We developed a quantitative measurement technique using atomic force microscopy (AFM) to study the effects of both DC and AC external electric fields on the forces between two dielectric microspheres. In this work we measured the DC and AC electric field-induced forces and adhesion force between two barium titanate (BaTiO?) glass microspheres in a low humidity environment by this technique. The objective here is to find out the correlation between these measured forces and applied field strength, frequency, and the separation distance between the two spheres was studied. Since the spheres would oscillate under an AC field, the AC field-induced force was divided into dynamic component (i.e., time-varying term) and static component (i.e., time-averaged term) to investigate. The oscillatory response occurs at a frequency that is twice the drive frequency since the field-induced force is theoretically proportional to the square of the applied field. This behavior can be observed in the fast Fourier transformation (FFT) spectra of the time series of the deflection signal. The magnitude of the vibration response increases when the frequency of the drive force is near resonant frequency of the particle-cantilever probe. The amplitude of this vibration increases with proximity of the two particles, and ultimately causes the particles to repeatedly hit each other as in tapping mode AFM. The effect of the Maxwell-Wagner interfacial relaxation on the DC electric field-induced force was discovered by monitoring the variation of the field-induced force with time. The static component of the AC electric field-induced force does not vary with the applied frequency in the range from 1 to 100 kHz, suggesting that the crossover frequency may equal to or less than 1 kHz and the permittivities of the BaTiO? glass microspheres and medium dominate the field-3 induced force. The AC field-induced force is proportional to the square of the applied electric field strength. This relationship persists even when the separation between the spheres is much smaller than the diameter of the microspheres. The large magnitude of the force at small separations suggests that the local field is distorted by the presence of a second particle, and the continued dependence on the square of the field but the measured force is much larger than the theoretical results, suggesting that the local electric field around the closely spaced spheres is distorted and enhanced but the effects of the local field distortion may have not much to with the applied electric field. Compared with the calculated results from different models, our results demonstrate that the field-induced force is much more long-range than expected in theory. In addition, the DC field-induced adhesion force is larger than the AC field-induced one due to the interfacial charge accumulation, agreeing with the discovery of the Maxwell-Wagner interfacial relaxation effect on the DC field-induced force. No obvious correlation between the field-induced adhesion and the applied frequency is found. However, both the DC and AC field-induced adhesion forces display the linearity with the square of the applied electric field strength as well. / Master of Science

O trabalho tem como tema central a Companhia de Aprendizes-Marinheiro de Santa Catarina, instituição instalada no ano de 1858 nas cidades de Desterro e Laguna. A abordagem sobre a Companhia tem como pretensão compreender as estruturas de poder que estiveram envolvidas com a instituição, em uma conjuntura de rearranjos do Estado Monárquico após o Período Regencial. Essa investigação sobre as estruturas de poder relacionada à promoção da Companhia de Aprendizes-Marinheiro revela agendas políticas desdobradas desde o processo de Independência do Brasil voltadas, em um primeiro momento, para a criação de forças de repressão através dos alistamentos militares, seguidos, de uma profissionalização dos trabalhadores marítimos como forma de estabelecer um contingente militar condizente com as necessidades do Estado imperial. Nesse sentido, a inserção da Companhia de Aprendizes- Marinheiro, reacende debates historiográficos, nos quais, o federalismo, ou os poderes descentralizadores do Império, tem parte importante no funcionamento dessa instituição militar. / The main theme of this research is the Companhia de Aprendizes-Marinheiros de Santa Catarina (Company of Marines Apprentices of Santa Catarina), an institution founded in the year of 1858 in the cities of Desterro and Laguna. The approach regarding the Companhia is to understand the structures of power that were involved with the institution, in a conjuncture of rearrangements of the Monarchical State after the regency period. This investigation on the power structures related to the promotion of the Companhia de Aprendizes-Marinheiros reveals political agendas deployed since the process of Independence of Brazil. Agendas that initially aimed at creating forces of repression through military enlistment, followed by a professionalization of maritime workers, as a way of establishing a military contingent consistent with the needs of the Imperial State. In this sense, the insertion of the Companhia de Aprendizes-Marinheiros revives some historiographic debates, in which federalism, or the decentralizing powers of the Empire, plays an important part in the functioning of this military institution.

Abstract This study aims to measure the flow field distribution in a microchannel with different heights adjusted. Two different materials, PDMS and Coverglass, were used to observe the flow velocity distribution change resulting from the difference in Zeta potential. The velocity distribution data were also obtained. In the experiment, 1¡Ñ TBE buffer solution with viscosity of 1 cp was used with the electric field intensity controlled under 5, 7.5 and 10 kV/m, respectively. Micrometer resolution Particle Image Velocimetry (£gPIV) was used to measure partial velocity distribution in order to explore the hydrodynamic stretch effect on DNA molecules when the microchannel, where the solution was placed, was adjusted to different heights. This study also statistically analyzed the stretch length distribution of DNA molecules in the microchannel and calculated the time of DNA molecule deformation and stress relaxation time in order to understand the stretch condition under different heights as well as the stretch and deformation of DNA molecules in microchannels.

