redox reversibility of Y32 and produced the first ever Pourbaix diagram for a tyrosine radical in a protein. The formal potential of the Y32-OŸ/Y32-OH redox couple was determined to be 918 ± 2 mV vs. the normal hydrogen electrode (NHE) at pH 8.40.  While at pH 5.52, the formal potential of the Y32-OŸ/Y32-OH redox couple was recorded at 1.07 V. Papers 3 and 4 utilize a3W to study cation-π interactions. In paper 3, we showed how solvation can affect the strength of these interactions by -0.9 kcal/mol. In Paper 4, we were able to monitor the disruption of the cation-π interaction with the use of high-pressure fluorescence and were able to calculate the interaction energy for a solvent exposed cation-π. The aim of the work described in this thesis was to use model proteins to study tyrosine radicals to gain a broader perspective and better understanding of the versatility of biological electron transfer and to measure cation-π interactions and how they behave in different environments. / <p>At the time of the doctoral defense, the following paper was unpublished and had a status as follows: Paper 4: Manuscript.</p>
222

A LOW COST 2-AXIS PLC CONTROLLED FILAMENT WINDING MACHINE WITH SIMPLIFIED FIBER WINDING ANGLE AND TENSION CONTROL SYSTEM

Hazra, Trinankur 17 March 2011 (has links)
Designing a filament winding machine involves two major components. First component is the designing of the mechanism which delivers appropriate winding pattern as specified by the user (i.e. the winding angle). The second component is the realization of an effective fiber tensioning system for ensuring consistent overall consolidation. Today, there exist a variety of sophisticated methods to achieve both these parameters; however the implementation of these techniques increases the price of a winding machine, making its acquisition very difficult for small scale applications. Sophisticated winding machine includes higher number of degrees of freedom, and high end CNC controlled algorithms. However for creating axi-symetric products with constant diameter, only a 2-axis winding is sufficient. On this note a novel cost effective method for fiber winding angle control and fiber winding tension control is designed, simulated, implemented into a low cost prototype 2-axis filament winding machine, and the scope for its? further improvement has also been discussed. The system designed, uses a cost effective PLC as the centralized controller of the system for implementing both fiber winding control and tension control through PID control. A novel actuator for tension control is designed and implemented. Also a comparison between the conventional PI controller and a Mamdani type Fuzzy inference based control system for controlling the fiber tension is made. In this process a novel technique for making PI controller capable of handling known nonlinearities in the system is introduced. Experimental system responses of the designed prototype are analyzed.
223

Dynamic Tuning of PI-Controllers based on Model-free Reinforcement Learning Methods

Abbasi Brujeni, Lena Unknown Date
No description available.
224

Vibrational and Theoretical Investigations of Molecular Conformations and Intramolecular pi-Type Hydrogen Bonding

Ocola, Esther 2011 December 1900 (has links)
The molecular conformations, potential energy functions and vibrational spectra of several cyclic molecules have been investigated by ab initio and density functional theory calculations and by infrared and Raman spectroscopy. The ab initio computations of 3-cyclopenten-1-ol predict that its lowest energy conformer has a weak pi-type intramolecular hydrogen bonding. The three other conformers lie 301 to 411 cm^-1 higher in energy. The infrared and Raman spectra of this molecule confirm the presence of the four conformers. The energy difference between the two conformers of lowest energy was also determined from the experimental spectroscopic data and was found to be 435 plus/minus 160 cm^-1, in reasonable agreement with the ab initio computations results. Ab initio calculations for cyclopentane and d1, 1,1-d2, 1,1,2,2,3,3-d6, and d10 isotopomers confirm cyclopentane confirmed that has twist and bent structures and that these differ in energy by less than 10 cm^-1. The bending angle is 41.5 degrees and the twisting angle is 43.2 degrees. A complete vibrational assignment for each of the isotopomers was achieved. Ab initio calculations were also carried out for methylcyclopropane, cyclopropylsilane, cylopropylgermane, cyclopropylamine, cyclopropanethiol and cyclopropanol. The structure and the potential energy function for internal rotation was calculated for each and compared to available experimental results determined from infrared and Raman spectra. The calculated barriers to internal rotation agree very well with the experimental data. The structures, relative energies, and frequencies for the lowest energy vibrations of the twisted, bent, and planar forms of cyclohexene and four of its oxygen analogs were calculated and compared to experimental results. The calculated structural data agree very well with that from the microwave work, but the computed barriers are somewhat lower than those based on far-infrared data. 4-Silaspiro-(3,3)-heptane possesses two four-membered rings, each puckered with and angle of 34 degrees. The molecule possesses a two-dimensional ring-puckering potential energy surface with four equivalent minima. The ab initio calculations predict a barrier to planarity of each ring of 582 cm^-1 while the energy of the structure with both rings planar is 1220 cm^-1 higher. The calculated infrared and Raman spectra were compared to those previously published, and the agreement is excellent.
225

