Diseases associated with amyloid aggregation have been a growing focus of medical research in recent years. Altered conformations of amyloidogenic peptides assemble to form soluble aggregates that deposit into the brain and spleen causing disorders such as Alzheimer's disease and Type II diabetes. Emergent theories predict that fibrils may not be the toxic form of amyloidogenic structures and that smaller oligomer and protofibril aggregates may be the primary source of cellular function damage. Studies show that these amyloidogenic aggregates are characterized by an increased number of poorly dehydrated hydrogen backbones and large surface densities of patches of bulk like water which favor protein association. When proteins aggregate to form larger structures, there is a redistribution of water surrounding these proteins. The water dynamics of amyloidogenic aggregation is different than the monomeric form and has a decrease in the number of patches occupied by molecules with bulk-like water behavior. We demonstrate that the redistribution of water during amyloid aggregation is reflected in a change in the dielectric relaxation signal of protein-solvent mixtures. We use dielectric relaxation spectroscopy (DRS) as a tool for studying the dynamics of amyloidogenic peptides--amyloid beta (Ab 1-42) and human islet amyloid polypeptide (hIAPP)--during self-assembly and aggregation. Non-amyloidogenic analogs-- scrambled (Ab 42-1) and rat islet amyloid polypeptide (rIAPP)--were used as controls. We first present studies of amyloidogenic peptides in a deionized water buffer at room temperature as a function of concentration and incubation time. From this we were able to determine differences in amyloidogenic and non-amyloidogenic peptides through the dielectric modulus. We next present the same analytes in a deionized water-glycerol buffer to facilitate the study of the dielectric permittivity at sub-freezing temperatures and model the kinetics of the alpha- and beta- relaxation processes. We conclude our work by studying the peptides in a bovine serum albumin (BSA) and glycerol buffer to demonstrate dielectric spectroscopy as a sensitive tool for measuring amyloidogenic peptides in an in vivo- like condition.

Personalised medicine is widely considered to be the future of global healthcare, where diagnosis, treatment, and potentially even drug development, will become specific to, and optimised for, each individual patient. Traditional population based cell studies suppress the influence of outlier cells that are frequently those of most clinical relevance. Hence single-cell analysis is becoming increasingly important in understanding disease, aiding diagnosis and selecting tailored treatment; but remains the preserve of biomedical laboratories far from the patient. Current instruments depend upon cell-labelling to identify the cell type(s) of interest, which require that these be chosen a-priori and may not be those most clinically relevant. Furthermore, cell-labelling is fundamentally subjective, requiring highly-skilled operators to decide upon the validity of each and every test. Therefore, new test methods need to be developed to enable the widespread adoption of single-cell analysis. The passive electrical properties of biological cells are known to be indicative of the specific cell type, but no technology has demonstrated their comprehensive measurement within a mass-manufacturable device. This work aims to show that biologically meaningful information can be obtained in the form of identifiable “cell signatures” through broadband frequency measurements spanning 100 kHz to 100 MHz that exploit the properties of differential electric fields. This hypothesis is tested through the design, implementation and experimental testing of a dedicated microsystem that integrates two novel designs of electrical sensor within a standard, mass-manufacturable Complementary Metal-Oxide Semiconductor microelectronics technology. One sensor measures the absolute electrical environment above a single sense electrode. The other measures the difference in electrical environment between a pair of electrodes, with view to provide information regarding the suspended cell only, through rejecting the common signal due to its suspending medium. Both sensors are shown capable of detecting individual biological cells in physiological solution, and the differential sensor capable of identifying individually-fixed red blood cells, cervical cancer HeLa cells, and three diameters of homogeneous polystyrene micro-beads of comparable size, all while suspended in physiological saline. These results confirm the hypothesis that differential electric fields provide greater distinction of suspended cells from their environment than existing electrical methods. This finding shows that electrode polarisation arising from proximity to liquids, and particularly physiological media, can be overcome through fully-differential electrical cell sensing. However, misalignment between cells and sensor electrodes limits the sensitivity achieved with the microsystem. Methods to overcome such alignment issues should be investigated in future work, along with higher frequency measurements beyond those presented here.

