Made available in DSpace on 2014-06-11T19:29:08Z (GMT). No. of bitstreams: 0 Previous issue date: 2012-10-22Bitstream added on 2014-06-13T20:38:25Z : No. of bitstreams: 1 santos_al_me_araiq.pdf: 1374698 bytes, checksum: 4000b6c44028dbd65db8795f30a87ff5 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / O presente trabalho está baseado no desenvolvimento de um sistema biomimético para monitoramento sensível e seletivo do metabólito TCP (3,5,6-tricloro-2-piridinol), proveniente do agrotóxico clorpitifós, o qual é mais solúvel que o próprio agrotóxico e cuja ocorrência em águas subterrâneas e superficiais é mais provável e perigosa. Foi construído um sensor biomimético com detecção voltamétrica por onda quadrada, os eletrodos, foram confeccionados à base de pasta de carbono modificada com o complexo cloro-5,10,15,20-tetraquis(pentafluorofenil)-21H,23H-porfirina ferro (III), o qual apresenta uma estrutura química semelhante à do sítio ativo da enzima P450. O sensor construído apresentou as melhores respostas em tampão fosfato 0,20 mol L-1 e pH 6,0, usando a voltametria de onda quadrada a 50 Hz, 150 mV de amplitude e 1,5 mV de E. Com os parâmetros otimizados o sensor apresentou limites de detecção e de quantificação de 1,9 e 5,2 μmol L-1, respectivamente. Estudos realizados para averiguar a biomimeticidade do sensor, incluíram: velocidade de varredura por voltametria cíclica, exploração do perfil hiperbólico da resposta no sensor e avaliação da seletividade. O sensor foi satisfatoriamente usado na análise em diversos tipos de amostras de interesse ambiental. Foram feitos testes de recuperação e nas amostras de solo, águas superficiais e subterrâneas obtendo recuperação de 91%, 107% e 96% respectivamente, mostrando que o sensor pode ser usado como método alternativo para quantificação de TCP em diferentes matrizes. O sensor também foi empregado no monitoramento da eficiência de polímeros de impressão molecular (MIP) para TCP. Buscando obter o polímero biomimético mais eficiente para o analito, foram usadas ferramentas computacionais que permitiram escolher o melhor monômero (acrilonitrila)... / This work is based on developing a biomimetic system for sensitive and selective monitoring of the TCP (3,5,6-trichloro-2-pyridinol), the principal metabolite of the pesticide chlorpyrifos, which is more soluble than the pesticide and whose occurrence in groundwater and surface water is more likely and dangerous. For this, a biomimetic sensor was constructed and the square wave voltammetric was used for measurements. The electrodes were fabricated using carbon paste modified with the complex chloro-5,10,15,20-tetrakis-(pentafluorophenyl)-21H,23H-porphyrin iron(III), which has a chemical structure similar to the active site of the enzyme P450. The sensor presented the best responses in phosphate buffer 0.20 mol L-1 and pH 6.0, using the square wave voltammetry with 50 Hz, amplitude of potential of 150 mV and ΔE of 1.5 mV. With the optimized parameters the sensor showed limits of detection and quantification of 1.9 and 5.2 μmol L-1, respectively. Studies conducted to investigate the mimicking of the sensor, included evaluation of the influence on scan rate in the cyclic voltammetry, the verification of the hyperbolic profile of the sensor response and evaluation of selectivity. The sensor has been satisfactorily applied in the analysis of different samples of environmental interest. Recovery experiments in samples of soil, surface water, and groundwater showed values of 91%, 107% and 96% respectively, showing that the sensor can be used as an alternative method for the quantification of TCP in different matrices. The sensor was also used to monitor the efficiency of molecularly imprinted polymers (MIP) for TCP. In order to obtain the most efficient biomimetic polymer to this analyte were used computational tools that allowed select the best monomer (acrylonitrile). In order to verify the results obtained by the theoretical... (Complete abstract click electronic access below)