SYNTHESIS AND CHARACTERIZATION OF FUNCTIONALIZED NAPHTHALENES AND ANTHRACENES

Zhang, Guang 01 January 2012 (has links)
Organic electronics have received significant development in the last few decades. p- Type materials are much more in availability than n-type now. There are only a few examples of air-stable n-type materials. The design and synthesis of novel air-stable ntype materials is still a focus of research. Herein is described a study to evaluate the effectiveness of a novel electron-withdrawing group, composed of three electronwithdrawing groups connected in series, to impart material properties known to be favorable for obtaining air-stable n-types. The smaller acenes, naphthalene and anthracene, carrying these electron-withdrawing groups were prepared and studied by UV-Vis absorption spectroscopy and solution electrochemical measurements to estimate changes in frontier molecular orbital energies and single crystal X-ray diffraction to determine packing motif. These measurements suggest that the new materials could be promising as n-type semiconductors in organic field effect transistor (OFET) and as acceptors for organic photovoltaic (OPV) cells. The reasons are based on: (1) the close intermolecular contacts seen in X-ray crystal structures, some of them showing 3D faceto- face stack. (2) Electrochemical measurements indicate LUMO energy levels suitable for air-stable n-type materials.
226

Chinese texts, Western analysis : from film to novel

Tei, Chiew Siah January 2007 (has links)
This study explores perceptions of Chinese texts by Western audiences while looking into the interrelation between film and literature. This is done by two means: firstly, through a detailed discussion of film adaptations with the focus on Chinese cinema, and secondly, through a practical demonstration of a filmic style in prose fiction in the form of an original book-length piece of fiction. Using Bakhtin’s ‘dialogism’ as the point of departure, the research on adaptations adopts an intertextual approach of adaptation theory as developed by Robert Stam, looking into the intertextual relationship between a hypotext (a source text) and a hypertext (film adaptation). The analysis of Raise the Red Lantern by Zhang Yimou (1991) and Crouching Tiger, Hidden Dragon by Ang Lee (2001) concludes that both films contain elements of familiarity and strangeness for Western audiences, an uneasy mix of intimacy and exoticism which underpins their appeal. However, this phenomenon is unintended by the filmmakers themselves, chiefly because, firstly, the directors’ exposure to Western film art has contributed to the use of techniques that are familiar to Western audiences in the making of their films, and, secondly, the elements of strangeness are related to the natures of the films, the cultural elements involved and the locations in which the films are made, which are unfamiliar to a Western audience. The writing of the novel, Little Hut of Leaping Fishes, reveals the necessity of incorporating cultural elements into a narrative that is set in a time and place where the culture is deeply rooted. My background as a fourth-generation Chinese in Malaysia informs my urge as an artist and critic to explore aspects of my own cultural identity. The main concern, which is the key discovery of this experiment, is that once a writer understands the shared creative mechanism between film and literature, he can place a camera before his pages to capture the scenes he carefully arranged, making the page a screen onto which images as well as words can be projected.
227