No description available.

Orientador: Marcos Augusto de Lima Nobre / Banca: André Farias de Moura / Banca: Ana Maria Pires / Resumo: Neste trabalho foi realizado o estudo das propriedades espectroscópicas e dielétricas de blendas de biodiesel/diesel, o que permitiu a identificação de um conjunto de parâmetros necessários à análise de interações moleculares. O Biodiesel utilizado foi o produzido a partir do óleo de soja. As interações moleculares foram identificadas pelas propriedades em excesso. Uma visão ampla das propriedades em excesso foram descritas por uma série de blendas biodiesel / diesel a partir da análise molecular intrínseca (infravermelho) e análise do bulk (impedância dielétrica) de fluidos. As ligações químicas foram investigadas pela técnica de espectroscopia no infravermelho. A partir desta técnica foi possível estudar a interação molecular pelo deslocamento de pico, o deslocamento da área do pico, a constante de força da ligação (modelo do oscilador harmônico) em função do teor de biodiesel em cada blenda. Como exemplo, a evolução da banda em 1742 cm -1 característica da ligação C = O é sensível a uma variação do teor de biodiesel na blenda. Propriedades do bulk dos fluidos e misturas foram investigados por meio de medidas elétricas e dielétricas. As medidas foram realizadas por espectroscopia de impedância e dielétrica. O semicírculo de impedância foi modelado utilizando um circuito elétrico equivalente com resistência e capacitância associados em paralelo. Tal abordagem permite extrair os seguintes parâmetros em cada mistura: a resistência elétrica (R),a capacitância (C), e mais frequente... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: In this work both spectroscopical and dielectrical properties of blends of biodiesel/diesel were studied, which allowed the determination of a set of parameters from which It was possible to detect molecular interactions. Biodiesel was made from soybean oil. Such molecular interactions have been identified from classical ―Excess Proprieties‖. A broad view of this excess properties were described for a serie of biodiesel/diesel blends steaming from intrinsic molecular analysis (infrared) and bulk analysis (dielectric impedance) of fluids. Chemical bonds were investigated by the infrared spectroscopy technique. From this technique It was possible to study molecular interaction by the peak displacing, peak area distortion, changing of bond strength (harmonic oscillator theory) at particular vibration, as a function of content of biodiesel at each blend. As an example, the evolution of the band in 1742 cm -1 characteristic of C=O bond is sensitive to a variation of the biodiesel content in the blend. The apparent strength of the bond, k, was determined. Bulk properties of fluids and blends were investigated by both electrical and dielectrical measurements. Measurements were carried out by impedance and dielectric spectroscopy. The impedance semicircle was modeled using an equivalent electrical circuit with resistance and capacitance associated in parallel. Such approach allows to derive following parameters at each blend: electric resistance (R) capacitance (C), most frequent relaxation frequency (fo). The dielectric permittivity for biodiesel, diesel and blends were derived. The value derived at 1 MHz for diesel and biodiesel was equal to 3.8 and 4.3, respectively. The electrical conductivity of diesel and biodiesel was... (Complete abstract click electronic access below) / Mestre

Self-assembly and the induced orientation of microscopic biological systems is of great scientific interest, because it holds the promise of many pharmaceutical applications. This dissertation presents experimental studies done on proteins, short DNA fragments, and cholesterol structures self-assembled in an aqueous environment. The goal is to probe the thermo-physical properties of these systems, their phases and phase transitions, in order to better under-stand the principles behind their unique assemblies and function. It is accepted that in all these systems the solvent water plays an important role on the assembly folding, orientation, and activity of biopolymers. However, the abundance of water in typical samples presents many experimental challenges. It is indeed the case that changes in the properties of hydration in watery environments are responsible for the dynamics of protein and DNA biomolecules. We have explored in more detail the thermodynamics, the structural properties, and the dynamics near structural transitions of biomolecules in their native aqueous environment.