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D.Phil. / This dissertation deals with the fabrication, characterisation, and applications of long-period gratings in optical fibre communications and sensing systems. The aim of this project is to assess long-period gratings as media for active or passive fibre devices, particularly as components for the telecommunications industry. A review of the properties and characteristics of fibre gratings associated with the photosensitivity of germanosilicate fibres is provided, which includes a theoretical analysis of the principles of operation for short-period gratings (fibre Bragg gratings) and long-period gratings. The simulations of the spectral response from these two types of gratings are also presented. A number of long-period grating fabrication methods and techniques, which were reported by some researchers, are reviewed. In this project, the normal long-period gratings and phase-shifted long-period gratings are fabricated by using a line-narrowed KrF excimer laser combined with the metal amplitude mask technique. The metal mask is made of a stainless steel sheet, and the slot width (periodicity) is processed by using high quality photographic tooling. Three normal long-period gratings with different periodicities and one phase-shifted long-period grating can be manufactured simultaneously because there are four metal masks imprinted in one inexpensive stainless steel sheet. The mass-production of long-period gratings becomes possible, and the number of gratings that can be written is limited only by the excimer laser beam or metal mask dimension orthogonal to the fibre axis. The fibres that are used in our experiments are photosensitive optical fibres (PS1500). Long-period gratings can be written directly into these fibres without hydrogenation. Two types of long-period grating devices are investigated and developed for applications in dense wavelength division multiplexing (DWDM)networks: erbium-doped fibre amplifier (EDFA) gain-flattening filters and wavelength-tuneable add/drop multiplexers. Firstly, the transmission characteristics of phase-shifted long-period gratings are simulated theoretically by a combination of the coupled-mode theory and the fundamental-matrix method. It is suggested that a phase-shifted long-period grating device cascaded with another normal long-period grating can be used to flatten the gain spectrum of an EDFA containing three gain peaks. The experimental results show that a broad amplifier with peak-to-peak variations of less than 0.7 dB over 36 nm from 1526 to 1562 nm, which covers the entire C-band of the EDFA, can be realized practically. Next, a wavelength-tuneable add/drop multiplexer is designed and configured. In this device, four identical long-period gratings are assembled on piezoelectric ceramic fibre stretchers. The modelling of the device predicts that 50 ITU DWDM-channel signals could be selected in the wavelength range from 1526.25 to 1563.75 nm with 0.75 nm channel spacing and the cross-talk is less than –39 dB while the total insertion loss is about 0.24 dB. There are some significant advantages of wavelength-tuneable add/drop multiplexing devices over conventional fibre Bragg grating-based devices. (1) There is back reflected light and almost no cross-talk power penalty because the long-period grating couples light into forward-propagating modes. (2) Signal channel isolation is very high due to three stages of coupling mechanisms used in this device, which includes core-cladding, cladding-cladding and cladding-core, efficiently filtering out non-resonant light. (3) The insertion loss of the device is limited only by the separation of two long-period gratings, because there are no losses on non-resonant wavelengths of long-period gratings. Several other applications of long-period gratings in optical sensing systems are also described, and some are experimented on including axial strain sensors, structural bend sensors, temperature sensors, refractive index sensors and chemical concentration sensors.

M.Ing. (Electrical And Electronic Engineering) / A need was established for the development of a acoustical sensor in silicon. The acoustical sensor is based on the silicon pressure sensor. This sensor consists of a silicon membrane which is formed from silicon bulk material by means of etching. By transforming the movement of the membrane into a variation of capacitance, it is possible to detect a change in pressure. Signal processing is needed to insure that the : information, received from the sensor, is useable and accurate. The physical aspects of sound was investigated. An important relationship was derived between the intensity of a sound and the pressure associated with it. Because silicon was used in a mechanical environment, the mechanical properties of the material were investigated. A model was developed to simplify the design of the senor. A expression was derived for the movement of the membrane for any uniform load applied to it. The variation in capacitance was given by integrating over the area of the membrane. The condense microphone was used as a example of a design of a acoustical sensor. Arising from the example, the natural frequency of the silicon membrane was looked into. A variety of diaphragms were made to provide for a wide working area. Some of the manufacturingprocesses were individually examincd and changed to comply with the manufacturing of the diaphragms. The important process of etching was thoroughly investigated. An excellent etching agent was found with which accurate micro machining could be done. Using this etching agent, a variety of silicon and poll silicon diaphragms were made. Most of the silicon diaphragms were suceossfully formed. The. poli silicon diaphragms were however deformed because of internal stress which developed during the forming process. A signal processing circuit was developed to perform the task of transforming the variation in capacitance to a variation in voltage. The circuit utilised the current through the capacitor to establish the variation in capacitance. The current was transferred to a voltage by a differencing current amplifier. Further signal processing is done by a analogue multiplier.