O trabalho tem como tema central a Companhia de Aprendizes-Marinheiro de Santa Catarina, instituição instalada no ano de 1858 nas cidades de Desterro e Laguna. A abordagem sobre a Companhia tem como pretensão compreender as estruturas de poder que estiveram envolvidas com a instituição, em uma conjuntura de rearranjos do Estado Monárquico após o Período Regencial. Essa investigação sobre as estruturas de poder relacionada à promoção da Companhia de Aprendizes-Marinheiro revela agendas políticas desdobradas desde o processo de Independência do Brasil voltadas, em um primeiro momento, para a criação de forças de repressão através dos alistamentos militares, seguidos, de uma profissionalização dos trabalhadores marítimos como forma de estabelecer um contingente militar condizente com as necessidades do Estado imperial. Nesse sentido, a inserção da Companhia de Aprendizes- Marinheiro, reacende debates historiográficos, nos quais, o federalismo, ou os poderes descentralizadores do Império, tem parte importante no funcionamento dessa instituição militar. / The main theme of this research is the Companhia de Aprendizes-Marinheiros de Santa Catarina (Company of Marines Apprentices of Santa Catarina), an institution founded in the year of 1858 in the cities of Desterro and Laguna. The approach regarding the Companhia is to understand the structures of power that were involved with the institution, in a conjuncture of rearrangements of the Monarchical State after the regency period. This investigation on the power structures related to the promotion of the Companhia de Aprendizes-Marinheiros reveals political agendas deployed since the process of Independence of Brazil. Agendas that initially aimed at creating forces of repression through military enlistment, followed by a professionalization of maritime workers, as a way of establishing a military contingent consistent with the needs of the Imperial State. In this sense, the insertion of the Companhia de Aprendizes-Marinheiros revives some historiographic debates, in which federalism, or the decentralizing powers of the Empire, plays an important part in the functioning of this military institution.

O trabalho tem como tema central a Companhia de Aprendizes-Marinheiro de Santa Catarina, instituição instalada no ano de 1858 nas cidades de Desterro e Laguna. A abordagem sobre a Companhia tem como pretensão compreender as estruturas de poder que estiveram envolvidas com a instituição, em uma conjuntura de rearranjos do Estado Monárquico após o Período Regencial. Essa investigação sobre as estruturas de poder relacionada à promoção da Companhia de Aprendizes-Marinheiro revela agendas políticas desdobradas desde o processo de Independência do Brasil voltadas, em um primeiro momento, para a criação de forças de repressão através dos alistamentos militares, seguidos, de uma profissionalização dos trabalhadores marítimos como forma de estabelecer um contingente militar condizente com as necessidades do Estado imperial. Nesse sentido, a inserção da Companhia de Aprendizes- Marinheiro, reacende debates historiográficos, nos quais, o federalismo, ou os poderes descentralizadores do Império, tem parte importante no funcionamento dessa instituição militar. / The main theme of this research is the Companhia de Aprendizes-Marinheiros de Santa Catarina (Company of Marines Apprentices of Santa Catarina), an institution founded in the year of 1858 in the cities of Desterro and Laguna. The approach regarding the Companhia is to understand the structures of power that were involved with the institution, in a conjuncture of rearrangements of the Monarchical State after the regency period. This investigation on the power structures related to the promotion of the Companhia de Aprendizes-Marinheiros reveals political agendas deployed since the process of Independence of Brazil. Agendas that initially aimed at creating forces of repression through military enlistment, followed by a professionalization of maritime workers, as a way of establishing a military contingent consistent with the needs of the Imperial State. In this sense, the insertion of the Companhia de Aprendizes-Marinheiros revives some historiographic debates, in which federalism, or the decentralizing powers of the Empire, plays an important part in the functioning of this military institution.

Im Rahmen der vorliegenden Arbeit konnten Einflüsse magnetischer Felder, insbesondere mit hohen Gradienten der magnetischen Flussdichte, auf Korrosionsprozesse am Beispiel Eisen quantifiziert und deren Wirkungsmechanismus erklärt werden. Als ein besonders in technisch relevanten gering konzentrierten sauren wässrigen Lösungen bedeutsamer Effekt wurde eine sekundäre Wirkung der Feldgradientenkraft über den Mechanismus der Wahrung der Ladungsneutralität auf den pH-Wert an der Elektrodenoberfläche identifiziert. Somit konnte ein signifikanter Magnetfeldeinfluss auf die formal ladungstransferkontrollierte Korrosionsreaktion nachgewiesen werden. Um die komplexen Korrosionsvorgänge an mehrphasigen NdFeB-Magneten mit paramagnetischer intergranularer Nd-reicher Phase aufklären zu können, war zunächst eine vertiefte Analyse der freien und anodischen Korrosionsreaktionen des Neodyms notwendig. Die dabei gewonnenen Erkenntnisse erlauben den Magnetfeldeinfluss bei der Korrosion aufmagnetisierter NdFeB-Magnete zu verstehen.

Im Rahmen der vorliegenden Arbeit konnten Einflüsse magnetischer Felder, insbesondere mit hohen Gradienten der magnetischen Flussdichte, auf Korrosionsprozesse am Beispiel Eisen quantifiziert und deren Wirkungsmechanismus erklärt werden. Als ein besonders in technisch relevanten gering konzentrierten sauren wässrigen Lösungen bedeutsamer Effekt wurde eine sekundäre Wirkung der Feldgradientenkraft über den Mechanismus der Wahrung der Ladungsneutralität auf den pH-Wert an der Elektrodenoberfläche identifiziert. Somit konnte ein signifikanter Magnetfeldeinfluss auf die formal ladungstransferkontrollierte Korrosionsreaktion nachgewiesen werden. Um die komplexen Korrosionsvorgänge an mehrphasigen NdFeB-Magneten mit paramagnetischer intergranularer Nd-reicher Phase aufklären zu können, war zunächst eine vertiefte Analyse der freien und anodischen Korrosionsreaktionen des Neodyms notwendig. Die dabei gewonnenen Erkenntnisse erlauben den Magnetfeldeinfluss bei der Korrosion aufmagnetisierter NdFeB-Magnete zu verstehen.