When polymer power cables were introduced into mediumvoltage applications in the late 1960s, the degradationphenomenon later referred to aswater treeingwas still unknown. However, this changedwithin a relatively short space of time. Just 5-10 years afterthese first polymer applications, faults began to appear thatcould be attributed to the new phenomenon-water treeing. Sincethen, cable manufacturers have been improving their designsgradually, and cables produced today are assumed to have muchlower susceptibility to water trees. However, water treeing isstill assumed to be the most important degradation process inthese applications. There are huge amounts of polymer cable installations thatare degraded by water trees. Since many of these cables areinstalled in the same grid nets, one cable fault oftengenerates another. If two or more cables fail at the same time,the consequences can be extensive. A non-destructive diagnosticmethod makes it possible to assess cables and take action priorto failures. This thesis presents the results of research work on thedevelopment of a measurement technique and diagnostic methodfor the assessment of medium voltage XLPE cables in the field.The method used is called high voltage dielectric spectroscopy,and involves the measurement of capacitance and loss as afunction of frequency at high voltages. The method is used in ashort frequency range of approximately one decade in thelow-frequency region (normally from 1 down to 0.1 Hz). Thevoltage levels used initially are all below the service-voltagelevel. If the cable is assessed to be free from water trees, aslightly increased voltage can be used. Based on dielectric-spectroscopy measurements, specificwater-tree analysis and breakdown tests, a set of measurementprocedures and criteria that take into account differences incable designs has been proposed for the assessment of mediumvoltage XLPE cables. The characteristic responses of XLPEcables (in both non and water-tree-deteriorated cases) make itpossible to separate the cable response from the influence ofaccessories. Field experience shows thatwater-tree-deteriorated cables with relatively low breakdownstrengths can remain in service for many years. <b>Keywords:</b>dielectric spectroscopy, high voltage,variable frequency, diagnostics, non-destructive diagnostics,cables, medium voltage, polymer, XLPE, water trees, watertreeing

<p>When polymer power cables were introduced into mediumvoltage applications in the late 1960s, the degradationphenomenon later referred to as<i>water treeing</i>was still unknown. However, this changedwithin a relatively short space of time. Just 5-10 years afterthese first polymer applications, faults began to appear thatcould be attributed to the new phenomenon-water treeing. Sincethen, cable manufacturers have been improving their designsgradually, and cables produced today are assumed to have muchlower susceptibility to water trees. However, water treeing isstill assumed to be the most important degradation process inthese applications.</p><p>There are huge amounts of polymer cable installations thatare degraded by water trees. Since many of these cables areinstalled in the same grid nets, one cable fault oftengenerates another. If two or more cables fail at the same time,the consequences can be extensive. A non-destructive diagnosticmethod makes it possible to assess cables and take action priorto failures.</p><p>This thesis presents the results of research work on thedevelopment of a measurement technique and diagnostic methodfor the assessment of medium voltage XLPE cables in the field.The method used is called high voltage dielectric spectroscopy,and involves the measurement of capacitance and loss as afunction of frequency at high voltages. The method is used in ashort frequency range of approximately one decade in thelow-frequency region (normally from 1 down to 0.1 Hz). Thevoltage levels used initially are all below the service-voltagelevel. If the cable is assessed to be free from water trees, aslightly increased voltage can be used.</p><p>Based on dielectric-spectroscopy measurements, specificwater-tree analysis and breakdown tests, a set of measurementprocedures and criteria that take into account differences incable designs has been proposed for the assessment of mediumvoltage XLPE cables. The characteristic responses of XLPEcables (in both non and water-tree-deteriorated cases) make itpossible to separate the cable response from the influence ofaccessories. Field experience shows thatwater-tree-deteriorated cables with relatively low breakdownstrengths can remain in service for many years.</p><p><b>Keywords:</b>dielectric spectroscopy, high voltage,variable frequency, diagnostics, non-destructive diagnostics,cables, medium voltage, polymer, XLPE, water trees, watertreeing</p>