D.Ing. / Most optical fibre-based ambient refractive index sensors (including individual long-period gratings) rely on spectral attributes obtained in transmission. However, a probe refractometer has been proposed that is based on self-interference of a long-period grating (LPG), thus providing reflectance spectra containing the relevant data. This sensor operates as a Michelson interferometer by virtue of the fact that its constituent LPG acts as both a mode converter and coupler. Its construction is such that optical power coupled into the cladding (when light impinges on the LPG) is reflected at a fibre mirror and returns towards the grating, where it is re-coupled into the fundamental guided mode. Since light waves propagating along the core and cladding material of the fibre cavity beyond the LPG experience different optical path lengths (due to differing mode indices), a phase difference exists between these modes upon recombining at the grating location. This causes interference, which is manifested as a characteristic fringe pattern in the sensor’s reflectance spectrum (analogous to that obtained in the transmission of a twin LPG cascade operating as a Mach-Zehnder interferometer). Research was conducted towards implementing a unique method of temperature compensation in this LPG-based Michelson interferometer. Sensing attributes of individual LPGs were investigated first, with specific emphasis on the temperature characteristics of two different types of host fibre. It was found that LPGs manufactured in conventional ATC SMF-28 fibre (previously hydrogen-loaded to inscribe the grating and annealed after fabrication) and B/Ge co-doped PS1500 fibre from Fibercore exhibited temperature characteristics of opposite polarity. This led to the implementation of a compound-cavity Michelson interferometer whose constituent LPG is written in one type of fibre, while a specific length of the other type of fibre is fusion spliced onto the host fibre section. Experiments verified the success of this temperature-compensation technique, which caused a measured reduction in temperature sensitivity of up to in interferometer phase shift. Measurements of the refractive index of the test substance surrounding the cladding material of the Michelson interferometer’s fibre cavity (and not the LPG itself) could therefore be done without being adversely affected by environmental temperature fluctuations. This was demonstrated experimentally by comparing the interferometer’s phase shift – devoid of temperature-induced effects – due to increasing refractive index of the analyte (as a result of escalating temperature) with index of refraction readings from a temperature-controlled Abbe refractometer. Numerical gradients of linear curves fitted to these results differed by two orders of magnitude less than the resolution of readings obtained from an Abbe refractometer – proof of the success of the temperature compensation technique applied in this LPG-based Michelson refractometer.

No description available.

Eighty male undergraduate students were randomly assigned to one of five groups in an analogue investigation of crime-intoxication on the physiological detection of deception. Sixty-four of the subjects committed a mock crime and half of these were legally intoxicated during the crime. Sixteen subjects committed no crime and served as innocent controls. Results only partially replicated those of Bradley and Ainsworth (1984). Whereas they found crime-intoxication diminished the effectiveness of both the control question test (CQT) and the guilty knowledge test (GKT), the present study found crime-intoxication diminished the accuracy of the CQT only for certain subjects; those who reported high subjective arousal during the crime. Results showed no alcohol effect on the GKT. In light of their results Bradley and Ainsworth suggested that alcohol may act through emotional or memory processes important to polygraphic examination. In a fully factorial design, the present study investigated the effects of threat during the crime and memory for crime details on polygraph outcome. As well, the effect of alcohol on these "emotion" and memory variables was examined. Memory was found to be an important variable in GKT accuracy but not important to CQT accuracy. Threat, as operationalized for the present investigation, had no effect on either the CQT or the GKT but a component of the threat variable, subjective arousal, was found to affect GKT accuracy but not that of the CQT. Raskin's (1979) two-response model of detection of deception is used to explain the results of this study although the relationship of subjective arousal to polygraph outcome is unclear and requires examination in future studies. / Arts, Faculty of / Psychology, Department of / Graduate

Sixty male undergraduate students participated in an experiment designed to investigate the effects of anti-anxiety and stimulant drugs on polygraphic interrogation. Subjects were randomly assigned to one of four groups. Three of the groups watched a 12 minute videotape depicting the burglary of an apartment through the eyes of the thief. Each subject was asked to imagine that it was he who was committing the crime and was given instructions to encourage his becoming absorbed in the videotape. Afterwards, they were accused of committing this crime. Each subject received one of three look-alike capsules containing a drug which, they were told, would help them to escape detection. Capsules for the first group contained 10 mg of diazepam; those for the second group, 20 mg of methylphenidate; a placebo was given to the third group. Subjects in the fourth group, the innocent control condition, viewed a 10 minute videotape sequence showing the interior of another apartment, this time with no crime committed. They did not receive any medication or placebo after they were accused of committing the crime. After a one hour wait, all subjects were interrogated by the experimenter, who was blind to both their guilt or innocence and drug status. Skin conductance, heart rate and respiration were monitored; all charts were scored blindly. No drug effects were found in the guilt/innocence classification or in any of the physiological channels being monitored. The overall hit rate, including inconclusives, was 81.7%. A significant relationship between recall of guilty information and detectability was also found. / Arts, Faculty of / Psychology, Department of / Graduate