Fjärrstyrning av värmepump 2.0

Olsson, Henrik, Stensson, Peter January 2014 (has links)
Fjärrstyrning av värmepumpar är en bekvämlighet för att slippa vara på plats och ändå kunna göra inställningar på sin värmepump. Det ger möjligheten att komma till ett förvärmt fritidshus eller stuga med några enkla knapptryckningar. Det ger också möjligheten till mer kontroll över pumpens energiförbrukning, man kan spara in pengar på att inte låta pumpen stå och slösa energi då man inte är på plats. I dagsläget finns flera fjärrstyrningsprodukter för värmepumpar på marknaden, men dessa är ofta dyra och kan oftast bara ansluta till mobilnätet eller wifi. Fjärrstyrningsprodukterna är speciellt framtagna för att styra en värmepump och kan ej användas för att styra ytterligare produkter. Målet med detta examensarbete är att ta fram ett system baserat på en standardplattform som åtgärdar dessa problem samt där det finns möjlighet till framtida utbyggnad av dess funktionalitet. Vi börjar med att bestämma funktionaliteten för vår fjärrstyrningsprodukt. Därefter tas en struktur för hela systemet fram. Efter detta görs val av hårdvara och mjukvaruutveckling. Resultatet av vårt examensarbete är en fjärrstyrningsprodukt som kan styra Daikins värmepumpar. Vår fjärrstyrningsprodukt kan använda 3G-nätet, wifi eller trådat nätverk för att kommunicera med vårt systems centralenhet och användaren. Vår produkt har även en stor potential till utbyggnad för fjärrstyrning eller övervakning av andra enheter i hemmet.
228

New Multi-Objective Optimization Techniques and Their Application to Complex Chemical Engineering Problems

Vandervoort, Allan 18 February 2011 (has links)
In this study, two new Multi-Objective Optimization (MOO) techniques are developed. The two new techniques, the Objective-Based Gradient Algorithm (OBGA) and the Principal Component Grid Algorithm (PCGA), were developed with the goals of improving the accuracy and efficiency of the Pareto domain approximation relative to current MOO techniques. Both methods were compared to current MOO techniques using several test problems. It was found that both the OBGA and PCGA systematically produced a more accurate Pareto domain than current MOO techniques used for comparison, for all problems studied. The OBGA requires less computation time than the current MOO methods for relatively simple problems whereas for more complex objective functions, the computation time was larger. On the other hand, the efficiency of the PCGA was higher than the current MOO techniques for all problems tested. The new techniques were also applied to complex chemical engineering problems. The OBGA was applied to an industrial reactor producing ethylene oxide from ethylene. The optimization varied four of the reactor input parameters, and the selectivity, productivity and a safety factor related to the presence of oxygen in the reactor were maximized. From the optimization results, recommendations were made based on the ideal reactor operating conditions, and the control of key reactor parameters. The PCGA was applied to a PI controller model to develop new tuning methods based on the Pareto domain. The developed controller tuning methods were compared to several previously developed controller correlations. It was found that all previously developed controller correlations showed equal or worse performance than that based on the Pareto domain. The tuning methods were applied to a fourth order process and a process with a disturbance, and demonstrated excellent performance.
229

