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Master's Dissertation
DOI
https://doi.org/10.11606/D.54.1978.tde-10032015-164420
Document
Author
Full name
Sylvio Quezado de Magalhaes
Institute/School/College
Knowledge Area
Date of Defense
Published
São Carlos, 1978
Supervisor
Committee
Oliveira, Sergio Mascarenhas (President)
Nascimento, Otaciro Rangel
Qualifik, Paul
Title in Portuguese
Dna : bioelétreto, ferroeletricidade e não linearidade
Keywords in Portuguese
Não disponível
Abstract in Portuguese
Utilizando-se as técnicas de Corrente Termoestimulada, Pressão Termoestimulada e Decaimento Isotérmico de Polarização, estudou-se o comportamento de bioeletreto das fibras de sal de sódio do ácido desoxiribonucleico (DNA). A formação do bioeletreto é atribuída a cargas espaciais do DNA, apresentando um comportamento não linear, e é fortemente dependente da hidratação. (Polarização armazenada da ordem de 10-8 C/cm2). O DNA apresenta, em umidades elevadas (270 mg OH2/gDNA)constantes dielétricas elevadas, da ordem de 105, similar às dos ferroelétricos, mas com conceito diferente. Em baixas umidades (30 mg OH2/ gDNA) as constantes dielétricas são da ordem de 5. As curvas de hiterese, observadas com o circuito de Sawyer-Towêr (e citadas na literatura) são atribuídas a não linearidade no transporte elétrico. Esta não linearidade é também confirmada. O alegado comportamento ferroelétrico desapareceu quando utilizamos eletrodos bloqueantes. A alegada temperatura de Curie (60°C) é atribuída à forte desidratação que o material sofre, conforme verificado nas medidas de Pressão Termoestimulada.
Title in English
Not available
Keywords in English
Not available
Abstract in English
The bioelectret state of solid sodium desoxyribonucleate fibers was studied using the Thermally Simulated Depolarization, Thermally simulated Pressure and Isothermal Polarization Decay techniques. The bioelectret. Was found to present a space charge and non-linear behavior, and is strongly dependent on hydration (stored polarization as high as 10-8 C/cm2).At high relative humidity (270 mg OH2/gDNA) the DNA fibers show dielectric constants as high as 105, similar to those of ferroelectrics but with a different conception. The dielectric constant is only 5 at low hydration (30 mg OH2/ gDNA). The histeresis curves that are observed with Sawyer-Tower circuit (and frequently mentioned in the literature) are ascribed to the non-linear current voltage relations. The alleged ferroelectric behavior disappears when blocking electrodes are used. The alleged Curie temperature (60°C) is found to be caused by the strong dehydration that occurs at this temperature, as measured by the thermally simulated Pressure technique.
 
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Publishing Date
2015-03-16
 
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