Made available in DSpace on 2014-06-11T19:29:06Z (GMT). No. of bitstreams: 0 Previous issue date: 2011-11-23Bitstream added on 2014-06-13T19:17:18Z : No. of bitstreams: 1 brito_iao_me_sjrp.pdf: 2547892 bytes, checksum: 97dc4b0c58e44692a47f09742af55178 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Neste trabalho foi realizado o estudo das propriedades espectroscópicas e dielétricas de blendas de biodiesel/diesel, o que permitiu a identificação de um conjunto de parâmetros necessários à análise de interações moleculares. O Biodiesel utilizado foi o produzido a partir do óleo de soja. As interações moleculares foram identificadas pelas propriedades em excesso. Uma visão ampla das propriedades em excesso foram descritas por uma série de blendas biodiesel / diesel a partir da análise molecular intrínseca (infravermelho) e análise do bulk (impedância dielétrica) de fluidos. As ligações químicas foram investigadas pela técnica de espectroscopia no infravermelho. A partir desta técnica foi possível estudar a interação molecular pelo deslocamento de pico, o deslocamento da área do pico, a constante de força da ligação (modelo do oscilador harmônico) em função do teor de biodiesel em cada blenda. Como exemplo, a evolução da banda em 1742 cm -1 característica da ligação C = O é sensível a uma variação do teor de biodiesel na blenda. Propriedades do bulk dos fluidos e misturas foram investigados por meio de medidas elétricas e dielétricas. As medidas foram realizadas por espectroscopia de impedância e dielétrica. O semicírculo de impedância foi modelado utilizando um circuito elétrico equivalente com resistência e capacitância associados em paralelo. Tal abordagem permite extrair os seguintes parâmetros em cada mistura: a resistência elétrica (R),a capacitância (C), e mais frequente... / In this work both spectroscopical and dielectrical properties of blends of biodiesel/diesel were studied, which allowed the determination of a set of parameters from which It was possible to detect molecular interactions. Biodiesel was made from soybean oil. Such molecular interactions have been identified from classical ―Excess Proprieties‖. A broad view of this excess properties were described for a serie of biodiesel/diesel blends steaming from intrinsic molecular analysis (infrared) and bulk analysis (dielectric impedance) of fluids. Chemical bonds were investigated by the infrared spectroscopy technique. From this technique It was possible to study molecular interaction by the peak displacing, peak area distortion, changing of bond strength (harmonic oscillator theory) at particular vibration, as a function of content of biodiesel at each blend. As an example, the evolution of the band in 1742 cm -1 characteristic of C=O bond is sensitive to a variation of the biodiesel content in the blend. The apparent strength of the bond, k, was determined. Bulk properties of fluids and blends were investigated by both electrical and dielectrical measurements. Measurements were carried out by impedance and dielectric spectroscopy. The impedance semicircle was modeled using an equivalent electrical circuit with resistance and capacitance associated in parallel. Such approach allows to derive following parameters at each blend: electric resistance (R) capacitance (C), most frequent relaxation frequency (fo). The dielectric permittivity for biodiesel, diesel and blends were derived. The value derived at 1 MHz for diesel and biodiesel was equal to 3.8 and 4.3, respectively. The electrical conductivity of diesel and biodiesel was... (Complete abstract click electronic access below)

Epoxy resins are widely used materials in the industry as electrical insulators, adhesives and in aircrafts structural components because of their high mechanical stiffness, strength and high temperature and chemical resistance properties. But still, the influence of water uptake due to moisture adsorption is not fully understood as it detrimentally modifies the electrical and chemical properties of the material. Here ,we investigate the influence of water moisture uptake on the neat epoxy material by monitoring the change in the volume resistivity and dielectric properties of epoxy material at three different thickness configurations: 0.250 mm, 0.50 mm and 1 mm thicknesses. Gravimetric analysis was done to monitor the mass uptake behaviour, Volume Resistivity was measured to monitor the change in conductivity of the material, and the dielectric properties were mapped to characterise the type of water mechanism available within the material during two ageing processes of sorption and desorption. Two-stage behaviours of diffusion and reaction have been identified by the mass uptake analysis. Moreover, the plot of volume resistivity versus mass uptake has indicated a non-uniform relationship between the two quantities. However, the analysis of the dielectric spectrum at medium range of frequency and time has showed a change in the dipolar activities and also showed the extent to which the water molecules can be segregated between bounding to the resin or existing as free water

No description available.