Keats, Shelley and Byron in Nāzik al-Malāʼikah's poetry

Abdul-Razāk, Hanāʼ Muḥammad January 1989 (has links)
The main purpose of this thesis is to trace the impact of the English Romantic poets, especially Keats, Shelley and Byron, on Arab/Iraqi Romantic poetry and thought, in particular that of Nazik al-Mala'ikah. The thesis is divided into two volumes. The first volume consists of three chapters, each divided into short sections. The first chapter is a detailed introduction to the three other chapters. It discusses the problem of defining the term 'Romanticism'. It studies comparatively the four fundamentals of the English and Arabic Romantic theories. It traces the origin and the development of Arabic/Iraqi Romanticism. It also traces the sources of Nazik's knowledge of world literature: Arabic, English, American, French, German, Greek, Latin and Scandinavian. Nazik's poems and those of other Arabic Romantic poets, such as Iliyya Abu Madi, Ali Mahmud Taha, and Abu 'l-Qasim 'l-Shabbi are compared. The importance of the poems that appear in The Golden Treasury to Arabic poetry in general and to Nazik's poetry in particular is highlighted. A list of English poets, such as Shakespeare, Milton, Gray, Coleridge, Wordsworth, Keats, Shelley and Byron, whose poems and thoughts are influential on Nazik's poetry and critical works, is arranged chronologically with a short introduction to each poet, and his posit ion in Arabic/Iraqi poetry in general and in Nazik's literary works in particular. Abdul-Hai's bibliography of the Arabic versions of English poetry and Jlhan's Ra'uf's bibliography of the Arabic versions of Shelley's poetry are given, in order to indicate the earliest possible date of Arabic translation from English poetry. The second chapter is divided into two parts. These parts are preceded by a short introduction on Arabic translation of English poetry, followed by a section on Nazik's motives in translating English poetry. In the first part, Arabic versions of Gray's Elegy by Andraus, Mahmud, al-Muttalibi and Nazik are analysed comparatively to establish whether Nazik's version is original or dependent on the other earlier Arabic versions. In the final section, the influence of Gray's Elegy on Nazik's themes and imagery is traced. In the second part of this chapter, Nazik's version of Byron's address to the ocean in the fourth canto of Childe Harold's Pilgrimage is fully analysed, preceded by a list of Arabic versions of Byron's poems. Nazik's version is studied independently from other Arabic versions, because most of the versions found are of different parts of Byron's poem. A section is devoted to Nazik's and Byron's relationship with the sea. In the last section, the impact of this passage on Nazik's poetry is traced and compared to that of Gray's Elegy. The third chapter traces the presence of Keats's odes in Nazik's poetry. This chapter is introduced by a definition of the term 'Ode'. The second section traces the impact of the themes and imagery of Keats's odes on Nazik' s poetry. Four sections are devoted to establishing the common contrasting themes in Keats's and Nazik's poetry. The following sections are devoted to the natural elements common to the poetry of Nazik and Keats: the birds, the wind, the river, the sun and the moon. The final sections study comparatively Nazik's and Keats's common literary devices: Personification, Synaesthesia and Compound adjectives. The second volume consists of the fourth chapter, the tables and the bibliography. This chapter studies the allusions in Nazik's poetry, and traces their sources in Keats, Shelley, Byron and Anatole France. A section is devoted to names alluded to in Nazik's poetry. The significance of The Golden Bough in Arabic is highlighted in a separate section, followed by a section on Nazik's mythological themes and symbols. Two sections are devoted to the relations of the Jinniyyah to poetry and to god. The appearance and functions of Nazik's Jinniyyah are compared to those of similar figures in Anatole France and Shelley. Nazik's Jinniyyah is seen as the synthesis of a complex mythological tradition. Many examples are given to discuss her relations to: (1) male and female mythological, religious and cultural characters, such as: Adam, Cain, Abel, Prometheus, Christ, Muhammad, Paphnutius, Midas, Plutus, Eve, Thais, Adonis, Cupid, Narcissus, Nessus, Ares, Magdalen, Thais, Venus, Diana, Rabiah al-Adawiyyah, the Sleeping Beauty, Demeter, Rapunzel and Shahrazad; (2) supernatural creatures, such as: the serpent, the demon, the spider, the sirens, the giant fish, the ghosts and the ghoul; (3) mythological things, such as: the Labyrinth, Lethe, Eldorado, Pactolus and al-Kawthar. A section is devoted to the symbol of Gold in Nazik's and in English poetry. Nine tables are supplied, setting out the common mythological names that occur in Nazik's, Keats's, Shelley's and Byron's poetry. A bibliography of primary and secondary Arabic and English sources is given. This bibliography contains the works cited throughout and other relevant secondary sources. The former are marked with an asterisk.
230

"Education is the key of life" : A Minor Field Study about the discourses of parental involvement in two Tanzanian primary schools

Widell, Karin, Hanna, Tornblad January 2014 (has links)
In Tanzania, the enrolment in school is high but the students’ performance is in general low. Parents are seen as important agents to provide students with opportunities to succeed in school. It is therefore of interest to investigate what is being said about parental involvement (PI) in the Tanzanian school. The aim with this study is to identify and analyse common assumptions about PI in the context of the Tanzanian primary school. We had the opportunity to travel to Tanzania for eight weeks to investigate this. Qualitative semi-structured interviews with eight parents and two teachers about PI were carried out in two rural villages. Questions to the parents about their perception of education were furthermore asked in order to achieve a background for their statements about PI. The study is based on a discourse analytical approach, meaning that the result was obtained through identifying discourses by analysing the respondents’ statements. The analysis resulted in five discourses: Education for the future, PI as a resource, PI as pressures from teachers, PI as a lack of education and PI as paying attention to children’s education. The contents which fill the discourses are discussed in relation to the context of the study as well as perception of the relationship between home and school. The parents in this study value education highly and their involvement is mostly about contributing with financial support. Yet, the teachers are demanding a higher involvement from parents. The low socioeconomic background is a barrier for many parents to become involved. A conscious effort, aimed at getting parents more involved, is needed in order to increase the children’s academic performance.

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